ArchiveCategory Archives for "OTR Tires"
Co-authored by Mr. Len Hensel, BSME, MS-PDD Wheel Engineer and Keith Heeres
The tire indexing, tire slippage, or tire spinning on rim problem we are looking at is as it relates to off the road equipment used in earthmoving, construction, mining and other heavy equipment applications. Tires spinning on rims is commonly talked about in automotive, off road recreational vehicles, bikes and motorcycles. Same type problem occurs on the big machines as well but for similar and some different reasons. Tire indexing is the topical term we use in the off the road industry to discuss the problem with tires and wheels.
Many wheel loader operators have experienced situations when they are pulling out of an aggregate pile, the tires are moving but not going very fast. At this point, the operator then realizes that the tire is slipping or tire is spinning on the rim/wheel. The end result can be a chewed up tire bead area which is expensive to replace. Other issues can result that will impact the availability and productivity of the machine. For over the road type of applications, tire indexing can lead to air loss and ride disturbance complaints.
Tire indexing is a problem of all pneumatic tire assemblies that are used with any type over-the-road vehicles or off road equipment. Off road equipment with high engine power/torque is more prone to tire indexing. Typically this would be all sizes of wheel loaders, rubber tired wheel dozers, and container handlers just to name a few. Construction equipment has been noted as experiencing tire indexing but other off road applications such as agricultural, industrial and mining will experience tire indexing as well. Tire indexing has been observed with non-drive axle application such as quarry and large mining haul trucks. Tire Indexing can occur because of high braking forces/torques. A non-drive axle would typically be the front steer positions of a haul truck.
So, what is tire indexing? What causes it? How can this be limited or stopped? What can be done about it? In this article we will address some of these basic questions.
The definition that is used in this article is “the permanent circumferential rotation of one or more of the tire beads relative to the bead seat(s) of the rim”. Along with this, the tire is not slipping on the ground. The tire traction with the ground is able to transfer all the static and dynamic forces from the equipment.
Other terms are used in the off road applications. Some of the terms are:
· Rim slippage or tire slippage or tire slippage on rim
· Rim spinning or tire spinning or tire spinning on rim or wheel
These terms generally mean the same thing.
It is important to note that the wheel is typically bolted to the drive axle so it cannot slip relative to the machine hub. The movement we see is the tire slipping on the rim bead seats. For a person observing tire indexing from the side of the road, it appears that the tire is stationary and the rim/wheel is turning inside the tire. In this article, the tire is the component that is indexing relative to the equipment driveline.
Tire slippage occurs with agricultural tires used in tractor applications. The drive tires have some intended slippage (especially in all-wheel drive configurations) with this type of application while they are under drawbar torque. A certain amount of slip at the ground is needed for efficient operation of the tractor. This type of slip is not addressed in the article.
Tire indexing can occur with passenger tire and wheel assemblies as well. In this application the driveline and braking forces are causing the movement of the tire. The consequences of the tire indexing is ride disturbance (change of tire assembly balance, change in the radial runout) that the driver and passengers that feel inside the vehicle. This type of indexing is not the primary focus of this article. However, cause 1 & 2 discussed later in this article do apply to passage car application.
There is a style of rim mounting called “demountable”. In this design the rim is clamped to the hub of the driveline. With this type of mounting the rim can slip on the hub because of drive or braking torques. We are also not addressing this situation in this article.
Tire indexing is an axle end system issue. Important note: The word system is being used because we have individual components that must work together so the drive or braking torques is transferred through the equipment to the ground.
The basic system components (tires, wheels, hubs, brakes) must work together so the equipment can move or stop when needed. When one component of the system does not function properly, tire indexing can be one of the consequences. When you have a system issue, factors and characteristics influencing it can be a combination of characteristics and not just a single characteristic.
Before we discuss the causes and factors that contribute to off the road tire indexing, we need to review the basics of tires and wheels.
The diagram on the right shows a typical cross section of a radial tire.
When we make mention of “the bead”, “bead area”, “Lower tire bead area” we are referring to item #1.
· When referring to the tire bead seat area we are referring to item #13.
Tires used in off road applications have several types of construction configurations. While many people know what these are, we will review them here anyway.
Tires, regardless of the application, can be separated into two very broad groups, tube-type (TT) and tubeless (TL).
Tube-type tires are constructed with rubber and other materials such as steel, nylon, and polyester. Rubber is a porous material from an air migration standpoint. An example of this would be inflating a balloon until it is big and taught. If we let it stand for a few days it begins to shrink because the air inside is migrating through the rubber wall of the balloon. In the early days of the pneumatic tires a special compound was developed to prevent air migration from occurring. This became the material used for tubes. Tubes have been used in tires for over 125 years and are still used today in over-the-road and off road applications.
The tube is located on the inside of the tire and acts like a big balloon. A flap, which is also made of rubber, is placed between the bottom of the tube and the rim. The flap protects the tube from chaffing against the rim and provides support around the valve slot add area. The tube is inflated through a valve stem which is generally located at the bottom of the tube.
When tire indexing occurs, the tube will move along with the tire because of the frictional forces between the tire and the tube. The valve stem however will not move and at some point the valve will separate from the main tube and cause immediate loss of air.
The tubeless tire was first introduced around 1947. This marked a significant technology advancement to reduce the tire system complexity and improve the reliability of the tire and wheel assembly. The tubeless tire was introduced into the off road applications around 1955. TL tires eliminated one field issue with tire indexing - the shearing off the valve stem. While indexing can still occur, the valve stem is part of the rim now that when the tire moves; it does not affect the valve stem. More than 90% of the tires produced today are tubeless construction. However, tubes can still be installed in these tires for special situations.
The next broad grouping of tires we will discuss is the type of internal tire construction. Each of the construction types we will discuss below can be made as a tube type with tubeless features. But as noted above, the vast majority of tires are made for tubeless operation.
Tires were originally made with rubberized cotton fabric (ply) to provide strength to the tire to resist the air pressure and support the load on the tire. Several ply layers were used with each ply having a different angle relative to each other. This allowed for the proper strength in the tire to be achieved. The plies are wrapped around to the tire bead. With this type of construction 1, 2 or 3 bead bundles will be used depending on the number of actual plies used in the construction. Modern materials used for the fabric plies have allowed the actual number of plies to be reduced, but the strength of the tire has increased. Bias tires tend have a stiff construction and provide good lateral load resistance.
Lateral loads (or forces) are those that push or pull against the sidewall or lower bead area of the tire. Typically these forces are caused by:
- Dynamic forces from maneuvering corners or other turning events
- Travelling on the side of an incline
- Dynamic forces from high center of gravity operations such as material lifts
When multiple bead bundles are used, a wide tire bead aids in resisting tire indexing because of a larger surface area to transmit the torque. Bias tires have a unique pressure pattern in transferring loads and pressures in the rim. More pressure is applied to the bead seat surface as compared to the radial tire construction. This also aids in resisting indexing.
The radial tire construction was introduced to the market place in in the 1950’s. This construction provided many performance improvements compared to bias tires and has allowed performance capabilities to be expanded beyond the limitations of bias tire construction.
Tire durability, TKPH (Tonne kilometer per Hour) ratings and other characteristics improved dramatically. Changes in the manner in which forces are transmitted between the tire and the rim and the lower lateral stiffness characteristics tended to cause an increase in tire indexing.
The main function of the rim is to provide support to the tire and to facilitate the passing of forces from the driveline of the equipment to the tire. There are several construction styles of rims used in off the road applications:
There are standard and heavy duty designs in the market place. Standard or heavy duty designs as it relates to the thickness of the steel material used to form the rim and the overall profile design of the rim. Standard duty designs are typically used in various agricultural applications. The heavy duty designs are typically used in construction applications (motor graders, small front end loaders) and high load applications such as harvester and logging applications. All designs are intended to be used with tubeless tires. However, inner tubes can be used. The rim profile has 50 taper for the bead seat surface to create a tight fit with the tire bead area. Knurling is included with some rim sizes to address tire indexing. Because this is a single piece construction, there are no loose components that exhibit circumferential movement.
These rims are commonly referred to as “flat base” style. They are typically used with tube-type tires in rim diameters from 15” to 24”. Normally a tube and flap is used with the tire to inflate the tire. The fixed flange side of the rim allows for some interference fit with the tire bead. Typically, there is no tire bead interference fit with the removable side of the rim. There is a limited ability to resist tire indexing. There some tube type rim designs that can be converted to a three piece configuration that are used for heavy load applications. Some of the rim designs can be converted to use tubeless tires if an “L” style polymer sealing ring is used.
There is lightweight and heavy duty versions used in the marketplace with the same basic components. These designs are intended to be used with tubeless tires. An O-Ring groove has been added to the gutter band so that an O-Ring can be added to create a tubeless seal. The rim profile has 50 tapers for the bead seat surfaces to create a tight fit with the tire bead area. Knurling is an included feature for the heavy duty design to help in reducing tire indexing.
There are standard and heavy duty rim and wheel designs in the marketplace that use the same basic components. These designs are intended to be used with tubeless tires. An O-Ring groove is used in the gutter band so that an O-Ring can be used to create a tubeless seal. The rim profile has 50 tapers for the bead seat surfaces to create a tight fit with the tire bead area. Knurling is included to help reduce tire indexing. The side flanges are separate components included for design flexibility.
In several of the above rim styles, a feature called knurling has been mentioned. Knurling is a lateral serration feature that added to the bead seat surface to assist is resisting the tire bead from indexing. A good way to visualize the function of knurling is that it provides a means for the tire bead area to grab onto an otherwise smooth surface of the rim bead seats. Specifics of the knurling and when they are recommended to be used are specified by various recognized industry standards bodies such as the Tire & Rim Association (TRA).
With multi-piece rim and wheel designs, the loose components resist circumferential movement through frictional force resistance only. In many cases this is not sufficient to keep the components from rotating. Mechanical locking features are used with all high torque applications. Two basic locking systems used on off road rims and wheels are shown below.
This is the simplest version and was the first one used in the industry. Notches are cut in the bead seat band and gutter band. A lug or driver is attached to the lock ring. The lug fits into the notches so the bead seat band cannot rotate relative to the rim. Notching of the rim components has an impact on the strength of these rim assemblies. Normally when this style of driver pockets is used the operating inflation pressure is limited to a maximum of 65 PSI (4.5 bar) or less.
Note – This tends to be the standard industry practice in North America. In other global regions end users are running at higher pressure levels
There are several versions of this style used depending on the strength that is needed for the application. One driver pocket is welded to the side flange (or bead seat band). A second driver pocket is welded to the outboard surface of the gutter band. A driver key is then placed in between to lock the side flange/bead seat band from circumferential rotation.
With five piece style rims, the flanges are free to rotate with the tire. A driver lug is welded to the vertical portion of the flange and two lugs are welded to the rim back band or bead seat band. These lugs fit and work together to keep the flange from rotating with the tire. Thus adding more resistance to tire indexing or slippage.
Tire indexing involves the Output End of the driveline system. We are defining the output end as the tire, wheel and hub/axle. All of the driveline power, all of the braking forces and all dynamic forces must be supported and transmitted by each element of the tire and wheel system. Each element of the system must then work in concert with each other so that all the forces are efficiently transmitted to the ground. The function of the tire and wheel system is:
The tire and wheel assembly is a pressure vessel. The amount of load that it will support is based on the air volume of the tire and the air pressure necessary to carry that load. The load index (LI) or ply rating (PR) of the tire defines the load capacity it can support. Important note: The rim must be chosen to match the tire capacity/capability.
In operation shock loads must be supported because of rough road surfaces, undulations of the road surfaces, a tire running over road debris and sudden loads being dropped into an equipment body or bucket. In many applications the tires are the only suspension system for the equipment.
Primarily turning forces when a piece of equipment is travelling around the work site. From a wheel perspective, turning (or twisting) generates the highest forces that the wheel assembly must support. This puts the greatest amount of stress on the wheel center as well as the bolts or studs holding the wheel to the hub. Other dynamic forces would be :
The dynamic and static forces from the equipment and driveline are passed through the flange and bead seat surfaces of the tire and rim interfaces noted as “A”.
There are no mechanical fastenings of the tire to the rim. Frictional forces generated by the inflation pressure on inside of the tire holds the tire in place and resists circumferential, transverse and lateral movement. More air pressure means more fictional force to resist the dynamic forces. Less air pressure means less resistive forces.
The bead seat area of the interface has additional features to aid in resisting indexing. The bead seat area of the tire is designed to have a certain amount of interference fit with the bead seat of the rim.
The interference is to create an air seal in the static and dynamic state and to aid in stopping circumferential and lateral movement of the tire bead areas. Knurling is an added feature to provide a mechanical means of holding the bead in place from circumferential movement.
Generally, the tire tread does not slip on the ground. While this can happen in emergency braking or other situation, the tire generally has good traction with the ground. Radial tires (seem to) have improved traction characteristics with construction and mining tires. The limitation of the tire and wheel system for transmitting torque to the ground is the tire and rim interface(s).
Anything that reduces the frictional forces of the inflated tire will allow or contribute to tire indexing or tire slippage on the rim. Even with ideal conditions between the fit of the tire to the rim bead seat surfaces indexing can still occur.
One of the simplest issues that can contribute tire indexing is tire air pressure that is too low. As mentioned above, frictional forces between the tire and rim bead area resist the dynamic forces that cause indexing. If the air pressure is too low, then the tire can move. Low air pressure can occur because of poor maintenance practices of a work site, or operating the tire with air pressures that are too low for the application. The following practices will help to avoid or minimize tire indexing.
Another universal cause regardless of the application is using too much tire lubrication when fitting the tire to the rim. A tire lubricant is used to reduce the frictional resistance of the tire beads on the rim bead seat surfaces so the tire beads will slide into the correct position. It is important to follow the tire manufactures tire mounting recommendations. It is also important to:
If too much lubricant is not good, insufficient amount of tire lubricant can be equally bad. If the tire does not slide onto the bead seat surface of the rim, then the tire beads may not be positioned as intended. If the tire beads are not in the correct position then the performance and durability of the tire will be impacted. Additionally:
As mentioned above, it is important to follow the tire manufacturer’s mounting recommendations and procedures.
Assuming we have used the correct amount of lubrication, the next issue in mounting the tire that can contribute to indexing is a tire bead that is not properly seated. It was noted above, that insufficient lubrication can keep the tire from seating. Insufficient air pressure (too low) to “seat” the beads can contribute to tire indexing because the tire bead will not be in the correct position on the rim impacting the interference fit and resulting in insufficient frictional forces resisting drive or braking torques. Most tire bead areas are designed to have an interference fit. Extra force is needed to push the tire into the correct position. The “seating pressure” is generally higher than the operating pressure for the tire. Seating pressure vary depending on the type of tire.
During the mounting process, before the assembly is inflated the driver keys must be installed. The outboard drivers are intended to stop the rim components from rotational movement. Many times, the keys are missing to begin with and they are missed as one of the steps for mounted a new tire on the rim.
With any problem solving activity, all aspects of the issue should be evaluated.
* Used with permission from Tire and Rim Association.
Below is a method used for measuring the rim bead seat diameters. Not typically available at the field level but is used at the factory level to verify dimensions.
* Used with permission from Tire and Rim Association.
* Used with permission from Tire and Rim Association.
Every brand of tire is designed and engineered to provide excellent durability and service life for the desired application. Each Engineering group has their own set of design standards and design principles that they believe are correct for a particular tire/application. The resulting differences can be observed in how the tires perform in the field and fit to the bead seat surfaces. With tire indexing, some brands or sizes within a brand can be better choices to minimize or eliminate tire indexing for the application. Factors that have an influence on tire indexing are:
The manner in which the equipment is operated can have an influence on tire indexing.
Equipment manufactures make a good attempt to have the various components matched so the operators have a good experience operating the equipment. However driveline efficiencies and tire technologies have improved, the drive and braking torques being passed to ground has increase. This is good for productivity of the equipment, but the forces being applied can be greater than the tire and rim interface can resist. In these situations it may be necessary to consider moving to an assembly with a larger bead diameter.
Tire indexing is an action that normally occurs in such small, minute amounts that it can be virtually undetectable unless the tire and rim components are marked on the tire, flange, bead seat band and rim/wheel. This way you can witness the physical movement of the tire and the wheel components.
The tire, side flange, bead seat band gutter band and hub have been marked prior to a tire indexing study. The paint marks are all aligned at the start of the evaluation.
A tire and wheel assembly component after the assembly has been used.
Tire indexing is virtually impossible to stop unless all the factors that cause it are addressed properly. The "tire is going to move no matter what you do". The question is, “how much”?
The term “fretting damage” had been mentioned above as a consequence of tire indexing with multi-piece rim and wheel assemblies. Fretting is an engineering term which describes the damage to contact surfaces when they are subjected to contact pressures and exposed to repeated movement (slippage) or vibrations. The movement does not need to be large, repeated minute motion is sufficient for fretting damage to occur.
Mr. Len Hensel, BSME, MS-PDD
Len has over 39 years of industry experience in providing wheel system solutions for the mining, construction and agricultural applications. He has worked extensively with the entire major off road equipment manufacturers and off road tire (OTR) companies to provide designs that meet the needs of new applications, pushing the envelope for greater load capacity and durability. He has worked in leadership positions in off the road wheel industry new product development, application engineering, new design validation, research and development projects, and quality assurance. He is a member of the Society of Automotive Engineers (SAE), participated in development of international standards (ISO) related to off the road wheels, and a past member of the Tire and Rim Association (TRA) representing the rim and wheel industry manufacturers.
Contact: [email protected]
This is a very long information packed article or post. I decided to cover it in one large post rather than several smaller ones. The Quick Navigation links above make it easier to navigate the relevant sections of the article you want to read. While I will mention some brands of products and provide links to those, they are for information purposes only. I am not endorsing any one product in this article.
The main goal for the owners, operators and mobile equipment managers is keeping their fleet of equipment working to maximum performance to meet production quotas. At the same time they want to minimize operational expenses and maximize their companies profit. Minimizing equipment maintenance costs is a top priority anywhere you work. Tire expenses are one of the top expense items for off the road equipment that roll on wheels and tires. Unscheduled equipment downtime due to tire failure is something these stakeholders want to minimize and is an issue they you can do something about. Downtime from flat or damaged tires can be extremely costly to fix as well as create additional problems such as backlogs in continuous service operations and service interruptions in mining and quarrying operations. Tires for them are a recurring expense as well and they have dramatic effect on total operating and daily productivity.
These stake holders in charge of rubber tired off road vehicles want to:
Commercial tire dealers are essential partners in accomplishing all these goals for them. Their machines don't perform well unless the tires and wheels on their machines are in optimal condition to do the job.
When the issue tire selection and flat proofing tires comes up there are several approaches to consider.
We're going to look at the issues like this:
If you are trying to solve the problem of how to make sure your off the road machine doesn't suffer from flat tires, how do you address the problem of tire flat proofing and solve it using the best solution at the least expensive cost?
First we need to ask ourselves some questions. For the moment, we will disregard tire tread considerations and just focus the issue of how to eliminate flat tires on off road vehicles. We need to understand and evaluate what your options are. You need to have a handle on all your machine and tires issues and consider how to address them most effectively. We need to evaluate how you would address the problem with a piece of equipment like a skid steer loader, a wheel loader, a forklift, a specialized piece of material handling equipment used in a factory environment or a piece of military equipment that must ready for fight or flight can be very different.
Let's consider each option one at a time.
There are many benefits of choosing to use pneumatic tires. Regardless of the tires design or application, all pneumatic tires are designed to:
The benefit of using pneumatic tires is they are made in a wide range of common tire sizes to fit standard wheels & rims, section widths, overall tires diameter, specialized rubber compounds, tire profile, tread designs, bias or radial construction and air pressure ratings. They usually offer the best choice for the combination of economy and comfort. They can run in many applications and are capable of performing equally well indoors and outdoors, and can be used in heavy and light duty applications. New tires are widely available from a variety of tire manufacturers, price and quality ranges. Tire and wheel packages can be easily be put together to fit nearly any machine.
The case against using pneumatic tires is simple. These tires must hold air to work. Tire air pressure is a key component of a mounted tire and wheel assembly. Maintaining that air pressure is key to the tire being able to perform as expected. Pneumatic tires are more easily damaged by nails, screws, rebar, and other hazards common on construction sites. Owners and users must check and maintain their tires’ air pressure consistently. The biggest cause of premature pneumatic tire failure is the failure to maintain optimal tire pressure.
So how do we make a pneumatic tire flat proof and still enjoy the benefits of a pneumatic tire?
Tireliner is a permanent, self-healing, urethane rubber sheet that is securely adhered directly to the inside of the tire casing of a pneumatic tire. Tireliner works by self-sealing over cuts, punctures and penetrating objects, and will prevent tires from going flat if punctured or cut by objects up to 1/4” in diameter. So objects like nails, screws, sticks, small metal objects and thorns will not leave a hole that will cause the tire to loose air pressure.
Tireliner offers sidewall protection as well as protection for the tread areas of the tire. The patented material actually allows the liner to immediately close over the zone of penetration and completely fuse, thus, air pressure loss is prevented.
Tire balance and structural integrity are not affected by the addition of the Tireliner material. Tireliner is excellent for applications where added weight may be undesirable or will create a problem. Tires lined with Tireliner are recappable and repairable. It is unaffected by temperature extremes in hot or cold climates, or tire air pressure.
Tireliner is a puncture sealing system that offers true sidewall protection as well as protection for tread areas. It provides a balanced, uniform thickness of self-healing rubber. It is also the only available system that conforms to any size geometry of tire and lasts the lifetime of the tire.
Tire balance and structural integrity are not affected by the addition of the tire liner. Tireliner was originally developed for the military and has been in commercial use for many years now.
Limitations of Tireliner
Tireliner can only be used in tires that are 24” or less in diameter. This size limitation is because the equipment available to apply the urethane material won’t accommodate large tire sizes.
Various companies around the world are capable of tyre lining. Nearly any tire in the size range their equipment can handle can be lined. Tyre liners work best when you purchase a new tire with the liner installed at the factory.
If you already have tires that you want to have lined, there are services where you can send the tires to get this done and have them sent back to you ready to mount back on wheels to be put back on machines.
Liquid tire sealants come in several formulations for both consumer and commercial tire uses. They have been on the market for several years. They are intended for quick and fast tire repairs when you don’t have time or you are not in a suitable area for changing tires.
There is some controversy about using many of the consumer grade tire sealers. Why?
First they are only a temporary fix. Intended to get you from where you stop to attend to your flat tire, to the nearest place you can get your tire fixed or replaced. They are not spare tires in a can and they are not a permanent fix. They have a very limited service life.
They are intended to fix small tire punctures of a ¼” or less in the tread face of the tire. Not in the sidewall of the tire.
Using these consumer grade sealers can invalidate your tire warranty. You need to investigate that before you use them.
They are not intended to be used in high performance tires at high speeds of travel.
Most commercial tire dealers hate them because of the mess they make and the difficulty of cleaning up the tires to patch them. Not to mention the mess they can make of the wheels and potential to damage TPMS systems.
Consumer grade sealers work fine for some applications but are not recommended for others. If used in car tires, some commercial tire dealers will add extra charges to a customer’s bill for the additional labor to clean up tires and wheels. While other dealers will decline entirely to work on tires that have been sealed with some of the commercial sealers.
Some of the consumer tire sealers are intended to work with ATV, consumer grass mowing equipment or smaller tires.
Some of the consumer tire sealants are manufacture specific and intended for OEM automotive use in vehicles and tires those manufacturers recommend.
Certain tire sealer kits are paired with small portable compressors and a sealant for repair of a flat. These are considered to be emergency tire inflation kits.
The aerosol can tire sealers can leave a sticky liquid mess in the tire that settles to the bottom of the tire when the vehicle is parked. Then as the vehicle reaches high speeds it will cause the tire to be unbalanced and create a lot of vibration. Depending on the brand the sealers can also be made of flammable materials. Read the labels and use them with care.
Commercial grade tire sealants are a different breed apart. The use of commercial grade sealants in tires is a preventative maintenance measure you can take to eliminate pneumatic tire flats from punctures to the tire up to ½” in size. These commercial grade sealants are designed and intended to be used continuously in the tires providing all the benefits they were designed for.
Liquid tire sealants are pumped into the tire through the valve stem. They coat the inside of the tire so they are ready to do their job instantly should an object puncture the tread creating a hole the needs to be sealed immediately. They will repair and prevent flat tires, seal minor cracks in inner wall of the tire, and continuously self-seal punctures. They can also stop valve leaks and leaks between the bead and rim.
There are several manufactures that make these commercial grade sealants. Some are made with Kevlar® or aramid fibers in the liquid formula. Others are using state of the art nano-technology to clot and fill the puncture hole. While not all tire sealants are the same as made by the manufacturers, the main benefits are:
DuPont™ Kevlar® The DuPont™ and all products denoted with ® or ™ are trademarks or registered trademarks of E. I. du Pont de Nemours and Company or its affiliates.
Like consumer grade tire sealants, there are differences in the commercial sealants as well. You will find lower grade products and premium products that have been tested and approved by OEM tire manufacturers, and independent tire and rubber testing labs. You also need to check and see if the commercial sealant you might be considering is safe for TPMS if you are using them. You also want to make sure the sealant you might be considering is non-flammable and how easily it is to wash out or clean up.
So far we have talked about how you can flat proof and make your pneumatic tires puncture resistant from the inside of the tire. What about protecting your pneumatic tires from the outside?
Couple ways to do that.
1. Use Tire Protection Chains to give your tires a coat of armor.
2. Use Tire Saver Shields ™ or other similar products to give your tires a side wall “shield”.
1. Protect tire treads and sidewalls from abrasions, cuts, gauges and punctures. These chains can extend the life of your expensive rubber tires from as many as 4 to 10 times (according to manufactures literature). They come in several interlinking ring systems, hardness ratings and ring or mesh designs. Because of the way they are designed, the chains are flexible and can adjust the tire as it moves over the operating surface while protecting the tires from sharp edged stones and abrasive surfaces.
In steel making and slag handling applications the Tire Protection Chains help to protect the tires from the intense heat of red hot steel slag. This slag material can reach temperatures approaching 2,200 degrees Fahrenheit. Wheel loaders have to handle and navigate around large and solid scrap pieces. The chains will protect the tires from punctures, burning tires and very abrasive ground conditions.
Tire Protection Chains can also be custom designed for specialized applications. All you need to do to fill out a form and contact the company with your requirements and an expert in chains will provide you with a personal consultation.
2. Tire chains give tires greater traction in icy, frozen, snowy or muddy conditions. When you’re having to deal with steep inclines, spinning wheels and season weather conditions, tire chains can be a critical safety item for heavy equipment.
Earthmoving tires are typically the most expensive cost of ownership item on wheel equipment and are very sensitive to cuts, punctures and other damage. Tire chains are indispensable when used on wheel loaders and underground mining equipment involved in hard rock mining and quarrying. Tire protection chains are also very beneficial in protecting machines involved in steel making, scrap handling and demolition work.
Unprotected tires can be worn out and deteriorate quickly when used in the above mentioned work environments. Tire protection chains offer and optimum level of protection to reduce tire maintenance costs.
Important note: Tire Protection Chains are not inexpensive. They are however reusable, repairable and they do an excellent job of protecting and extending the life of your rubber tires. And, they will add more weight to your wheel and tire assemblies. That added weight can be an advantage or disadvantage depending on your equipment owners perspective.
Main suppliers in the industry are:
Tire Saver Shields are the result of years of work creating tire sidewall protection for rubber tired military equipment. The goal of the product is to prevent and protect tires from “non repairable” sidewall damage that would occur from striking or moving against the sharp edges of rocks, metal objects or other objects that could be snagged by the tire sidewall. The construction of the product is also fire resistant as well. Remember its origin was military use.
Tire Saver Shield ™ is a registered Trade Mark of Hutchinson Industries.
Tire Saver Shields are available in several common tire sizes. Larger sizes for earthmover tires are being produced as well.
Tire Saver Shields are attached to wheels that mount the tires via a ring welded to the wheel flange. After the tire is mounted on the wheel and inflated the Tire Saver Shield is bolted to the attaching ring. The Tire Saver Shield conforms to the profile of the tire. It creates and heavy barrier between the tire sidewall and any potential damaging object the tire may encounter that could damage or puncture it.
How do you know Tire Saver Shields will work for you and your application?
If you are tracking your tires and documenting how and why you have lost tires, you just need to figure out how many tires you have lost due to “non-repairable” tire sidewall damage. Look for where you lost tires that still had useable tread, but the tire sidewall failed and you had to scrap a tire that would had still useful tread life. Those are the costly failures you want to eliminate. Tire Saver Shields have been proven to enhance the survivability of off the road tires in several applications. They are very effective in mining, quarrying, and heavy lift industrial forklift applications.
Tire Saver Shields are not inexpensive and require qualified installation. If you would like a consultation about how Tire Saver Shields can help you, give me a call.
Hutchinson is not the only company that makes a tire shield. The Rud company make a product they call the SideFlex.
Like the medieval knights of old, you can always outfit your expensive off the road tires with a new coat of armor and equip them with a shield to ward off the potential hazards of your work site that would destroy your tires.
These tires are almost completely flat proof, puncture resistant and cut resistant. There are specialized applications they are suitable for, size limitations, load and speed limitations and heat buildup issues.
Some of the most expensive, highly engineered and well constructed tires in the world are aircraft tires. Every aircraft tire is entirely handmade and very carefully constructed and inspected to the most stringent requirements of the FAA standards. There is no such thing as a bad aircraft tire which is why brand new they are very expensive. In fact they are overbuilt to withstand the unexpected conditions they may be exposed to. Blowouts on aircraft tires almost never happen. It they do, it us usually related to low inflation pressure of a tire or hitting a piece of debris on the runway.
General aviation tires almost always are built as bias-ply construction tires. Retreaded aircraft tires is an industry standard for commercial airliners and military aircraft. Aircraft tires are very different from consumer grade tires in this big way. Most aircraft tires on commercial airliners are pressurized to 200 PSI with nitrogen rather than air. Your typical car tire operates at between 30 to 40 PSI and are pressurized with air.
Aircraft tires are designed for:
Aircraft tires are made of very thick rubber, extra heavy sidewalls, heavy nylon ply cords and are formulated to resist all kinds of wear, abrasion, cutting, cracking and heat build up.
Since these tires are so heavily plied they are “almost” entirely puncture proof. This feature makes them very popular for a wide range of uses where the tires must be pneumatic. They are ideal for applications from agriculture, forestry, commercial mowing, mining, industrial uses, steel mills and scrap yards.
Aircraft tires are also easily recapable. The aircraft unique treads are buffed off and commonly used treads normally found on conventional tires can be molded right back on them. This can be done over and over again so long as the tire casing us undamaged and still useable. A multitude of tread designs and rubber compounds can be remolded to the aircraft tire casing.
Aircraft tires come in specialized sizes and require custom wheels to mount them. They could require industrial bolt together or 3-piece lock ring style wheels to mount them. If you don’t have these wheels already, complete mounted tire and wheel assemblies are available or can be custom built for your machine application.
These specialized tires are almost always tube type tires so they will require a tube and flap for your wheel. Those can be easily supplied with your assembly as well.
Size limitations are another consideration for aircraft tires. Certain sizes are difficult to get due to changes in the commercial and military aircraft markets. Some of the largest tires are made to fit military heavy bombers and there are only so many of those types of aircraft in service around the world.
By USAF Photo by Technical Sergeant Robert J. Horstman [Public domain], via Wikimedia Commons
Since these repurposed tires are built for high load carrying capacity at very high speeds (for example take-off and landing speeds of 150 to 200 mph), when you drop the operating speed of these tires you get extremely high load carrying capacities.
If you want to get added puncture resistance, you can always add one of the commercial grade liquid tire sealants to the aircraft tires and add all the benefits the products provide as well. Double up the protection. Some vendors of air craft tires do that when they supply the full tire and wheel assembly anyway.
The use of run-flats in consumer vehicles is and has been very controversial. Some high-end automobiles have offered vehicles with run-flat systems, but they are not widely used. They just never caught on and were very expensive compared to other methods of flat proofing and puncture resistance.
Run-flats and bead locks however in military vehicles are widely used and provide the benefits of making the wheel and tire assembly essentially bullet proof. The tire can be punctured with a bullet or projectile and the air will be lost, but the run-flat system takes over so the vehicle can continue to fight or drive away quickly. Run-flat systems for military equipment are proven to give the vehicle the ability to travel distances such as 20 miles to get the military crew out of the danger zone.
Beadlocks are also very popular for owners of off road machines (like ATV's, RV's, jeeps and trucks) and in off road racing.
Internal bead locks are different from run-flats in that they are bolted together or pressed into the inside the wheel to lock the tire beads in place when the tire loses air pressure. The vehicle can continue to roll (at a reduced speed) on the tire a small distance temporarily.
I mention run-flats and bead locks because they are a method of flat proofing pneumatic tires. For example, if you have a vehicle that has the ability to use wheel and tire sizes made for military type equipment and you can acquire surplus tire and wheel assemblies with the run-flats and bead locks, you can use these to flat proof your equipment. Naturally there are size limitations which these products are available in such as 20”, 21” and 24” diameter. And the wheels are specialized as well.
Examples where you may encounter these types of flat proofing methods applied to the tires and wheels are specialized trucks and emergency response vehicles like you might find are airports. However, most applications are military related.
Another feature of these wheel types that can be added are Central Tire Inflation Systems (CTIS). They can keep the tires continuously pressurized so long as the tire puncture or leak is not real large.
I am going to cover two methods of flat proofing pneumatic tires by removing all the air pressure from the tire. Polyurethane foam fill is a common method that most everyone knows about. But Trojan Tire Liners is not so widely known even though it has been around for many years. Each approach is different and has its own benefits and draw backs.
Polyurethane foam filled tires are completely flat proof, puncture proof and to a limited extent cut resistant. There are a large number of applications it is suitable for, size limitations, load and speed limitations and heat buildup issues. Foam filled tires are air-less tires so there is no air pressure to contend with. It is fairly easy to get set up to do tire foam filling. You just have to contact a polyurethane foam supplier and sign up, by the necessary equipment, buy the liquid polyurethane components you need, have a suitable environment to do the work, get trained on doing foam filling and start selling the service.
Foam fill for tires is also known as “tire fill” or “poly fill” and those terms can be used synonymously in the context to pumping polyurethane foam into tires for flat proofing. The use of polyurethane foam fills in tires has been around since 1970 so there is a great deal of experience with the product. Polyurethane foam fill for tires is composed of a two-part liquid polymer (Part A and Part B formulas) that is pumped into the tires through a specialized pump that blends the two components. In the pump the Part A and Part B liquid compounds are mixed and a chemical reaction begins to take place. Prior to pumping foam into the tire, the air is drained out of the tire and an air escape hole is drilled into the tire. This hole is later plugged when the tire is full of foam and has displaced all the air. The blended liquid material is pumped into the mounted tire/wheel assembly through the valve stem with a special foam filling pump and the air in the tire chamber is forced out of the tire. When liquid foam fill begins to come out of the air escape hole drilled into the tire, the hole is plugged and more foam mixture is pumped into the tire to achieve a required pressure rating. When the right pressure is achieved the valve hole is sealed. The polyurethane foam fill mixture then cures for 24 to 48 hours into a synthetic rubber-like core rendering the tire flat proofed.
Polyurethane foam fills come in different hardness ratings (durometer scale) for different applications where flat proofing is deemed necessary. The various manufacturers of polyurethane foam fills have their own unique formulations to achieve their hardness ratings. With the large variety of equipment types, applications for use, end user site specific conditions and other unique requirements that may be present, choosing the right durometer of foam fill is essential. Basically, there are four ranges of foam fill hardness:
In the last several years with the recognition of Green or environmentally friendly initiatives, manufactures of polyurethane foam products have come out with equipment to reutilize cured foam. For many years, once the tire in a foam filled assembly reached the end of its useful life, the worn-out tire and foam fill would have to be cut off the wheel so a new tire could be mounted and the assembly could then again be foam filled for reuse on equipment. In many cases the foam was disposed of as waste in a landfill.
Some commercial tire dealers would (and some still do) cut up the used foam into smaller chunks and put the chunks back inside of the new tire being remounted on the wheel and then virgin fill is pumped in the tire with the chunks dispersing throughout the foam. This process is known as “chunking”. The pros for chunking is that you need less virgin foam fill to refill the new tire assembly and therefore you save the customer purchasing the new foam filled assembly money. The cons for chunking is that it is the chunks are not consistent or uniform in size and are not dispersed evenly throughout the new foam filled assembly. There is no chemical bond between the chunked foam fill pieces and the new virgin foam fill. Friction between the chunks and the virgin foam fill creates excessive heat which will lead to premature foam fill failure. The chunks can lead to voids in the foam filled assembly and those voids can lead to flat spots forming or premature failure of the foam filled assembly due to the chunks moving inside the foam fill leading it to fracture and break down of the foam inside the tire. The biggest con for doing chunking is that the new foam being pumped into the new assembly IS NOT warranted by the foam manufacturer.
The better solution was arrived at by the polyurethane manufactures with the introduction of re-grind equipment. Re-grinder’s as they are known take previously used foam fill chunks and grind the foam into small pieces. In the new foam fill equipment with re-grind pumps, these small pieces of re-grind foam are blended back in again with virgin liquid foam fill and pumped back into the new tire/wheel assembly. The pros for using regrind are many:
The benefits of using foam fills in tires are many and there are a few cons.
Foam filled tires features
Pro’s – A flat proof tire!. Tires can be punctured, cut and chipped and the tire will not go flat and the equipment will continue to roll and do its work. Works in any tubeless or tube type tire with a sound casing. Will work in extremely adverse weather conditions even down to 70 degrees below zero Fahrenheit. Excellent heat dissipation qualities to reduce heat buildup.
No chance of a tire blow out causing instantaneous flats. Protects your operators, other workers or pedestrians in the work area from the explosive force of a blown-out tire.
Limited chance of equipment tip-overs due to operators losing control of equipment to due to instantaneous tire failure.
Increased weight and tire ballast in overload or applications were ballast is required or beneficial.
Limp-in capability. Severe tire damage won’t stop the equipment from moving to a safe stop location out of the work area.
Greater productivity due to elimination of equipment down time due flat or leaking tires.
Eliminate or greatly lower your tire repair costs. Flats and down time are expensive.
Retreading is possible to extend the service life of the foam filled mounted tire/wheel assembly (qualified retreader’s are necessary).
Improved tire life due to tires maintaining proper inflation and deflection on the work surface.
Reduction in lost wages and income due to equipment down time.
Typically, the cost of the foam fill will pay for itself the first time you need it. Except you may never know it until you stop the equipment to find your tires has a puncturing object stuck in it or the tires has been damaged such that a pneumatic assembly would have left you sitting idle.
Multiple ranges of foam fill hardness can be pumped into a nearly limitless variety of tires used in a very broad range of equipment applications. Remember no two applications are identical.
Polyurethane foam components Part A and Part B are composed of petroleum based chemicals and are subject to the price fluctuations of crude oil.
They add significant weight to the mounted tire/wheel assembly. A draw back if weight is an operational consideration. A benefit when increased ballast is desirable. Depending on the user or equipment owner, that weight may not be considered a disadvantage. They have to make the call.
A vast range of pneumatic tires are capable of being foam filled for use in an extensive list of applications.
Agricultural equipment and implements
Push back tractors
Tractors (Front and rear)
Ramp maintenance equipment
Trash removal equipment
Tree service equipment
Lumber yard equipment
Material handling equipment
Road building equipment
Sand and gravel equipment
Sewer working equipment
Skid Steer loaders
Golf Course Maintenance
Sod farming equipment
Surface and Underground Mining equipment such as:
Front end loaders
Other General Applications suitable for foam filling:
Golf Ball Retrievers
Rural Mail Trucks
Carts / Wagons
Ice Grooming Equipment
Compact Utility Loaders
Another approach to running pneumatic tires without air is using Trojan Tire, tire liners. Trojans tire liners are made from custom cut sheets of cellular rubber. These custom cut liners are cut to fit tires by tire size. The liners are installed into a tire one layer at a time. Once all the layers are installed inside the tire, the tire and liners are pressed onto the multi-piece wheel. One pressed on, the removable side flange is pressed down onto the tire and the lock ring is installed. The wheel is then ready to be installed on the machine. It is airless so it will not go flat.
These tires are completely flat proof, puncture proof and cut resistant. There are specialized applications it is suitable for, size limitations, load and speed limitations and heat buildup issues. They are air-less tires so there is no air pressure to contend with. You have to be an authorized dealer to sell or you have to buy from one.
Trojan Tire makes two kinds of liners. One is the “Reusable Heavy Duty Soft Core”® and the other is the called Tuffil® which is mostly for a one use installation.
The only way to get Trojan Tire liners is to buy them direct or from one of their authorized tire dealers. They want to make sure the product is used correctly in whatever application you have in mind.
Cellular rubber is different from hard rubber because it is created using gas developing agents which introduce air, thus making the material less hard and dense but more heat resistant and absorbent. Cellular rubber, in comparison to solid rubber has less density.
The two main varieties of “cellular” rubber are:
Open cell or sponge rubber has air cells that are open and interconnected to the neighboring cells. This pattern allows air and moisture to seep in easily, giving this rubber its absorbent quality and the ability to regain its physical form after compression.
Closed cell or expanded rubber which doesn’t allow the seepage of fluids. This rubber is cheaper and has the ability to stay afloat in water which can’t violate its structure.
Cellular rubber is a modern miracle and can be defined in terms of other specifications like ability to absorb shock, floatation capacity and fluid immersion. Cellular rubbers range consists of a large number of qualities with many different properties. Cellular rubber is black foamed rubber material with closed cells.
Air-Like Ride: Air-Cell Rubber is Shock Absorbing to Operator and Machine. This means happier and safer operators and Reduced Maintenance Costs.
Strong for Long Tread Life: Manufactured from real cellular rubber that is much stronger than polyurethane. This means longer tire life because will not easily breakdown under higher loads and speeds – leading to premature tire failure.
Best for the Environment:
One additional benefit is they provide better protection against tire sidewall cuts than does polyurethane foam fill. In the event of a large tire sidewall cut where the foam fill is exposed, foam fill does not have the density to hold together. Over time with continuous movement the foam fill will break down and you will not have the benefits of a foam filled tire. Trojan Tire liner will continue to work because of their design. Not ideally of course, but at least you can get your machine to a service area to get the tire changed.
You will find Trojan Tire liners in use at many of North America’s leading Underground Coal Mining Companies in their fleets of scoops, battery haulers, shuttle cars and support equipment. Trojan’s patented liners help to increase the tire’s load capacity by up to 50% over air, which is an ideal feature to help these specialized machines in these harsh environments to achieve their production targets in a safe and sound manner.
Coal miners are serviced via Trojan’s Dealer Network. Trojan dealers receive extensive service training and sales support on how to best market and apply the Trojan products for best results and lowest costs.
Coal machine Original Equipment Manufacturers fit their machines with Trojan Tire liners at the factory level. Trojan offers unique solutions to OEM’s and the aftermarket as well as technical advice to help you select the best tire options for your operation.
Trojan Soft Cores are widely accepted as the best fill medium for radial tires to get the maximum performance and longevity out of a radial tire. Higher quality bias ply tires get an air like ride with Trojan’s soft riding real cellular rubber compounds.
Using Trojan’s tire liner technology to replace the air inside a tire eliminates any explosive force potential you could possibly experience with pressurized air. Trojan Tire liners are promoted “ideally for confined space underground mine applications – giving your operators a more healthy and safe work place and yielding higher performance. Implementing safety programs help to reduce management liability exposure.”
Trojan Air-Cell Technology helps your tires to have an increased load capacity, in the range of 25% to 50% depending on bias or radial construction.
Trojan Tire liners are only made to fit certain sized tires. They have a pretty large range of common sizes available. If you have questions about tire liners to fit the tires you want to flat proof you need to contact Trojan Tire or one of their approved dealers for more information.
Trojan Tire Inc. is the Manufacturer of Patented Trojan Air-Cell® Rubber Tire Fill Technology.
Solid rubber tires come in two main types. The press on variety and the molded-on variety. One more kind of solid tire we will look at is the semi-pneumatic tire. Another offering that has been around for over 20 years is the “segmented tire”.
Solid rubber tires are also referred to as “cushion tires”. Solid rubber tires are completely flat proof, puncture resistant and cut resistant. There are however some size limitations, issues with loads and speeds and heat buildup. Since rubber is so dense, these types of tires can also be very heavy. So depending on the application involved, that weight can be an advantage or a disadvantage.
Solid rubber tires are also very expensive compared to pneumatic tires since rubber is not cheap. But when it comes to a cost of ownership, the cost comes down because they will last 4 to 8 times longer than a comparable foam filled tire.
Solid rubber tires offer many benefits because they are completely flat proof, puncture proof, cut proof and snag proof. They work very well in many extreme and abusive applications, but not well at all in others. Solid rubber tires have little shock absorption like you will find in pneumatic tires. In applications where machines and operators are maneuvering over uneven ground or rolling over obstacles at more than creep speeds, the machine and operator will be subjected to a lot of shock and vibration. Solid tires have very little give. Manufacturers of solid rubber tires have invented tires with “aperture’s” molded into the tire side walls to give the tires some “give” or cushioning. Each manufacturer has their own benefits as to why their aperture design is better. These aperture designs can come in a single ring of holes to multiple rings of holes spaced in different patterns around the tire. Manufactures have some up with different sizes of holes, oval holes and triangular holes. Each with their own performance benefits.
Long term use and exposure to all the extra shock and vibration resulting from using solid rubber tires on a machine can lead to additional and unexpected equipment maintenance. There is also the issue of “whole body vibration” which over time can cause health issues for operators of heavy equipment equipped with solid rubber tires.
In applications where the working surface is smooth and hard, solid rubber tires on a machine will work very well. Applications such as solid waste management where the machines will be operating on concrete or asphalt surfaces. They also are work very well on machines that go slow and lift very heavy weights like transfer trailers that move heavy materials from place to place. One example is on certain kinds of underground mining equipment. You will also find them in junk yard and scrap yard applications on equipment that is mostly stationary but must be moved on occasion like Sennebogen material handling machines. You will also find them in demolition, road building and construction applications.
Pressed on solid rubber tires come in two varieties as well.
You will find “pneumatic shaped tires” made to fit standard wheel or rim profiles and sizes. But you will need a tire press to push these tires onto the wheel. Not all tire shops have access to these tire presses.
You will also find solid rubber tires that are molded onto a steel band. Those solid tire tires are then pressed onto custom wheels that are then mounted onto the vehicle. These are commonly found on many kinds of forklifts.
There are also special wheels that have solid molded rubber on them. These are found on a several kinds of industrial equipment as well as aerial work platform scissor lifts.
There are now several companies that are making pneumatic shaped tires that are pressed on conventional wheel and rim sizes. These companies are now offering swap out programs for owners of large heavy equipment. All you need to do is call them up, tell them what machine you have and they will ship you a solid rubber tire mounted on a wheel assembly that is ready to be mounted on your machine. The owner of the machine just changes out the air-filled assemblies on their machine and replaces them with the new solid tire assemblies. The air-filled assemblies are then shipped back the company that supplied the solid tire assemblies so they can be used in their swap program for solid tires.
Manufacturers of the press on tires use different types of tire core constructions as well as aperture designs to give the tires a more cushioned performance characteristic.
Molded on rubber tires are available for a wide range of heavy equipment from forklifts, wheel loaders, rubber tired dozers, yard cranes and a whole host of other industrial equipment. These molded-on rubber tires and molded to custom sized wheels and the rubber is applied in varying thickness specified by the customer. One the rubber is molded to the wheel and then vulcanized in an autoclave, customized tread designs can be cut into the tread face or they can be left as a smooth tire. When being purchased for large equipment like wheel loaders you will be removing the existing tires and wheels and must buy custom built wheels made just for molded solid rubber tires. Not always in inexpensive proposition.
These tires can be manufactured with special formulations of rubber in layers that produce tires with special qualities to offer outstanding cut, chip and wear resistance. Then can be molded in a wide range of widths for custom wheel sizes.
Manufacturers capable of making molded on solid tires can custom build special tire/wheel combinations. All you have to do is ask if you have some special need.
Molded on rubber tires can be recapped as well. Then the rubber has been worn down or severely damaged the wheel/tire can be taken out of service and sent back to the factory to be rebuilt.
There are many companies around the world that make solid rubber tires so finding them is not difficult.
Semi-pneumatic tires are solid rubber tires but they are hollow in the middle. They are designed to operate without air. They are made with very thick sidewalls and tread face. They must be pressed on a special wheel and then can be used on a machine. The most common application for these tires is for lawn moving equipment. You will find them in use on several zero turn mowers on the from tire positions in front of the mower deck.
Segmented tires are a special application of tire. These are special wheels with segments of tire tread that are bolted to the outer surface of the wheel. These tires and wheel are still in use and can be purchased from SolidBoss. These tire/wheels and segments are available in non-marking gray rubber and regular black rubber.
The main benefit of these tires and wheels is as the sections of the tire are worn down or damaged enough that they need to be replaced, the bad segment can be unbolted and replaced. Common applications where you may see these tire/wheel designs in service are aerial work platforms and boom lifts.
Polyurethane tires are found in two types. The press on and the mold on type.
These tires are completely flat proof, puncture proof and cut resistant. There are specialized applications they are suitable for, size limitations, load and speed limitations and heat buildup issues. They are air-less tires so there is no air pressure to contend with.
The forklift and indoors material handling industry is very dependent on polyurethane or “poly” tires and wheels. Poly tires have been widely used for over 50 years now. Poly formulations have a range of strengths and weakness unique their chemical makeup. Polyurethane has a much greater load carrying capability than do rubber tires. Typically, that load carrying capacity of a poly tire is twice that of a rubber tire. Poly is mostly relegated to applications that are indoors and where the machine that uses them operates on smooth concrete.
Polyurethane has a very low rolling resistance compared to rubber. Poly tires are ideal for applications like electric lift trucks or fork trucks.
Polyurethane is much harder than rubber so these types of tires and wheels have little to no cushioning. You won’t see many machines operating outdoors on polyurethane tires because of the lack of shock absorption.
Since polyurethane is so hard it doesn’t have much traction ability to grip the surface it is operating on. The surface should be clean and dry for optimal performance.
Poly tires have a very high wear and abrasion resistance. Typically, a poly tire will outlast a rubber tire by about four times. They also have very high cutting and tearing resistance. They also will not mark floors like rubber tires will.
Polyurethane tires and not well suited for continuous high speed operations since they don’t dissipate heat very well. Will rubber on the other hand dissipates heat very well.
One advantage that poly tires have over rubber chemical resistance. Rubber tires exposed to certain kinds of solvents will break down or wear much faster. There are certain kinds of very harsh solvents that will destroy polyurethanes as well.
Press on polyurethane tires and steel bands where the poly material has been molded to the band. These bands come in a wide range of sizes, poly durometers, colors, tread designs, poly depths, widths, diameters and are ready to be pressed onto the machine wheel as required.
Molded on polyurethane wheels are custom made wheels with the polyurethane molded to them. Typically, you see a manufacturer of piece specialized equipment have a custom-made wheel that needs the specific design, be it a proprietary nature or some other engineering requirement, and you must buy that wheel only. There are some poly wheel manufacturers that make a wide range of standard wheel designs that are used across industry. You may have to do some digging to find what you need.
The Tweel is completely flat proof, puncture proof and cut resistant. There are specialized applications that it is suitable for, size limitations, load and speed limitations. They are air-less tires so there is no air pressure to contend with.
Michelin’s engineers in 2005 came out with their invention called the Tweel. Tweel is short for a tire and a wheel. It won several design awards after its introduction. The unique design of the Tweel also got other companies busy creating designs to compete with the Tweel. We will look at some of those under Variants. Click here to read a more detailed explanation of the Tweel.
Benefits of the Tweel design are that it is airless, can be made with multiple tread design features, is recapable, is very useful in applications for vehicles like mowing equipment that don’t have shock absorbing suspension systems.
Since the introduction of the Tweel other variations on the idea have come to market. They are mostly niche specific products designed to certain applications.
Let’s look a couple.
The Non-Pneumatic Tire (NPT) by Resilient Technologies. Click here for more information and to see videos of the NPT in action.
The NPT was developed for the U.S. Army to use on High Mobility Multipurpose Wheeled Vehicle (HMMWV or Humvee). They are airless tire and wheel assemblies that can’t get shot out by a bullet or shrapnel for a road side bomb.
Non-Pneumatic, Non-Solid Wheel
Big Tyre in Australia is developing non-pneumatic, non-solid wheels for underground heavy equipment in association with, and significant financial support from, the Australia Coal Association Research Projects (ACARP). Click here for more information on the unique wheel design.
Bridgestone Tire has gotten on the bandwagon too with their version of air free puncture-less tires too. Click here to read more.
The end. At least for today. Wow. We have gone on a journey. There is a lot more that could be said about flat proofing pneumatic tires, puncture resistant tires and solid rubber tires. Check back for more interesting articles and blog postings about off the road tire and wheel products. I have much more coming.
What is a tire? A tire or tyre is a ring-shaped vehicle component that covers the wheel rim to protect it and enable better vehicle performance. Most tires, such as those for automobiles, trucks, all types of working equipment, provide traction between the vehicle and the road while providing a flexible cushion that absorbs shock. So "no", they are not just made from black rubber. Tires and wheels is my main focus, so I spend my days dealing with a wide range of customer inquiries about these products. In most cases, it all starts with knowing the tire size to answer a customer’s question or to solve the tires and rims issue.
OTR (Off-the-Road) tires vary in size and chemical composition depending on the type of tire necessary for a particular job or job site environment. Since my job focus is off-the-road I will mostly limit my discussion to heavy equipment that operates off the road. There are however many other applications that require wheels that are made from non-rubber materials such as polyurethane mold on designs. A tire manufacturer designs their product around the sizes, types and dimensions of products produced by wheel rim manufacturers are currently making. However, there are special applications custom wheels and rim and tire packages need to be created based on an equipment manufacturers unique performance and design requirements.
For now, sticking with rubber tire products, the design and manufacturing of OTR tires by the tire company is an exact science in creating a rugged rubber compound that can take a beating on the job site, i.e. moving huge loads of earth in construction and mining. OTR tire companies employ engineering teams to develop the specialized chemical compounds for their OTR tires. Off road tires and off road wheels fitted for off road vehicles come in many tire sizes. Construction machinery, earthmoving equipment, agricultural machinery and mining equipment all take wheels and tires made in varying sizes, tire diameter, tread patterns, load carrying capacities and tire speed ratings. Off road wheels and tires are an important consideration to any company building machines in the heavy equipment industry. During the machine design process engineers take into consideration the machine performance requirements and come up with a package of wheel and tire packages they consider ideal to make a machine perform most efficiently. Simply put, rims and tires are essential.
The tire manufacturing process takes all the materials that compose a modern pneumatic tire such as synthetic rubber, natural rubber, fabric and wire, along with carbon black and other chemical compounds, and combines them into amazingly high tech tire designs. All tires consist of a tread and a body. The tread provides traction while the body typically provides containment for a quantity of compressed air. Before rubber was developed, the first versions of tires were simply bands of metal that fitted around wooden wheels to prevent wear and tear. Early rubber tires were solid (not pneumatic). Today, the majority of tires are pneumatic inflatable structures, comprising a doughnut-shaped body of cords and wires encased in rubber and generally filled with compressed air to form an inflatable cushion. Pneumatic tires are used on many types of vehicles, including cars, bicycles, motorcycles, buses, trucks, heavy equipment, and aircraft.
The indispensable team - the tire, the air pressure and the wheel.
There are two aspects to how pneumatic tires support the rim of the wheel on which they are mounted. First, tension in the cords pull on the bead uniformly around the wheel, except where it is reduced above the contact patch. Second, the bead transfers that net force to the rim.
Air pressure, via the ply cords, exerts tensile force on the entire bead surrounding the wheel rim on which the tire is mounted, pulling outward in a 360-degree pattern. Thus, the bead must have high tensile strength. With no force applied to the outer tread, the bead is pulled equally in all directions, thus no additional net force is applied to the tire bead and wheel rim. However, when the tread is pushed inward on one side, this releases some pressure on the corresponding sidewall ply pulling on the bead. Yet the sidewall ply on the other side continues to pull the bead in the opposite direction. Thus, the still fully tensioned sidewall ply pulls the tire bead and wheel rim in the direction opposite to the tread displacement and matching the total force applied to push the tread inward. New tires are designed to operate at a range of recommended tire pressure readings. Maintaining proper air pressure is essential to optimal tire performance.
Pneumatic tires are manufactured in more than 450 tire factories around the world. Over one billion tires are manufactured in the tire manufacturing industry annually, making the tire industry a major consumer of natural rubber. Tire production starts with bulk raw materials such as rubber, carbon black, and chemicals and produces numerous specialized components that are assembled and cured. Many kinds of rubber compositions are used. The following information describes the components assembled to make a tire, the various materials used, the manufacturing processes and machinery, and the overall business model.
A tire carcass is composed of several parts: the tread, bead, sidewall, shoulder, and ply.
Image By MagentaGreen (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Tread. The tread is the part of the tire that comes in contact with the road surface. The portion that is in contact with the road at a given instant in time is the contact patch. The tread is a thick rubber, or rubber composite compound formulated to provide an appropriate level of traction that does not wear away too quickly. The tire tread pattern is characterized by the geometrical shape of the grooves, lugs, voids and sipes. Grooves run circumferentially around the tire, and are needed to channel away water. Lugs are that portion of the tread design that contacts the road surface. Voids are spaces between lugs that allow the lugs to flex and evacuate water. Tread patterns feature non-symmetrical (or non-uniform) lug sizes circumferentially to minimize noise levels at discrete frequencies. Sipes are valleys cut across the tire, usually perpendicular to the grooves, which allow the water from the grooves to escape to the sides in an effort to prevent hydroplaning.
Tire treads are often designed to meet specific product marketing positions. High performance tires have small void ratios to provide more rubber in contact with the road for higher traction, but may be compounded with softer rubber that provides better traction, but wears quickly.
Tread lugs provide the contact surface necessary to provide traction. As the tread lug enters the road contact area, or footprint, it is compressed. As it rotates through the footprint it is deformed circumferentially. As it exits the footprint, it recovers to its original shape. During the deformation and recovery cycle the tire exerts variable forces into the vehicle. These forces are described as Force Variation.
Tread voids provide space for the lug to flex and deform as it enters and exits the footprint. Voids also provide channels for rainwater, mud, and snow to be channeled away from the footprint. The void ratio is the void area of the tire divided by the entire tread area. Low void areas have high contact area and therefore higher traction on clean, dry pavement.
The bead is the part of the tire that contacts the rim on the wheel. The bead is typically reinforced with steel wire and compounded of high strength, low flexibility rubber. The bead seats tightly against the two rims on the wheel to ensure that a tubeless tire holds air without leakage. The bead fit is tight to ensure the tire does not shift circumferentially as the wheel rotates. The width of the rim in relationship to the tire is a factor in the handling characteristics of an automobile, truck or type of equipment, because the rim supports the tire's profile.
The tire sidewall is that part of the tire that bridges between the tread and bead. The sidewall is largely rubber but reinforced with fabric or steel cords that provide for tensile strength and flexibility. The sidewall contains air pressure and transmits the torque applied by the drive axle to the tread to create traction but supports little of the weight of the vehicle, as is clear from the total collapse of the tire when punctured. Sidewalls are molded with manufacturer-specific detail, government mandated warning labels, and other consumer information, and sometimes decorative ornamentation, like whitewalls.
The shoulder is that part of the tire at the edge of the tread as it makes transition to the sidewall.
Tires are mounted onto wheels that most often have integral rims on their outer edges to hold the tire. Automotive wheels are typically made from pressed and welded steel, or a composite of lightweight metal alloys, such as aluminum or magnesium. These alloy wheels may be either cast or forged. The mounted tire and wheel assembly is then bolted to the vehicle's hub.
Steel wheels for heavy equipment, earth moving equipment and a variety of construction machines are made from thick sheets of steel plate or from hot formed steel sections produced at steel mills. The steel used is made of special formulations made to give the steel enhanced performance characteristics for use in wheels. Off the road wheels are manufactured in many design profiles, thickness and different manufactures are known to provide special designs promoting niche specific enhancements that also promote their unique brands. Off road rims come in a range of standard sizes and rim profiles. There are also several custom wheels and tires out in the market place as well. Those are usually niche products designed for special use cases.
The beads of the tire are held on the rim, or the "outer edge" of a wheel. These outer edges are shaped to obtain a proper shape on each side, having a radially cylindrical inclined inner wall on which the tire can be mounted. The wheel's rim must be of the proper design and type to hold the bead of the appropriately sized tire. Tires are mounted on the wheel by forcing its beads into the channel formed by the wheel's inner and outer rims.
What constitutes an OTR tire? Tires seem like very simple things, don’t they? Many people assume that a tire is just a basic round piece of rubber that is inflated by a tube. In the retail industry, there are thousands of different variants of tire depending on the manufacturer and the use that it will be put to. Off-the-road tires or, OTR tires, are built to take a massive amount of weight and roll through conditions that would stop most cars dead. They all share 3 common types of construction: bias, belted bias and radial.
Bias – A Bias tire means that it is of cross ply construction. It uses cords that stretch from bead to bead. A bead is a bunch of high tensile steel wire that ties the tire to the rim. The cords are laid in layers at opposing angles of approximately 35 degrees to form a crisscross pattern. The tread is then adhered over that pattern. The primary advantage of a tire with this construction is that it allows for the entire body of the tire to flex. This flexibility allows for a comfortable and smooth ride even on uneven or rough terrain. The down side of bias tires is that they have less traction and control at higher speeds.
Belted Bias – An OTR tire of this type starts out with similar construction to the bias. It will usually have two or more of the crisscross layers that we mentioned before but it then has corded or steel stabilizing belts that are attached underneath the tread. Those belts and crisscross layers are at differing angles similar to the Bias tire listed above. This construction really improves the tires performance when put up against non-belted bias tires. Belted Bias is an improvement on the bias because it retains the comfortable ride but the increased stiffness of the construction lessens the rolling resistance at high speeds.
Radial – A radial tire is in some ways the opposite of a bias tire and in others it is combination of Bias and Belted Bias. Radial utilizes cords that extend from the beads and across the tread but they are at right angles to the centerline of the tread. The cords are parallel to one another and stabilizer belts are put into place beneath the tread. All those things come together to strengthen the tire and provide a longer life for the tire, better control at high speeds and lower rolling resistance as well. The disadvantages are that the ride is much rougher at lower speeds and OTR tires will not see as much of a self-cleaning ability.
Many tires used in industrial and commercial applications are non-pneumatic, and are manufactured from solid rubber and plastic compounds via molding operations. Solid tires include those used for lawn mowers, skateboards, golf carts, scooters, and many types of light industrial vehicles, carts, and trailers. One of the most common applications for solid tires is for material handling equipment (forklifts). Such tires are installed by means of a hydraulic tire press.
Semi-pneumatic tires have a hollow center, but they are not pressurized. They are light-weight, low-cost, puncture proof, and provide cushioning. These tires often come as a complete assembly with the wheel and even integral ball bearings. They are used on lawn mowers, wheelchairs, and wheelbarrows. They can also be rugged, typically used in industrial applications, and are designed to not pull off their rim under use.
Tires that are hollow but are not pressurized have also been designed for automotive use, such as the Tweel (a portmanteau of tire and wheel), which is an experimental tire design being developed at Michelin. The outer casing is rubber as in ordinary radial tires, but the interior has special compressible polyurethane springs to contribute to a comfortable ride. Besides the impossibility of going flat, the tires are intended to combine the comfort offered by higher-profile tires (with tall sidewalls) with the resistance to cornering forces offered by low profile tires. They have not yet been delivered for broad market use
Tires are specified by the vehicle manufacturer with a recommended inflation pressure, which permits safe operation within the specified load rating and vehicle loading. Most tires are stamped with a maximum pressure rating. Tires should not generally be inflated to the pressure on the sidewall; this is the maximum pressure, rather than the recommended pressure
Inflated tires naturally lose pressure over time. Not all tire-to-rim seals, valve-stem-to-rim seals, and valve seals themselves are perfect. Furthermore, tires are not completely impermeable to air, and so lose pressure over time naturally due to diffusion of molecules through the rubber.
The tire contact patch is readily changed by both over-and-under inflation. Over-inflation may increase the wear on the center contact patch, and under-inflation will cause a concave tread, resulting in less center contact, though the overall contact patch will still be larger. Most modern tires will wear evenly at high tire pressures, but will degrade prematurely if underinflated. An increased tire pressure may decrease rolling resistance, and may also result in shorter stopping distances If tire pressure is too low, the tire contact patch is greatly increased. This increases rolling resistance, tire flexing, and friction between the road and tire. Under-inflation can lead to tire overheating, premature tread wear, and tread separation in severe cases.
Tires are specified by the manufacturer with a maximum load rating. Loads exceeding the rating can result in unsafe conditions that can lead to steering instability and even rupture. For a table of load ratings, see tire code.
The tire speed rating denotes the maximum speed at which a tire is designed to be operated. For passenger vehicles, these ratings range from 160 to 300 km/h (99.4 to 186 mph). For a table of speed ratings, see tire code.
Tires (especially in the U.S.) are often given service ratings, mainly used on bus and truck tires. Some ratings are for long haul, and some for stop-start multi-drop type work. Tires designed to run 500 miles (800 km) or more per day carrying heavy loads require special specifications.
The treadwear rating or treadwear grade is how long the tire manufacturers expect the tire to last.
Rolling resistance is the resistance to rolling caused by deformation of the tire in contact with the road surface. As the tire rolls, tread enters the contact area and is deformed flat to conform to the roadway. The energy required to make the deformation depends on the inflation pressure, rotating speed, and numerous physical properties of the tire structure, such as spring force and stiffness. Tire makers seek lower rolling resistance tire constructions to improve fuel economy in cars and especially trucks, where rolling resistance accounts for a high proportion of fuel consumption.
Pneumatic tires also have a much lower rolling resistance than solid tires. Because the internal air pressure acts in all directions, a pneumatic tire can "absorb" bumps in the road as it rolls over them without experiencing a reaction force opposite to the direction of travel, as is the case with a solid (or foam-filled) tire.
Tires for Off-The-Road applications, such as mining, earthmoving and port applications, are required to be specialized and tough and mounted on steel rims. OTR tires are offered in a wide range of designs in both Radial and Diagonal constructions and are popular with machine manufacturers, mining companies and ports. The off the road product portfolio includes tires for the entire spectrum of OTR machines like loaders, graders, bulldozers, rigid dump trucks, articulated dump trucks, straddle carriers, empty container handlers and reach stackers, agricultural equipment, ATV, RTV, UTV machines, earthmover equipment, backhoes, industrial equipment, Lawn, garden, and turf machines, material handlers, military type vehicles, off-road flotation type machines, construction, mining, skid steer, rough terrain telehandlers, Man lifts, telehandler and telescopic lifts. Most importantly off the road tires are engineered to last long and provide efficient service.
OTR tires are manufactured for the world’s largest construction vehicles such as haul trucks, wheel loaders, backhoes, graders, rough terrain forklift, and trenchers. OTR tires are designed as either bias or radial construction. The OTR tire industry is increasing the use of radial tire designs due to the improved performance of radial tire designs. Companies dependent upon OTR tires should walk away from tire products not covered by a warranty that promises a quick response to any malfunction pertaining to their products.
Joedamadman at the English language Wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
OTR Tires and heavy duty tires are classified by the type of vehicles they are used on. For example
Dump Trucks. (TRA Codes E-1, E-2, E-3 and E-4)
Since dump trucks must travel under heavy load at high speeds, over relatively long distances, heavy duty tire for dump trucks must have high heat and wear resistance. Sometimes high resistance to cuts is also necessary.
Scrapers. (TRA Codes E-2, E-3 and E-4)
Scraper tires, of which the wide base type is the most common, should have the same properties as those for dump trucks. Superior flotation and traction are also occasionally required.
Front-End Loaders. (TRA Codes L-2, L-3, L-4, L-5, L-4S and L-5S)
Since front-end loaders operate on rough ground, cut and wear resistance are vital and the tires must provide stability for the loader body. Flotation and traction properties may also be necessary, depending on the working conditions. In certain cases, such as the wet and rough conditions of underground mines, the L-4S and L-5S with smooth treads are used because of their high wear and cut resistant properties.
Rubber Tire Dozers. (TRA Codes L-2, L-3, L-4 and L-5)
Since a tire dozer is used not only for dozing and leveling, but sometimes for pushing a motor scraper, tires with better traction than loader tires are necessary. Other requirements vary widely depending on job conditions.
Motor Graders. (TRA Codes G-2 and G-3)
The motor grader, which is used for road leveling, clearing and snow removal, needs tires that provide high traction and directional stability. Other characteristics depend on job requirements.
Tire Rollers. (TRA Code C1)
Tire rollers use wide tread tires that uniformly distribute weight because of their primary use in compacting road surfaces.
Straddle Carriers. (Industrial Service)
Straddle carriers are special vehicles that are mainly used at seaport areas to carry ocean-going freight containers. These tires require extra heavy-duty performance, and wear and heat resistance, because straddle carriers operate continuously and turn frequently.
Towing Tractors. (Industrial Service)
Towing tractors are used to move large aircraft. Thus, these tires mainly require extra traction.
The Industrial tire classification is a bit of a catch-all category and includes pneumatic and non-pneumatic tires for specialty industrial and construction equipment such as skid loaders and fork lift trucks.
According to the Tire and Rim Association, Incorporated (TRA), there are three general classifications of tread thickness for off-the-Road tires: regular, deep and extra-deep. Deep and extra-deep are 1.5 and 2.5 times thicker than regular, respectively. The thicker treads have greater cut and wear resistance. The TRA codes are classified as follows:
Extra-Deep Tread: L-5, L-5S Deep Tread: E-4, L-4 and L-4S Regular Tread: E-2, E-3, G-2, G-3, L-2 and L-3
Although thicker treads give greater wear and cut resistance, they also generate and retain more heat. Accordingly, work conditions for tires with thick treads should be thoroughly evaluated to prevent heat separation and other heat-related damage. Deep and extra-deep tread tires have almost the same overall diameter, which is larger than regular tread tires. When replacing regular tread tires with deep or extra-deep tread tires, the larger overall diameters of the thicker tread tires should be taken into consideration.
Tire Specification Code. It is most critical that Off-the-Road tires are properly matched to the job, oem wheels, and road conditions anticipated. Accordingly, Off-the-Road tires are classified by three types: regular tire, cut-resistant tire and heat-resistant tire. The regular type provides general performance for use under standard conditions. Where many obstacles pose cut damage, cut protected types are most suitable. And under good road conditions where higher speeds can be attained, heat-resistant types are recommended.
OTR tire designers utilize state-of-the-art testing, destructive and non destructive testing, to make sure the inner workings of the tire will hold up when pushed to their limits, but also focus on a tread specific to what the customer requires. This testing is vital when a company’s reputation is on the line. For example, there is a rigorous testing process that judges the heat created by OTR tires when in use which gauges exactly how heat is spread throughout the interior of the rubber. This test is important to discover how much pressure the tire can endure. Tire engineers use techniques such as computer modeling, ndt testing, x-ray inspection, and strenuous road testing to ensure OTR tire designs provide the performance required to conquer every environmental condition. Tire construction may appear to be a simple process but it far from that.
OTR tires keep heavy mining and construction equipment moving forward under dangerous conditions coupled with the pressure of meeting mining and construction production timelines. The thorough computer modeling and testing conducted by tire engineering teams improve the life span of OTR tires by developing better tire designs. Better designs mean less downtime from tire failures and cost savings to the customer.
These categories only represent the basic construction of OTR tires. There are many more OTR tire varieties available that are designed for special environments and conditions. Such as tires for equipment used in:
Agricultural, ATV, RTV, UTV’s, road graders, heavy equipment, earthmover, backhoes, industrial equipment of all sorts, lawn, garden, and turf equipment, wheel loader, material handling, military type equipment, off-the-road earthmoving, construction and mining equipment, skid steers, rough terrain telehandlers, man lifts, and telehandlers.