OTR wheels or Off The Road wheels are different from Over The Road wheels.
What does that mean?
Over the road wheels are manufactured to a DOT or ETRTO standard’s and are intended to operate at much higher speeds than off the road wheels (specifically greater than 45 mph). The wheels job is to mount off road tires and then the tire and wheel assembly is mounted on to the vehicle. Over the road wheels are the kind of wheels and tires you find on cars, trucks, semi tractors and trailers and motor cycles. Simple stuff right?
OTR Wheels or off road wheels, the kind used for working machines (not the kind intended for sport or competition vehicles) are typically built from heavier or thicker material such as steel weld wheels, and are intended to mount off the road tires or what some industry professionals referr to as off-highway tires. Off the road (OTR) and off-highway are terms that can be used interchangeably in the industry. Those off the road tires come in a broad range of tread styles and construction types. If you are in the business you already know that. So why explain it?
What most people outside the industry don’t understand about tires and wheels is that there a very large number of rim designs (we call them rim contours or profiles), single-piece or multi-piece rim wheels, that may mount the same OTR tires. There are a few industry standards organizations that provide the guidelines to OE wheels manufacturers of these products so there is some consistency of designs that are available in the marketplace. These rim profiles or contours come in varying widths, material thicknesses and flange heights and widths. Multiple widths of the same rim diameter may be able to mount the same tire. On top of that, you may have a tire size and design that was designed to mount only on a certain kind of rim, but it in fact may be able to be mounted on several other rim profiles as well. Sounds confusing right? Truthfully it can be very confusing to sort out what a customer has on their equipment and what he needs for a replacement or if the customer wants to do a conversion to a new tire and wheel size.
If you want to take a look at what I am describing to you, get your hands on a copy of the latest Tire and Rim Association Handbook and/or product catalogs from the worlds dominate wheel and rim manufacturers. Start looking through these publications and you will quickly understand the broad range of products and designs and how those products are represented for use in a dizzying array of equipment uses.
What my job is about? OEM wheels and aftermarket wheels.
It is my job to figure out what a customer is looking for and give them the right wheel or rim that mounts the tire they want or need to use for their machine and the application (or function of the machine). This is where all that product knowledge and experience I have comes in that I have acquired in my twenty plus years in the industry. Something I say quite often to people when they ask what I do at my job is I say “I chase parts for a living”. That pretty well describes what a wheel salesman does. You have to take what someone has or says they need and find out if we have it in stock. If we don’t have it, who does or who makes it, do they have it in stock, can I get it and how much will it cost. The fact is there are products in the market place where there is no substitute and you have no choice but to buy that specific product. There are usually choices, but sometimes there are not. Sometimes custom wheels and tires are the only solution that will meet the customers needs or desires for their machine or application.
Off the road wheels and rims designs
A. Off the road wheels and rims come in multiple designs and styles. You have:One piece or single-piece rims. That is a formed rim with no removable components like flanges, side rings or lock rings. These tire rims designs come in a vast range of diameters, widths, profiles, material thicknesses and are used an equally enormous range of applications. In the off the road wheel industry the rims we encounter are all roll form manufactured.
B. Two piece multi-piece rims. These are rims that have a removable flange or side ring or lock ring. These are also called split ring rims. These rims are used in truck, trailer, industrial and mining applications. There are multiple companies around the world that make these designs. Problem is they don’t manufacture them all the same way and their removable flanges/lock rings are not interchangeable.
“Rims used with the proper flange/lock ring are quite safe. Used with the wrong flange/lock ring and there is going to be an accident. You have to remember to use the “right” flange/lock ring with rim you are mounting a tire on.”
C. Three piece multi-piece rims. Three piece rims are made with a removable side ring and lock ring. Again these rim styles come in a wide range of profiles, flange heights, material thickness, lock ring and side ring designs, tubeless and tube type configurations. Again these rims are used in a very large range of applications as well. The ranges of diameters these rims are found in are between 10” to 32” and come in widths that vary from 44″ to as little as 5”. Like two piece rims, these designs are made by a wide range of manufacturers around the world and again they are not all made the same. You will see time and time again that a rim design made by one manufacture will mount the tire perfectly, but the removable side ring and lock ring are proprietary and unique to that rim design. Some designs are pretty much made to a standard size by the dominate rim manufacturers so their component parts will interchange properly. The manufacturers will only recommend that flange and lock ring combinations they specifically manufacturer be used on their rims.
A good rule to follow. In the real world where you have to be more practical.
“You have to know what parts will work and what parts won’t. That’s where hands on experience and thorough product knowledge come into play.”
It is critically important to know what you are working with. Again if you use the wrong parts on the wrong rim there is the possibility of an accident. When working with off the road rims and tires the pressures are usually much higher than over the road rims and tires. A common saying in the off the road tire and wheel industry is “there is no such thing as a small accident”.
D. Four piece multi-piece rims. Four piece rims are typically only found in heavy industrial applications. These designs consist of a rim base, usually two removable side flanges, and a special lock ring. They may also have a rim base, a bead seat ring, side flange and a lock ring. They are usually used with high pressure, high ply and high carrying capacity tires. There are number of special rim designs in this class of rims and some are only made by a single manufacture in the entire world.
E. Five piece multi-piece rims. The five piece design consists of a rim base, two side flanges, a bead seat band and a lock ring. These rim designs come in sizes as large as 63” diameter down to 25” diameter. They also come in varying widths, rim profiles and designs made only by certain manufacturers and can come with driver pocket and key arrangements. Side flanges come in varying flange heights intended to mount and seat properly with specific tire sizes. There are many manufacturers around the world that make five piece rims and components. They use a variety of methods to make the rims. Most use preformed mill sections that are cut, welded and machined into the sizes they need. Some manufacturers make their sections from fully machined bands or forgings. There are again, there several different designs produced by manufacturers. The same rules apply in that you have to know what component parts made by the different manufacturers will work with another and which ones won’t. By making specific purchase decisions it is entirely possible you can box your self in and you will only be able to source replacement parts from only one specific manufacturer. So as a buyer you have to make a wise product purchase decision.
F. Seven piece multi-piece rims. Seven piece rims are a recent innovation of rims manufactured with a rim base with two lock ring groves, two lock rings, two bead seat bands and two side flanges. There rims are used in what are called “quick change” or “speed wheel” configurations on the rear drive wheels positions on the largest earthmoving or mining haul trucks.
G. Bolt together wheels. These wheels are made from two rim halves that are bolted together to make a wheel. They come in varying sizes, manufacturing designs and material thicknesses. There are special bolt together wheels made with multiple components that are made to be used in place of simpler wheels for special applications like military machines. Bolt together rims are made by either having the halves stamped out of sheet metal or they can be casted, forged or fully machined. It all depends on the load, speed, application, ingenuity of the engineer that designed the rim and other potential factors.
H. Forged and machined multi-piece rims. These rim designs are made from steel forgings and are precision machined into their final profile. These designs typically are three piece rims and consist of a rim base, bead seat band and a lock ring. They can also come in multiple other configurations with bolt on eternal retaining rings. Many of these designs are used in underground mining or heavy industrial applications where high ply and high pressure tires are used.
I. The Tweel®. The Tweel is a recent innovation by the Michelin tire company. It is an airless tire design that has the major benefit of never going flat. Since there is no air in the tire you can never get a flat tire. The Tweel is an answer to certain application problems, but it has its limitations. A great design for the right application. Like all new innovations, they are a little expensive.
Rim versus a wheel
The variety of rim designs is quite large, but until you put a disc or something in the rim to attach it to a wheel hub or axle, you can’t do much with it. Rims can be made demountable or you can put a disc in them and drill a bolt pattern in them to bolt them up to a hub and axle.
Demountable rims in the off the road industry have a 28 degree bevel mounting surface. We just refer to that as the “28 degree”. These rims are held in place with clamps that are tightened down on studs with nuts. There are rim designs that are made to be non-demountable meaning they don’t have a 28 degree mounting surface and can only be attached to a hub and axle by means of a disc.
When you take a rim and attached a disc to it you’re making a wheel. Formula: Rim + Disc = Wheel. Simple right?
To make an OTR wheel with a disc we add many more variables to the wheel specification. For example:
1. Disc design or profile. Disc can be:
A. The flat plate
- It will have a specific thickness.
- It will be made of a specific material composition or grade.
- It can have a machined mounting surface. We call that facing.
- It will be cut or torched to a specific outside dimension to fit the rim it is intended to fit. In almost all cases it will be finish machined for proper fitment.
- The disc can be of a special scallop design used by various manufacturers. Those scallops have to be cut to a specific dimension to fit the hub they are intended to mount. And then the bolt holes drilled into them have to be properly spaced and of the right diameter.
B. The formed disc. The disc form can be pressed, stamped out, spun or casted.
- It can come in a wide variety of profiles and shapes.
- Depending on the profile it will have a locus or flat surface the hub will attached to, plus it will have to accommodate the required bolt pattern.
- A specific thickness
- Again made of a specific material
- It will be made to a specific outside diameter for the rim it was intended to fit.
2. The disc we use will have a bolt pattern. That bolt pattern consists of:
- A fixed number of bolt holes. Those bolt holes will have a certain bolt hole diameter. Those bolt holes can be drilled straight or chamfered a variety of ways. The holes can be chamfered on both sides of the disc or on one side only. They can have a spherical or conical chamfer. Those chamfers are machined to varying angles, radius, depths and widths for the types of nuts used to attach the wheel to the hub and studs.
- The bolt holes will be drilled on a Bolt Circle. That bolt circle will match up with the hub to which it will be mounted.
- The bolt holes can be drilled or punched out in a pattern where they are equally spaced or in groupings.
- The disc will have a pilot hole or center bore. That pilot hole will have a specific diameter. The pilot hole can have a chamfer as well. That chamfer will have a specific angle and width.
- The disc may or may not need a valve slot depending on where the disc is attached to the rim.
- Disc can be welded to the rim or bolted to the rim through the use of clamps or a mounting flange.
- The disc will be attached to the rim to provide a specific offset. Offsets are critically important to provide proper wheel and tire tracking for the machine, inside clearances and load bearing.
But wait, there’s more!
Depending on the wheel’s use or application it can have a variety of other add-ons to enhance its performance.
OTR Wheels can have:
1. Driver pocket and key arrangements
2. Bounce rings or support bands.
3. Nut guards
4. Valve guards
5. Flange locks
7. A variety of reinforcements
Buy wheels summary
If you have read this far you get the idea that OTR wheels or off the road wheels come in a wide variety of shapes, sizes and configurations. The variations are almost infinite just like the number of potential machines and applications they can be used on. But when it comes to selecting the right OTR wheel you need to know the tire size you want to mount. The selection of tires you can chose from is immense as well. But, by selecting the tire you intend to mount, you remove a whole lot of other wheel and rim possibilities that an off the road wheel specialist like myself has to eliminate to determine what the right wheel is for you.
Guidelines I give to my customers to help me help them more quickly are:
1. What is the machine manufacturer and model?
2. Do you have a part number or print?
3. What is the tire size?
These three questions go a long way to helping me determine what you need. Then I can get into things like:
1. What do you need specifically?
2. How soon do you need it? Want it “now” or do you have some lead time?
3. Do we have it in stock now?
4. Can I buy it off the shelf or do I have to get it made?
5. What material is available to make it?
6. How much will it cost and how long will it take to get?
Purchasing off the road rims and wheels can be simple or it can be complex. It just depends on your need. It really helps to have a qualified off the road wheel specialist to navigate the waters for you to get the right product that meets your need.
So if you need help with your OTR wheels, call the phone number below or at the top of the page or send me an email and I will do what I can to help you out.