We know that one of the first things you buy for your 4x4 are wheels and tires. We support that decision because we love tires and wheels, and wheel and tire companies help support what we do.
Buying tires is easy. Just get the biggest, gnarliest mud tires that will fit on your rig and go! OK, it’s not that simple, but buying tires is a topic for another article. Here we want to talk about wheels. Wheels, just like tires, must fit what you plan to do with them in order to really excel.
Wheels are more complex than you might think. They come in various diameters, widths, bolt patterns, and more. Do you know about wheel backspacing? Safety beads? Center bore? Don’t worry, we’re here to help and teach. At the end of the day all your questions about which parts make a wheel should be answered, and if we don’t answer a question, don’t worry; it’s probably not that important.
Wheel diameter is one of the most basic dimensions you need to know when thinking about wheels (and tires). In the off-road world wheel diameter is generally tied to brake size, and by that we mean which wheels will clear your vehicle’s brakes, above all else. For cars, larger-diameter wheels also make handling crisper because with the same outside diameter tire there is less sidewall to flex with weight changes and side loads applied to the wheel/tire in a turn.
When off-road, larger wheels tend to create more problems than they solve. Off-road vehicles with large-diameter wheels are more prone to tire sidewall damage, wheel rim damage, and tires slipping off a bead when aired down. We prefer 15- to 17-inch wheels for a number of reasons unless you’re running a really large tire. A good rule of thumb is to run the smallest diameter wheel that will clear your brakes.
Also one of the most basic wheel dimensions is width. There are two schools of thought in the off-road world when it comes to wheel width. Both have their merits—and detractions.
The “wider is better” crew says that wider wheels add track width and thus stability. Wider wheels generally allow a tire to be as wide as possible, aiding in flotation in soft sand or mud. Fans of wide wheels also report that wider wheels allow a tire to be less susceptible to falling into a rut or going offline on rocks.
The “narrower is better” crowd believes, among other things, that the tire is less likely to slip off the bead when aired down and wheel rim damage is less likely (because the tire’s bulge helps protect it).
Who’s right? The truth is it boils down to your intended use, style of driving, and experiences. Our personal preference is to run as narrow a wheel as recommended for a given tire width, but honestly it’s nothing more than our preference. Both wide and narrow wheels have benefits and drawbacks and yield a different look to the tire and vehicle.
Bolt pattern is simply the diameter and number of wheel studs on your axles. This generally varies by year, make, and model. Common patterns are 5-on-4 1/2, 5-on-5, 5-on 5 1/2, 6-on-5 1/2, and 8-on-6 1/2. The first number tells how many lug holes, and the second number is the diameter of the circle. For example, a 5-on-5 1/2 bolt pattern means there are five lug holes around a 5 1/2-inch-diameter circle. A rule of thumb is that larger and more wheel stud openings are stronger, but bolt pattern is generally dictated by what axles you are running (and that’s usually dictated by tire size, intended use, weight, and horsepower/torque).
Wheel offset and backspacing are probably two of the more confusing wheel terms you’ll ever run into. They are confusing because they are two different methods of describing the location of the wheel mounting surface relative to the front and back of the wheel (front being toward the curb, and back being toward the differential).
Backspacing is simply the measurement from the wheel mounting surface to the rear edge (rim) of the wheel.
Offset is either a positive value, a neutral value (zero), or a negative value. What it describes is the distance of the wheel mounting surface from the centerline of the wheel. A wheel with zero offset means the wheel mounting surface is directly at the middle of the wheel. A positive number means the wheel mounting surface is closer to the front of the wheel (curb side). A negative offset means the wheel mounting surface is closer to the back of the wheel (differential side).
A wheel with shallow backspacing has negative offset. This makes the track width of the vehicle greater and may provide more clearance for shocks and other axle components, but can be harder on steering parts. A wheel with deep backspacing and positive offset makes a vehicle narrower and is generally easier to steer, but the wheel can interfere with suspension parts. Once again, neither extreme is necessarily good for your 4x4. Our personal preference if given a choice is to run a wider axle with a wheel with deeper backspacing (positive offset).
Wheel Safety Bead
The safety bead, or bead seat, is a raised lip about an inch inside the wheel’s outer edge or rim where the tire sits. The safety bead, in conjunction with air pressure, helps prevent the bead of the tire from slipping inward. If the tire’s bead does slip over the safety bead then all the air will escape from the tire/wheel. If you’re lucky all you have is a flat. If you’re unlucky you have just destroyed your wheel or rolled your 4x4 when the wheel dug into the ground.
One would expect all safety beads to be about the same size and shape, but they are not. Some are larger than others, and some wheels have almost no safety bead to speak of. The worst offenders are going to be wheels designed to be used with inner tubes and, for some reason, 16.5-inch diameter wheels, which seem to lack a decent safety bead.
Outer Rim/Wheel Lip
This is the edge of the wheel either on the front face (curb side) or the back face (differential side) of the wheel. The rim is important because it, along with air pressure and the wheel’s safety bead, holds the tire on the wheel. The wheel rim can be bent or dented off-road, and that’s bad. Generally we look for steel wheels because they can be bent back into shape, or aluminum wheels with a thick outer rim. That allows you to beat them against rocks, logs, and other trail debris without too much worry.
Center Bore/Mounting Style
The hole in the center of the wheel is called the center bore. Gnerally the size and properties of the center bore are determined by the bolt pattern and how the wheel mounts to the hub. Mostly what you will want to know is whether or not the center bore of the wheels you’d like to run will clear your hubs, locking hubs, and or wheel flanges.
Many factory wheels are hub-centric, meaning the wheel indexes on the axle flange or part of the hub. These wheels transmit forces from the tire and wheel to the hub directly and via the lug nuts/wheel studs.
Most aftermarket wheels are lug-centric, meaning the wheel is centered on the hub using the lug nuts alone. This can cause damage to the lug nuts and failure when the wheels and tires take heavy hits. Most aftermarket wheel installers will know whether your 4x4 is an oddity and cannot run lug-centric wheels. We have used and abused lug-centric wheels for decades without any failures, but if it concerns you, know what you need and why. Also, many lug-centric wheels can be made hub-centric with adapter rings.