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What You Need to Know When Buying Your Next Set of Rims

Posted in How To: Wheels Tires on November 11, 2016 Comment (0)
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When you buy a new set of wheels for your rig, the most important factor is looks. That’s OK. Aesthetics are important to everyone, and they are an important factor when you buy wheels, but they shouldn’t be the only factor. Width, load rating, and offset are just a few of the other things you should consider when shopping for your next set of rims. To understand why these are important, we first must understand what they mean and how they apply to your 4x4.

Larger-diameter wheels provide room for larger brakes and result in more precise handling due to a shorter sidewall, but the tradeoff is that shorter sidewall means the tire cannot conform to the terrain as well off-road when it is aired down.

Diameter
Large-diameter wheels are the trend right now, but both the wheels and the tires are more expensive than smaller-diameter offerings. Currently, 17-inch-diameter wheels have the most wheel and tire options and will fit over most brake packages. We typically like the wheel diameter to be less than half the overall tire diameter. For example, a 17-inch wheel would be the max for a 35-inch tire.

There is a trend on the street to stretch tires onto wheels that are wider than the tire itself. Please do not do this. It may be hella flush, but it would cost less to just put a giant banner on your windshield that says, “I Don’t Go Off-Road.”

Width
Tire manufacturers list a range of recommended wheel widths for each specific tire. They typically recommend a wheel that is 2-3 inches narrower than the tire. We like to run as narrow a wheel as recommended since this helps to keep the tire on the wheel at low air pressure. The tradeoff is that too narrow a wheel can cause the tire to crown, leading to accelerated wear in the center of the tread.

Negative-offset wheels are popular on rockcrawlers with big tires and narrow axles to keep the tires from hitting the frame or suspension components with the steering turned. Wheels with less offset don’t scrub as much when turning though, resulting in easier steering effort and less strain on axle components.

Offset
Offset refers to the wheel’s mounting surface relative to the centerline of the wheel. So a zero offset places half the wheel on each side of the mounting surface. Positive offset results in a narrower track width, with the mounting surface closer to the outside of the wheel. The opposite is true for negative-offset wheels.

Backspacing is critical for many IFS trucks, particularly after they have been lifted. Larger suspension components may require less backspacing, but too little backspacing can lead to tires rubbing the fenders when they are turned.

Backspacing
Backspacing is similar to offset, but unlike offset, backspacing is dependent on the width of the wheel. Backspacing is the distance from the inside lip of the wheel to the mounting surface. Shallow backspacing is equivalent to negative offset, while deep backspacing is equivalent to positive offset.

Most wheels are available in a variety of bolt patterns to fit different applications. In general, 1-ton trucks use eight-lug axles; Jeeps, 1/2-ton Fords, and most 1/2-ton Dodge use five-lug axles; and Toyotas, 1/2-ton Chevy, and 1/2-ton Dodge Dakotas use six-lug axles. Make sure to double-check your bolt pattern before purchasing wheels.

Bolt Pattern
The bolt pattern of your wheels needs to match your axles, although in some situations adapters are available to convert the bolt pattern. Most Jeeps use five-lug wheels, with current JKs being a 5-on-5 bolt pattern and earlier TJs and XJs being 5-on-4 1/2. The first number is the number of lugs, and the second number is the diameter in inches of the bolt circle.

Load Rating
Tires aren’t the only things load rated; wheels are as well. Load rating is a function of the wheel construction and bolt pattern. Steel wheels are often rated at lower loads than cast aluminum wheels, while forged wheels offer the highest load rating. Regardless of the type of construction, a wheel with more lug nuts and a larger bolt circle (such as 8-on-6 1/2 instead of 5-on-4 1/2) will offer a higher load rating due to the distribution of the load.

Center Bore
This refers to the hole in the middle of the wheel. The larger the bolt pattern circle is, the bigger the center bore can be, which is important when fitting over locking hubs and full-floating axles. On hub-centric wheels, the center bore is critical to position the wheel on the axle, unlike lug-centric wheels that use the lug nuts to center the wheel.

The bead of the tire sits in the machined area up against the lip of the wheel. The larger this lip is, the better job it does of keeping the tire on the wheel at low pressure. The tradeoff is that a larger bead seat will make the tire more difficult to mount and dismount.

Bead Seat
The bead seat on the wheel is what keeps the tire bead seated with the help of air pressure. The taller and wider this bead seat is, the lower the air pressure you can run without the tire coming off the wheel. Beadlock wheels add a mechanical clamp with bolts that hold the tire to the wheel (typically only on the outside bead), making it impossible for the tire to unseat even with zero air pressure.

Some beadlock wheels have a flat surface on the wheel, making tire alignment and balance very difficult. Note how these KMC wheels are stepped on both the beadlock ring and the wheel itself to align the tire.
Information regarding the dimensions of your wheels can typically be found on the inside of the wheel. These Method Race Wheels have dimensions on one spoke, load rating on another, and construction information on yet a third.
Proper torque is determined by the size and number of lug studs on your vehicle. For 1/2-inch and 12mm studs, go with 100 lb-ft of torque, while larger 9/16-inch and 14mm studs require 140 lb-ft of torque. Use a torque wrench to tighten, not an impact gun turned up to eleven. Too little and you risk the wheel coming off, but too much torque can stretch the studs and cause them to fail.
Never torque a hot wheel. Wait until the brakes are cool to the touch. Also, new aluminum wheels need to have the lug nuts retorqued after the first 100 miles because the soft metal compresses.
Note how the valve stem in this factory Ford wheel is recessed to protect it. Little details like valve stem placement are important when you’re comparing wheels. We also prefer rubber valve stems to metal ones because they tend to deflect rather than break when subjected to trail use.
Wheels can either register on the hub or the lugs. Wheels that are lug centric will have tapered nuts, while wheels with flat lug nuts are hub centric. We prefer open wheel lugs so we can check the thread engagement with a quick glance while out on the trail.
Some wheels have recessed lugs that require special splined lug nuts and a corresponding thin-wall socket. These wheels offer a great look, but you cannot ensure that the lug nuts are tight with just a glance.

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