What You Need to Know When Buying Your Next Set of RimsPosted in How To: Wheels Tires on November 11, 2016
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.
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.
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.
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 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.
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.
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.
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 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.