Wheel Basics 101: Wheels Specs

So you want to upgrade your wheels and tires but don’t have the slightest idea of what wheel specs you need. Well don’t fear Kami Speed is here to help. While each car is different and requiring their own specs here are the general basics to wheel specs.


So what are the wheel basics?

When purchasing a set of wheels there are 4 specs that you need to look at: diameter (size), width, offset, and PCD, which are usually in the following format.

[Diameter] x [Width] [+/- Offset] [P.C.D.]

i.e. 18 x 10.5 +22 5×114.3

Diameter (size) is just that, the diameter of the wheel. This number is purely preference, but generally speaking the larger your wheel diameter the smaller your tire sidewall. A smaller sidewall means less tire to absorb impacts and generally a less comfortable ride.

Width is how wide you want your wheel to be. Typically speaking the OEM wheel wells leave about 1 inches worth of wiggle room, so if you car comes with a 7-inch wide wheel, you can typically run a 8-inch wheel without much issue (of course depends on other factors).

Offset is the distance from the inside wheel face (where it touches the hub) to an imaginary line at the center of the wheel. This basically means that a positive offset puts more of the wheel into the wheel well, where as a lower or negative offset pushes the wheel further out. This is measured in millimeters. This number is very important, as it ensures your wheels sits in that sweet spot that doesn’t hit the inner suspension or pokes too far out past the fenders. Generally speaking you want to stay around the same offset as your OEM wheels, with big changes requiring more work to fit (more about offset in upcoming articles).


P.C.D. stands for pitch circle diameter which is basically the number of studs and the diameter size circle the studs make. This number does not change so you have to make sure that the wheels you purchase have the same PCD as your vehicle. In some cases you “can” fit slightly different PCD wheels onto your hub, but this requires special lug nuts and is not recommended.