Understanding Wheel Dimensions

With all of the talk about lift kits lately we sometimes forget that there are new people who are entering the hobby. Those folks have lots of questions and we get asked lots of questions.

One of the more recent questions was about wheel backspacing and offset. They were trying to buy aftermarket wheels that would fit their Jeep after installing a new lift. The lift manufacturer recommended a wheel with 3.75 to 4.5 inches of backspacing and a maximum width of 9 inches to clear all of the suspension and give better control. Before we talk about why that is lets go over what it is.

choosingdiagram

As you can see in the chart backspace is the distance from the mounting surface to the rear edge of the rim. The smaller this number the less rim material is wrapped around the brakes and suspension. It also means the “deeper” the wheel is. Those big wheels that have the lugs and centers sunk in have a very small backspace dimension

wheel-offset-diagram

Wheel offset is where the mounting surface is located in relation to the wheel center line. It adds a somewhat confusing dimension to selecting wheels. We mention it because there are some manufacturers who will notate their measurements using a formula like 16×7 with a 3.5 + 3.5 backspacing. Which in simplest terms means there is a 3.5 inch backspace and zero offset. Offset is really about forces applied. It is best to match your stock vehicles offset to limit the forces applied to the axles, and bearings. If you do that and get a wheel with the proper backspace you will have less chance of vibration and steering issues. You can see in the image above that offset greatly influences where the mounting surface is and how that would place forces differently.

A stock Jeep comes with 17×8 inch wheels, 6 inches of backspace, and a 5 x 5 lug pattern. What what? Yes lug nut pattern and dimensions are important in any discussion about wheels. You can get the backspace correct, the offset correct, choose your perfect rim in the ideal size and not be able to use it. Why? It won’t bolt on to your wheel studs. The Jeep 5×5 means 5 lugs, 5 inches apart. Older Jeeps used a 5×4.5 which means, you guessed it, 5 lugs 4.5 inches apart. If you don’t know your lug nut pattern just check your manual or owners forum.

So here is how we chose wheels for our project JK. The MOPAR 2 inch lift has specifications for wheel dimensions that will fit with no clearance issues and are designed to perform like the OE wheels. No less than 17 inch diameter, 8-9 inches wide, with a backspace ranging from 3.25 to 4.75 inches. What’s nice is it gives you a range to work in and makes it easier to find a wheel that not only looks good but will perform as well.

Take these dimensions and because the world of the internet is so broad you can simply search for wheels that meet these criteria, spend all day looking at photos and order them without leaving your couch. Better yet you can buy them through a vendor like TireRack and have them delivered with tires mounted and balanced with TPMS sensors installed to bolt right on your vehicle!

Hopefully this helps you in your own searches and understanding of buying wheels!

Here is a pic of the finished package we described above.

JK

William Connor

As the Editor, William is responsible for all the good, the bad, the ugly and the indifferent that happens at 4WAAM. William brings a wide range of experience to this role having been a cook, a painter, a machinist, part time mechanic, computer programmer, and writer. He also wields a freely shared opinion on just about everything., just ask him.

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