Innerspace

Most vehicles' backspacing can be measured from the wheel-mounting surface to almost any point at the fender edge or beyond.

Lance Martz
Jul 24, 2002
Photographers: Lance Martz
Since we tuck our rims when our trucks are laid out, this adds an extra variable to the equation. Using these tips, you can correctly measure for the wheel fitment that best suits your suspension setup and lowered attitude of the specific truck. While we were recently at Suspension Dimension in San Bernardino, California, we decided to check out our S-10 to see what wheel fitment would work best with the truck.
Since we hadn't correctly measured for wheels in the past, we've wasted plenty of tires and the backsides of custom wheels. Don't let this happen to you. With enough information, you'll be able to order the right offset wheels for your truck, run shocks more effectively with a 'bagged ride, and have a more driveable vehicle.
Backspacing, Frontspacing & Offset
The relationship between a wheel's mounting pad or surface and the rim itself can be a confusing subject for many truckers. The terms backspacing and frontspacing refer to where the wheel is placed relative to the mounting pad. The terms are not often used together because one measurement will take care of both distances.
If a wheel has a certain measured backspacing, the rest of the distance of the width of the rim is obviously frontspacing. However, backspacing is the most commonly used description of a wheel's spacing. Backspacing is simply the distance from the back of a wheel's mounting pad to the back edge of the rim. Conversely, frontspacing is the distance of the front side of the rim relative to the back of the mounting pad.
Offset is the distance of the mounting pad from the true lateral center of the wheel. A wheel with the mounting pad centered laterally in the wheel hoop has zero offset. When a wheel has its mounting pad closer to the suspension, it has positive offset.
If the mounting pad center is moved out closer to the outside of the vehicle, it has negative offset. Trucks do not typically employ negative offset wheels as frequently as front-wheel-drive cars, and almost all older trucks have positive offset wheels.

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