Wheel Backspacing
The offset (aka backspace) is the distance from the inside surface of the dished center (B) to the inside rim lip (A). See diagram below.
For a most 15"×8" wheels this dimension is typically from 1" to 5". The same holds true for 15×10" and 15×12" wheels because the only dimension that changes is the width of the valley.
While it may appear that the offset range should increase with the width of the valley, actually the critical dimension is the distance between the inside rim lip (A) and the inside valley edge (C).
When you're ready to buy a new set of wheels, measure the offset of the wheels that you know work; the ones already on the car.
How To Measure Offset
- Place the wheel (preferably without tire) on a flat surface with the outside up (hub side down).
- Put a ruler down through the center hub hole.
- Note where the bottom side of the center plate strikes the ruler. This is your backspacing/offset.
Page created on 6/29/2004
Last updated on 6/29/2004