Wheel Backspace

How to Measure a Wheel’s Backspace 

  1. Turn the wheel face (outside) down.
  2. Place a straightedge across the back of the rim as shown.
  3. Measure from the bottom of the straightedge to the center of the wheel (where the wheel is bolted to the brake drum or front hub).

Backspace is important as a measure on its own (too much backspace can lead to a wheel rubbing on suspension pieces or brake lines), but it’s also important as a percentage of the total rim width.  Two rims of the same nominal width but with different backspace dimensions will appear quite different on the car – the one with least backspace will yield the widest track because it will “stick out” further from the car’s centerline.