Backspacing

Wheel backspacing is the distance from the wheel’s hub-mounting surface to the wheel’s inboard edge. It is usually measured in inches and describes how much of the wheel extends toward the suspension.

How backspacing is measured

With the wheel face down, a straightedge is placed across the back rim edge. The distance from the mounting pad to the straightedge is the backspacing. Measurement procedures should be consistent because the wheel’s overall width is normally slightly greater than its advertised bead-seat width.

Backspacing and offset

Backspacing and offset describe related geometry in different ways. Offset measures the mounting surface relative to the wheel centreline, while backspacing measures directly to the inner edge. Wheel width is required when converting between them.

Why backspacing matters

Too much backspacing can move the wheel close to suspension, steering or brake components. Too little can move it outward toward the fender. Tire section width and sidewall shape must also be included in a complete clearance check.

Related terms

Offset, wheel width, fender clearance and brake clearance.