Spacer Effective Offset Calculator

This calculator works by subtracting the spacer thickness from the wheel's offset. A spacer pushes the wheel outward, which acts like a lower offset.

1. Enter the wheel offset, for example ET45.
2. Enter the spacer thickness, for example 15 mm.
3. Read the effective offset: ET30.
4. Read the outward movement: 15 mm (0.59 in) per side.

The formula is Effective Offset = Wheel Offset − Spacer Thickness.

Worked example: an ET35 wheel with a 20 mm spacer acts like ET15. The axle track grows 40 mm (1.57 in).

The conversion table shows the effective offset for 6 wheel offsets with 5 spacer thicknesses (5 mm to 25 mm). An ET50 wheel with a 25 mm spacer becomes ET25.

Spacers over 5 mm usually need longer studs or bolt-on adapters. Follow the spacer maker's thread engagement rules.

The Spacer Effective Offset Calculator is a tool that finds the offset a wheel acts like when mounted with a spacer. Spacers are a common low-cost way to change stance or clear brakes and struts.

The calculator turns spacer thickness into an offset value, so you can compare a spacer setup with buying new wheels.

This calculator has 4 uses: stance tuning, strut clearance, brake clearance and wheel-versus-spacer decisions.

• Tune stance: Push wheels to a flush position.
• Clear struts: Move a wide wheel away from the strut.
• Clear brakes: Gain caliper clearance on the spokes.
• Compare options: Weigh a spacer against new wheels.