Spacer Position Change Calculator
Calculate how a wheel spacer changes inner clearance, outer position and track width. Results for 3 mm to 25 mm spacers in mm and inches.
Calculate inward and outward clearance changes.
Spacer Position Change Calculator: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Spacer Position Change Calculator Works?
The Spacer Position Change Calculator works by moving the whole wheel outward by the spacer thickness and reporting the effect at the inner edge, outer edge and axle track. The tool uses 4 steps.
Enter spacer thickness
Type the thickness, for example 15 mm (0.59 in).
Enter measured gaps
Type the current inner gap (8 mm) and outer inset (20 mm).
Apply the shift
The calculator adds 15 mm to the inner gap and subtracts 15 mm from the outer inset.
Read the results
The calculator returns a 23 mm inner gap, a 5 mm outer inset and a 30 mm (1.18 in) wider track with spacers on both sides.
Spacer Position Change Calculator Formula
The Spacer Position Change Calculator formula is Gap_inner,new = Gap_inner + t and Inset_outer,new = Inset_outer − t.
G_in,new = G_in + tG_out,new = G_out − tΔTrack = 2 × tΔscrub ≈ t- t
- Spacer thickness (mm)
- G_in
- Measured inner gap (mm)
- G_out
- Measured outer inset from fender (mm)
Worked example
A 20 mm (0.79 in) spacer pair on a car with an 8 mm inner gap and a 20 mm outer inset gives a 28 mm inner gap, a 0 mm (flush) outer inset and a 40 mm (1.57 in) wider track.
Spacer Position Change Calculator Conversion Table
The Spacer Position Change Calculator conversion table lists inner, outer, track and scrub radius changes for 8 spacer thicknesses.
| Spacer | Inner gap change | Outer inset change | Track change (pair) | Scrub radius change |
|---|---|---|---|---|
| 3 mm (0.12 in) | +3 mm | −3 mm | +6 mm (0.24 in) | +3 mm |
| 5 mm (0.20 in) | +5 mm | −5 mm | +10 mm (0.39 in) | +5 mm |
| 8 mm (0.31 in) | +8 mm | −8 mm | +16 mm (0.63 in) | +8 mm |
| 10 mm (0.39 in) | +10 mm | −10 mm | +20 mm (0.79 in) | +10 mm |
| 12 mm (0.47 in) | +12 mm | −12 mm | +24 mm (0.94 in) | +12 mm |
| 15 mm (0.59 in) | +15 mm | −15 mm | +30 mm (1.18 in) | +15 mm |
| 20 mm (0.79 in) | +20 mm | −20 mm | +40 mm (1.57 in) | +20 mm |
| 25 mm (0.98 in) | +25 mm | −25 mm | +50 mm (1.97 in) | +25 mm |
What is Spacer Position Change Calculator?
A Spacer Position Change Calculator is a tool that predicts how a wheel spacer changes clearance on both sides of the wheel and the vehicle's track width. A spacer adds room on the inner side and removes room on the outer side by the same amount.
The added track width changes handling balance. A spacer pair on the front axle only shifts grip balance toward understeer reduction on many cars.
Scrub radius grows by the spacer thickness, which raises steering effort and bump steer feedback.
What are the uses of Spacer Position Change Calculator?
There are 4 main uses of the Spacer Position Change Calculator, including flush stance and inner rub fixes.
Flush stance
Find the spacer that brings the wheel to the fender line.
Inner rub fixes
Find the spacer that clears a strut or control arm.
Track tuning
Widen one axle to adjust handling balance.
Spare wheel use
Check room for a spacer when fitting a different wheel.
Related Wheel Geometry & Fitment Tools
View All 134 Subtools →Calculate wheel mounting offset.
Compare old and new offsets.
Calculate backspacing using specified wheel dimensions.
Convert mounting measurements.
Calculate outward wheel projection.
Account for spacer thickness.