Wheel Offset Difference Calculator
Compare old and new wheel offset. See how far the wheel moves inward or outward and how much track width changes, in mm and inches.
Compare old and new offsets.
Wheel Offset Difference Calculator: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Wheel Offset Difference Calculator Works?
The Wheel Offset Difference Calculator works by subtracting the old offset from the new offset to get the sideways movement of the whole wheel. The tool uses 3 steps.
Enter old offset
Type the current ET, for example ET45.
Enter new offset
Type the new ET, for example ET35.
Read the movement
The calculator returns a 10 mm (0.39 in) outward shift on each wheel and a 20 mm (0.79 in) wider track on the axle, assuming equal wheel widths.
Wheel Offset Difference Calculator Formula
The Wheel Offset Difference Calculator formula is ΔPosition = ET_old − ET_new, where a positive value moves the wheel outward.
Δout = ET_old − ET_newΔTrack = 2 × (ET_old − ET_new)- ET_old, ET_new
- Old and new offset (mm)
- ΔTrack
- Change in axle track width (mm)
Worked example
Moving from ET+25 to ET−12 shifts each wheel 37 mm (1.46 in) outward and widens the axle track by 74 mm (2.91 in), with the same wheel width.
Wheel Offset Difference Calculator Conversion Table
The Wheel Offset Difference Calculator conversion table shows wheel shift and track change for 7 common offset changes.
| Offset change | ΔET | Wheel shift | Inner edge shift | Track change |
|---|---|---|---|---|
| ET+45 → ET+35 | -10 mm | +10 mm (+0.39 in) outward | -10 mm inward | +20 mm |
| ET+45 → ET+40 | -5 mm | +5 mm (+0.20 in) outward | -5 mm inward | +10 mm |
| ET+40 → ET+25 | -15 mm | +15 mm (+0.59 in) outward | -15 mm inward | +30 mm |
| ET+35 → ET+45 | +10 mm | -10 mm (-0.39 in) outward | +10 mm inward | -20 mm |
| ET+18 → ET+0 | -18 mm | +18 mm (+0.71 in) outward | -18 mm inward | +36 mm |
| ET+25 → ET-12 | -37 mm | +37 mm (+1.46 in) outward | -37 mm inward | +74 mm |
| ET+0 → ET-24 | -24 mm | +24 mm (+0.94 in) outward | -24 mm inward | +48 mm |
What is Wheel Offset Difference Calculator?
A Wheel Offset Difference Calculator is a tool that shows how far a wheel moves sideways when the offset changes and the width stays the same. Every millimeter of lower offset moves the wheel 1 mm outward.
Offset changes move the inner and outer edges by the same amount in the same direction. Width changes move the edges in opposite directions.
Large offset reductions raise scrub radius, which adds steering kickback and wheel bearing load.
What are the uses of Wheel Offset Difference Calculator?
There are 4 main uses of the Wheel Offset Difference Calculator, including flush fitment and brake clearance.
Flush fitment
Push wheels outward to the fender line.
Brake clearance
Move a wheel outward to clear a big brake caliper.
Strut clearance
Restore inner gap with a lower offset.
Track width planning
Estimate stability changes from a wider track.
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