Wheel Fitment & Clearance Calculator

When to use it

• Compare how a change in existing inner clearance affects remaining inner clearance before committing to parts, setup, or strategy changes.
• Check a workshop, dyno, simulator, or trackside spreadsheet result using a transparent formula: Existing clearance − new inward movement.
• Use the result before changing wheels, tyres, brake hardware, or pressure targets. Track temperature, tyre construction, pad compound, surface grip, aero load, and driver technique can all change the real outcome.

How to use it

1. Enter existing inner clearance in mm; the default value shown is 20 mm.
2. Enter original width in in; the default value shown is 8 in.
3. Enter original offset in mm; the default value shown is 35 mm.
4. Enter new width in in; the default value shown is 9 in.
5. Enter new offset in mm; the default value shown is 30 mm.

How to read the result

Remaining inner clearance is shown in mm. Use the number as a calculated reference point, then compare it with measured data from the car, the part supplier, or the race environment. A mathematically clean answer can still be unsuitable if the inputs are estimated, rounded, measured under different conditions, or outside the normal range for the vehicle.

Assumptions and checks

• The calculator applies the displayed formula directly and assumes the entered existing inner clearance, original width, original offset, new width, and new offset are valid for the vehicle and conditions being considered.
• Changing existing inner clearance and original width together can move the answer in ways that are easy to miss, so make related setup changes deliberately.
• Measure clearances on the actual vehicle because wheel and tyre shapes vary between manufacturers.
• Check brake calculations against pad data, disc radius, hydraulic layout, and balance-bar setup.
• Recheck tyre pressures hot and cold at the circuit rather than relying only on a static estimate.