Wheel Arch Gap Calculator

This calculator works by subtracting the tire's radius increase from the measured static gap between the tire and the fender arch. It shows the space left above the new tire.

1. Measure the current gap from the top of the tread to the fender lip, for example 2.0 in (51 mm).
2. Enter the current size, for example 265/70R17.
3. Enter the new size, for example 285/75R17.
4. Read the remaining gap: 0.89 in (23 mm).

The formula is Remaining Gap = Current Gap − (New Diameter − Old Diameter) ÷ 2.

Worked example: a 1.5 in (38 mm) gap with a tire change from 245/75R16 to 265/75R16 (+0.59 in radius) leaves 0.91 in (23 mm).

The formula covers static ride height only. Suspension compression, steering lock and axle articulation all reduce the gap further.

The conversion table shows the gap left above 8 larger sizes on a vehicle with 265/70R17 tires and a 2.0 in (51 mm) static gap. Remaining gaps run from 1.72 in (44 mm) down to 0.62 in (16 mm).

A static gap under 1 in (25 mm) on a truck with long suspension travel often means rubbing over bumps.

The Wheel Arch Gap Calculator is a tool that predicts the static space between the top of a new tire and the wheel arch. Arch gap, known as fender gap in many shops, is the most visible fitment measurement.

Owners leveling a truck or lowering a car use the figure to plan a look. Owners upsizing tires use it to spot rubbing risks before buying.

This calculator has 4 uses: rubbing prediction, stance planning, lowering checks and leveling-kit planning.

• Predict rubbing: Find sizes that leave too little gap.
• Plan stance: Hit a target gap for appearance.
• Check lowered cars: Combine lowering drop with tire size.
• Plan leveling kits: Match tire size to the new front height.