Outer Tire Position Calculator

This calculator works by adding half the tire width increase to the outward movement from an offset change. It shows how far the outer sidewall moves toward the fender.

1. Enter the current tire width, for example 265 mm.
2. Enter the new width, for example 315 mm.
3. Enter the offset change, for example −25 mm.
4. Read the outer movement: +50 mm (+1.97 in) outward.

The formula is Outer Move = (New Tire Width − Old Tire Width) ÷ 2 − Offset Change.

Worked example: 275 mm to 295 mm with an 18 mm lower offset gives 10 + 18 = 28 mm (1.10 in) outward.

A lower offset is a negative offset change, and subtracting a negative number adds outward movement.

The conversion table shows outer sidewall movement for 8 tire and offset changes. Movements run from +10 mm (+0.39 in) to +59 mm (+2.32 in).

The largest move comes from a 285 to 315 mm tire on a wheel with 44 mm less offset.

The Outer Tire Position Calculator is a tool that predicts how far the tire's outer sidewall moves toward or past the fender. Outer position controls "poke," the amount the tire sticks out from the body.

Many regions limit how far a tire may extend past the fender. The calculator lets you check the change before fitting.

This calculator has 4 uses: poke planning, fender-flare decisions, legal checks and lock-to-lock checks.

• Plan poke: Hit a target stance.
• Decide on flares: See when flares are needed.
• Check legal limits: Compare with local fender coverage rules.
• Check steering lock: Find fender-liner contact at full turn.