The Alloy Wheel Fitment, Tyre Stretch, Rolling Radius & Speedo Error Calculator

Insert your existing alloy wheel and tyre specs, and the desired size. The outcome is shown on the diagram.

Your existing setup

Existing Tyre
Existing Wheel

Your new setup

New Tyre
New Wheel
Your Results

Existing

New

Diameter
631.4mm
682.2mm
Circumference
1983.6mm
2143.2mm
Poke
95.6mm
109mm
Inset
107.6mm
145mm
Speedo error
0%
-7.45%
Reading at 30mph
30mph
27.77mph
Reading at 60mph
60mph
55.53mph
Ride height gain
0mm
25.4mm
Arch gap loss
0mm
25.4mm
Wheel Fitment Guide

Compared to your existing wheel, this new wheel will have an inner rim which is 37.4mm closer to the suspension strut. The outer rim will poke out 13.4mm more than before.

The strut shown in the diagram is for show only. Don't worry if the wheel looks like it fouls!

Bear in mind most tyre manufacturers vary slighty from the specs, and that it could be dangerous to run tyres on wheels they aren't designed to fit.

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18x10 ET18 (+-5mm) wheels
WORK Wheels
SSR Wheels
JR Wheels
Rotiform Wheels
Rota Wheels
Concaver
Motegi
Fuel Wheels
Bola Wheels
3SDM
7Twenty
2Forge Wheels
1Form
Niche
Autostar
Dare

Will They Fit - The No.1 Online Alloy Wheel & Tyre Fitment Calculator

Use our comprehensive online wheel size calculator to visualise different alloy wheels and tyre combinations. Calculate your offset, compare tyre stretch, rolling radius and more. Compare your new and existing setup and our tool will show you key measurements for accurate wheel and tyre fitment.

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