Tire diameter and backspacing are pure math from a size, a width, and an offset. Type your own numbers below — or start from a factory size out of our fitment guides — and compare two setups side by side.
Tire diameter
Overall diameter of a metric tire size: rim diameter plus two sidewalls. This is the same math behind the computed tire diameters on our build pages.
Tire A: 27.66 in overall diameter
Start from a factory size in our guides
Backspacing & offset
Backspacing is the distance from the wheel's mounting face to its inner lip: (width + 1) ÷ 2, plus the offset converted to inches. The outboard face position is what is left of the wheel's full width.
Wheel A: 6.63 in backspacing · 3.87 in from mounting face to outer lip
This page does math on the numbers you type — nothing here is a fitment recommendation or a guarantee that a tire or wheel will clear your car. Brake clearance, suspension, alignment, and bodywork all matter; confirm any setup on your specific vehicle with a qualified wheel or tire professional. For real-world proof, browse the fitment guides — every figure there is stated by the car's owner.
RIMPICTURES.