What Is Wheel Offset (ET)? A Complete Engineering Guide

Wheel offset, marked ET on every modern wheel, is the distance in millimetres from the wheel's mounting face — the flat surface that bolts to the hub — to the wheel's true centerline. It is one number, but it controls almost everything about how a wheel sits relative to the suspension and the fender.

Positive offset (the common case on FWD and modern cars) means the mounting face is outboard of the centerline. The hub holds the wheel inward, tucking the tire under the fender. Typical European OEM values sit between ET35 and ET45.

Zero offset means the mounting face is exactly on the centerline. The wheel is symmetric around the hub. You see this on some classic and motorsport wheels where geometry is balanced around the bearing.

Negative offset means the mounting face sits inboard of the centerline. The wheel is pushed outward, gaining track width and stance but losing fender clearance. Trucks, off-road builds and aggressive aftermarket fitments use it.

ET stands for Einpresstiefe, German for 'insertion depth' — a reminder that the value is measured from the bolting surface, not from any decorative edge of the wheel. The number is always stamped on the back of the spoke or barrel by the manufacturer.

Offset is geometry only. It does not describe wheel width, bolt pattern, hub bore or load rating — all of which must also match the vehicle. But once the basic specs fit, offset is the single number that decides whether your stance is OEM, flush or aggressive.

Changing offset shifts the contact patch sideways relative to the steering axis, which alters scrub radius. Small changes are absorbed by suspension geometry; large changes affect steering effort, bump-steer and wheel bearing load. A common rule is to stay within ±5 mm of OEM ET, ±15 mm at most before re-engineering the geometry.

Use the wheel offset calculator to see exactly how a new width and ET combination changes inner clearance, outer poke and total track width versus your current setup. The numbers are deterministic — the only judgement call is how much change your fenders and struts will tolerate in practice.