Wheel Offset & ET Explained for UK Builders

Wheel Offset & ET Explained

Buy the wrong wheels and they’ll either sit tucked inside the arches or rub on every corner. Understanding offset is what separates a flush build from a botched one.

What is ET?

ET (Einpresstiefe, “insertion depth”) is the offset in millimetres — the distance from the wheel’s centre line to the mounting face. ET35 means the mounting face is 35mm outboard of the centre line.

• Higher ET (e.g. ET45) = wheel sits further in (tucked).
• Lower ET (e.g. ET20) = wheel sits further out (flush/poked).

PCD and centre bore

• PCD (pitch circle diameter) is the bolt pattern — e.g. 5x112 for most VAG cars, 4x100 for many Hondas.
• Centre bore must match the hub, or you need spigot rings. Never rely on the bolts to centre the wheel.

The UK practical bit

• Wheels must not protrude beyond the bodywork — that’s an MOT fail and a police matter.
• If you go wider and lower the offset, check for arch rub on full lock and over bumps. Arch rolling or a mild pull may be needed.
• Always get a fresh alignment after changing wheels — tie rod and camber geometry shift with ride height.

Log the spec

Log the wheel brand, size, ET and tyre size on MODLOG so your fitment — and your spend — is part of the build record.