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Wheel offset (ET) explained

The offset (German: Einpresstiefe, ET) defines where the wheel sits on the hub. It decides whether the wheel sits flush, rubs the strut or sticks out past the fender.

OffsetET +30ET 0ET −30← insideoutside →- - Centre line · ▮ Mounting face
Positive, zero and negative offset

Definition

Offset is the distance in millimetres from the wheel centre line to the mounting face on the hub. If the mounting face is outboard of the centre line, the offset is positive – the norm on modern cars.

  • Higher offset → wheel moves in (towards the strut).
  • Lower offset → wheel moves out (towards the fender), track gets wider.
  • ET 0 → mounting face exactly on the centre line.

Look at offset and width together

The position always depends on width and offset combined. Changes outside and inside are:

Δ outside = (W_new − W_old) / 2 + (ET_old − ET_new)
Δ inside = (W_new − W_old) / 2 − (ET_old − ET_new)
(W = rim width in mm, 1″ = 25.4 mm)

Spacers change the effective offset

Effective offset = ET − spacer thickness

A 10 mm spacer on an ET45 wheel acts like ET35. This makes wheels with too much offset fit – if certificates and clearance allow it.

Try it: enter your values in the calculator and see what changes live.

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General information without warranty – no legal advice. Vehicle documents, certificates and the inspector are authoritative.

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