Wheel Offset (ET) Explained
Offset, stamped ET on almost every wheel, is the single number that most controls how a wheel sits in the arch. Here's what it means, how to read it, and how it turns into poke and clearance.
What is wheel offset?
Wheel offset is the distance, in millimeters, between the wheel's mounting face (where it bolts to the hub) and its true centerline (the middle of the barrel). The mark "ET" comes from the German Einpresstiefe, meaning "insertion depth." A wheel labeled ET45 has its mounting face 45 mm outboard of the centerline.
Positive, zero and negative offset
- Positive offset (e.g. ET45): the mounting face sits toward the outer/front of the wheel, so the wheel tucks further under the car. Most modern front-wheel-drive cars use high positive offset.
- Zero offset (ET0): the mounting face is exactly on the centerline.
- Negative offset (e.g. ET-12): the mounting face sits inboard of the centerline, pushing the wheel outward for an aggressive, "deep-dish" stance.
Lowering the ET number pushes the wheel out; raising it pulls the wheel in. A change of even 10–15 mm is very noticeable.
How offset becomes poke and clearance
Offset on its own doesn't tell you the whole story: you also need the rim width. Together they set how far the wheel sticks out past the hub face (poke) and how far it reaches inboard (inset), which is the room it needs before it touches the strut, spring or control arm:
So a wider rim or a lower ET both increase poke. That's why you can't judge a wheel by offset alone: an 8 inch wheel at ET35 pokes the same as a 9 inch wheel at ET47.
How much offset change is safe?
There's no universal number. It depends on your fender clearance, suspension, tire size and camber. As a rough guide, small changes (under ~5 mm of poke) are usually mild, and large changes risk rubbing the fender (outboard) or the strut/arm (inboard). The only way to know for your car is to compare the exact numbers and check them against your real clearance.