Wheel Offset Explained: ET, Backspacing and Perfect Fitment
Wheel offset (ET) explained simply: positive vs negative offset, how width and offset work together, poke and tuck, spacers, and how to calculate fitment.
By Ayoub Farid · · 2 min read
Offset is the single most misunderstood wheel spec, and the one that decides whether your new wheels sit perfectly flush, rub on every bump or hide deep inside the arches.
What offset is
Offset is the distance, in millimeters, between the wheel's mounting face (where it bolts to the hub) and the wheel's centerline. It's stamped as ET (e.g. ET35).
- Positive offset: mounting face is toward the outside of the wheel; the wheel sits further in. Most modern cars use positive offset.
- Zero offset: mounting face is exactly at the centerline.
- Negative offset: the wheel sits further out, common on trucks and deep-dish wheels.
Offset and width work together
A wider wheel with the same offset grows equally inward and outward. To keep the inside clear of suspension, you usually need a lower offset when going wider, but that pushes the outside further out.
Rule of thumb: every 10 mm lower offset moves the outer face 10 mm outward. Every half-inch more width (about 12.7 mm) adds about 6.35 mm on each side.
Poke, flush and tuck
| Term | Meaning |
|---|---|
| Tuck | Wheel sits inside the fender |
| Flush | Wheel face lines up with the fender |
| Poke | Wheel sticks out past the fender |
Flush is the look most people want. Poke can be illegal in some places and throws road spray onto the body.
Backspacing
Backspacing is the distance from the mounting face to the inner edge of the wheel. It's another way of describing the same geometry, common in the US truck market.
Spacers
Hub-centric spacers effectively lower offset. Quality spacers with correct bolts are widely used, but cheap ones are a safety risk. Changing track width also affects handling and steering feel.
Fitment checklist
- Know your car's stock width and offset.
- Use a fitment database or community for your generation.
- Check brake and suspension clearance.
- Consider ride height, since lowering changes how much room the tire has; see lowering options.
- Confirm with a wheel shop.
See the look before the math
Offset decides fitment; style decides whether you'll love it. Preview wheel designs and a lowered stance on your own car with CarForge's Add Accessories, then work out the numbers. See aftermarket wheels guide and how to read tire sizes.
Frequently asked questions
What does ET35 mean?
The wheel's mounting face is 35 mm outward from its centerline, which is a positive offset.
Does lower offset push wheels out?
Yes. A lower (or more negative) offset moves the wheel further outward.
Are wheel spacers safe?
Quality hub-centric spacers with proper bolts, installed correctly, are widely used. Cheap or poorly fitted spacers are risky.
How do I know the right offset for my car?
Start from the factory offset and check fitment guides for your exact generation, then confirm with a wheel shop.
Try it on your own car
Identify any car. Redesign yours in seconds.
Snap a photo to get the make, model and specs, or try paint, wraps, wheels, body kits and 16+ AI styles on your own car. On iPhone and iPad.
Download CarForge