Wheel Offset Explained: Picking Wheels for a Lowered Car
By Shane Allen · · 3 min read
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Wheel offset decides where a wheel sits in the arch: tucked in toward the strut or pushed out to the fender. On a lowered car the window is smaller, because the tire also moves up toward the fender lip and the wheel gains negative camber. This guide explains offset in plain numbers, works through three common changes, and shows how to check yours with our free wheel offset calculator.
Offset in one minute
Offset, stamped on the wheel as ET, is the distance in millimeters from the center line of the wheel to the face that bolts to the hub. Higher offset pulls the wheel in. Lower offset pushes it out. Width matters just as much: at the same offset, each extra inch of width adds about 12.7 mm on the inside and 12.7 mm on the outside.
Three worked examples
All three start from an 8 in wide wheel at ET45, a common size on compact and midsize cars. The numbers come from the calculator, which takes overall width as rim width plus 1 in.
| Change | Inside (toward strut) | Outside (toward fender) |
|---|---|---|
| 8 in ET45 to 8.5 in ET45 | 6 mm closer | 6 mm further out |
| 8 in ET45 to 9 in ET35 | 3 mm closer | 23 mm further out |
| 8 in ET45 to 9.5 in ET40 | 14 mm closer | 24 mm further out |
The second change looks small on paper, half an inch wider, but almost all of it ends up on the outside. On a lowered car, 23 mm more poke is usually past the point where the tire clears the fender without rolling it or adding camber.
Why lowering changes what fits
- The fender comes down. At stock height the tire has room to poke a little below the fender lip. Lowered, the lip sits over the tire, so the outside number matters more.
- Camber goes negative. Most cars gain negative camber as they drop, which tucks the top of the tire in. That helps on the outside and costs room on the inside.
- Coilovers can sit closer to the wheel. Many coilover bodies and spring perches are wider than the factory strut, so check the inside number too.
Spacers
A spacer lowers the effective offset by its thickness: a 10 mm spacer on an ET45 wheel works like ET35. Spacers are a cheap way to fix a wheel that sits too far in, but use hub-centric spacers and make sure the studs or bolts still have full thread engagement.
How to check your own setup
- Find the width and offset of your current wheel. They are usually cast or stamped on the back of a spoke, for example 8Jx18 ET45.
- Enter them and the new wheel in the wheel offset calculator.
- If you are lowering the car at the same time, work out the drop with the ride height calculator.
- Plan for an alignment, and for camber and alignment parts if the drop is large.
Shopping for the drop as well? See lowering springs by car or coilovers.
