12mm wheel spacers
A 12mm spacer moves each wheel 12 mm outward, adds 24 mm of track width, and gains 12 mm of clearance between the wheel and the strut.
A spacer is geometrically identical to reducing offset by the same amount. Fitting 12mm spacers to ET45 wheels gives you the exact stance of ET33 wheels.
What changes
| Measurement | Change |
|---|---|
| Wheel position | 12 mm outward |
| Effective offset | Reduced by 12 mm |
| Outer clearance (to the arch) | −12 mm |
| Inner clearance (to strut and spring) | +12 mm |
| Track width | +24 mm |
Where the rim edges end up
Starting from a typical ET45 wheel, with distances measured from the hub face:
| Width | Outer before | Outer after | Inner before | Inner after |
|---|---|---|---|---|
| 6.5J | 37.5 mm | 49.5 mm | 127.5 mm | 115.5 mm |
| 7J | 43.9 mm | 55.9 mm | 133.9 mm | 121.9 mm |
| 7.5J | 50.3 mm | 62.3 mm | 140.3 mm | 128.3 mm |
| 8J | 56.6 mm | 68.6 mm | 146.6 mm | 134.6 mm |
| 8.5J | 62.9 mm | 74.9 mm | 152.9 mm | 140.9 mm |
| 9J | 69.3 mm | 81.3 mm | 159.3 mm | 147.3 mm |
| 9.5J | 75.6 mm | 87.6 mm | 165.6 mm | 153.6 mm |
| 10J | 82.0 mm | 94.0 mm | 172.0 mm | 160.0 mm |
Hardware
At this thickness many cars need longer bolts or extended studs. Check thread engagement before fitting — a spacer that leaves the original bolts short is genuinely dangerous.
Spacers also need to be hub-centric: the spacer must locate on the car's hub, and the wheel must then locate on the spacer's own lip. A spacer that is merely bolt-centric leaves the wheel hanging on the bolts, which causes vibration and fatigues the studs.
Spacers change scrub radius and increase the bending load on wheel bearings, and thicker spacers do this more. This is a real mechanical change, not a cosmetic one. If you are unsure about thread engagement or hub centring, have it checked by someone who can inspect it properly.
Other thicknesses
Work out the exact effect for your setup with the wheel spacer calculator or the full fitment calculator.
How are these fitment figures calculated?
Fitment North calculates declared wheel and tyre geometry from the dimensions shown on the page, using the same tested method as the wheel-offset and tyre-size calculator. Tyre diameter uses rim diameter plus two calculated sidewalls; offset comparisons split width changes across inner and outer edges before applying the offset difference. Results are measurement aids, not vehicle approval. Confirm ratings, clearances and manufacturer guidance before fitting parts.