Tyre width chart
Every tyre width fits a range of rim widths, not a single one. Fit it too narrow and the sidewall bulges; too wide and the tread is stretched flat.
| Section width | Inches | Narrowest rim | Ideal rim | Widest rim |
|---|---|---|---|---|
| 155 mm | 6.1 in | 4" | 4.5" | 5.5" |
| 165 mm | 6.5 in | 4.5" | 5" | 5.5" |
| 175 mm | 6.9 in | 4.5" | 5" | 6" |
| 185 mm | 7.3 in | 5" | 5.5" | 6.5" |
| 195 mm | 7.7 in | 5" | 6" | 7" |
| 205 mm | 8.1 in | 5.5" | 6" | 7" |
| 215 mm | 8.5 in | 6" | 6.5" | 7.5" |
| 225 mm | 8.9 in | 6" | 6.5" | 8" |
| 235 mm | 9.3 in | 6.5" | 7" | 8" |
| 245 mm | 9.6 in | 6.5" | 7.5" | 8.5" |
| 255 mm | 10.0 in | 7" | 7.5" | 9" |
| 265 mm | 10.4 in | 7" | 8" | 9" |
| 275 mm | 10.8 in | 7.5" | 8" | 9.5" |
| 285 mm | 11.2 in | 7.5" | 8.5" | 10" |
| 295 mm | 11.6 in | 8" | 9" | 10" |
| 305 mm | 12.0 in | 8" | 9" | 10.5" |
This is a working guide, not a standards table. The approved rim range is set per tyre by its manufacturer and printed in their fitment data — check it before buying, especially for run-flats, track tyres and load-rated commercial tyres, which have narrower approved ranges than this guide suggests.
Section width is not tread width
The number on the sidewall — the 205 in 205/55R16 — is the section width: the widest point of the inflated tyre, sidewall bulge included. The tread touching the road is narrower, typically by 15 to 25 mm. This matters for clearance: the part most likely to catch a strut or arch liner is the sidewall bulge, not the tread.
Section width is also quoted at the tyre's reference rim. Mount the same tyre on a wider rim and the real section width grows by roughly 5 mm per half inch of extra rim.
What happens outside the range
On a rim narrower than approved, the sidewalls pinch inward and the tread crowns, so the centre wears faster and turn-in feels vague. On a rim wider than approved, the sidewall is pulled taut, the shoulders take more load, and the tyre is more vulnerable to rim and sidewall damage from potholes.
Related
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.