The chart: approved tire width per rim width
Every tire has an approved rim-width range set by the manufacturer. Mount outside it and you risk bead issues, sloppy handling, or a tire shop refusing the job. This chart covers the standard approved ranges — the ideal column is the sweet spot for street use:
| Rim width | Approved tire widths | Ideal street pick |
|---|---|---|
| 7.0" | 195 – 225 | 205 / 215 |
| 7.5" | 205 – 235 | 215 / 225 |
| 8.0" | 215 – 245 | 225 / 235 |
| 8.5" | 225 – 255 | 235 / 245 |
| 9.0" | 235 – 265 | 245 / 255 |
| 9.5" | 245 – 275 | 255 / 265 |
| 10.0" | 255 – 285 | 265 / 275 |
| 10.5" | 265 – 295 | 275 / 285 |
| 11.0" | 285 – 315 | 295 / 305 |
| 11.5" | 295 – 325 | 305 / 315 |
| 12.0" | 305 – 335 | 315 / 325 |
Standard industry approved ranges. Always cross-check the specific tire maker's spec sheet — some performance tires run wide or narrow for their size.
How to read a tire sidewall
In 225/45R17, 225 is the tread width in millimeters, 45 is the sidewall height as a percentage of that width, R means radial construction, and 17 is the rim diameter in inches. Diameter is (225 × 0.45 × 2 ÷ 25.4) + 17 — about 25 inches. Keep any new size within 3% of stock so your speedometer stays honest.
245/40R18 93Y breaks down like this: 245 = tread width in mm. 40 = aspect ratio — sidewall height as a percentage of width (40% of 245 = 98mm). R = radial construction. 18 = wheel diameter in inches. 93 = load index (how much weight each tire carries). Y = speed rating. When you change sizes, the goal is keeping the overall diameter close to stock — check it with our tire size calculator.
Stretch vs bulge: the honest tradeoffs
Stretched (narrow tire on a wide rim): the look the stance scene loves. Tradeoffs are real — less rim protection from curbs, a harsher breakaway at the grip limit, and some shops won't mount extreme stretch. Bulge (wide tire on a narrow rim): sloppy steering response and the sidewall rolls under in hard cornering. Square (tire width matched to rim): the best handling and the safest — this is what we recommend for anyone who drives hard.
Staggered setups
Wider wheels and tires in the rear (common on RWD cars like BMW, Mustang, 370Z): keep the front-to-rear overall diameter within 1% of each other or you'll confuse traction control and ABS. And never stagger an AWD car beyond what the manufacturer allows — center differentials are expensive.