255/60R17 vs 235/60R18
235/60R18 is a safe swap for 255/60R17 by the usual ±3% rule: the diameter differs by +0.19%.
Speedometer and odometer
With 235/60R18 on a car calibrated for 255/60R17, the speedometer reads 59.9 mph when you're really doing 60, and the odometer under-counts by 0.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.1 mph |
| 60 mph | 60.1 mph |
| 70 mph | 70.1 mph |
| 80 mph | 80.2 mph |
Other sizes close to 255/60R17
- 255/60R17 vs 225/65R17-1.83%
- 255/60R17 vs 235/65R17-0.07%
- 255/60R17 vs 225/60R17-4.88%
- 255/60R17 vs 245/65R17+1.69%
- 255/60R17 vs 255/55R18-0.01%
- 255/60R17 vs 225/75R16+0.83%
- 255/60R17 vs 235/70R16-0.33%
- 255/60R17 vs 235/60R17-3.25%
- 255/60R17 vs 215/65R17-3.59%
- 255/60R17 vs 255/65R17+3.46%
- 255/60R17 vs 235/70R17+3.12%
- 255/60R17 vs 255/65R16+0.01%
Questions
Can I replace 255/60R17 with 235/60R18?
235/60R18 is a safe swap for 255/60R17 by the usual ±3% rule: the diameter differs by +0.19%.
What's the difference between 255/60R17 and 235/60R18?
235/60R18 is 0.06" taller and 20 mm narrower; the sidewall is -0.47". At an indicated 60 mph you'd actually be doing 60.1 mph.
Will 235/60R18 fit on 255/60R17 wheels?
No — 255/60R17 needs a 17" wheel and 235/60R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.