235/65R18 vs 255/65R17
255/65R17 is a safe swap for 235/65R18 by the usual ±3% rule: the diameter differs by +0.08%.
Speedometer and odometer
With 255/65R17 on a car calibrated for 235/65R18, the speedometer reads 60.0 mph when you're really doing 60, and the odometer under-counts by 0.1%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.0 mph |
| 45 mph | 45.0 mph |
| 60 mph | 60.0 mph |
| 70 mph | 70.1 mph |
| 80 mph | 80.1 mph |
Other sizes close to 235/65R18
- 235/65R18 vs 235/60R18-3.08%
- 235/65R18 vs 265/60R18+1.64%
- 235/65R18 vs 225/60R18-4.65%
- 235/65R18 vs 245/60R18-1.51%
- 235/65R18 vs 255/55R18-3.28%
- 235/65R18 vs 255/65R18+3.41%
- 235/65R18 vs 255/55R19+0.05%
- 235/65R18 vs 255/60R18+0.07%
- 235/65R18 vs 245/55R18-4.72%
- 235/65R18 vs 285/60R18+4.79%
- 235/65R18 vs 235/70R17-0.25%
- 235/65R18 vs 275/60R18+3.21%
Questions
Can I replace 235/65R18 with 255/65R17?
255/65R17 is a safe swap for 235/65R18 by the usual ±3% rule: the diameter differs by +0.08%.
What's the difference between 235/65R18 and 255/65R17?
255/65R17 is 0.02" taller and 20 mm wider; the sidewall is +0.51". At an indicated 60 mph you'd actually be doing 60.0 mph.
Will 255/65R17 fit on 235/65R18 wheels?
No — 235/65R18 needs a 18" wheel and 255/65R17 a 17" wheel. This is a plus/minus-size swap that changes wheels too.