235/70R17 vs 255/60R18
255/60R18 is a safe swap for 235/70R17 by the usual ±3% rule: the diameter differs by +0.32%.
Speedometer and odometer
With 255/60R18 on a car calibrated for 235/70R17, the speedometer reads 59.8 mph when you're really doing 60, and the odometer under-counts by 0.3%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.1 mph |
| 60 mph | 60.2 mph |
| 70 mph | 70.2 mph |
| 80 mph | 80.3 mph |
Other sizes close to 235/70R17
- 235/70R17 vs 225/65R17-4.80%
- 235/70R17 vs 235/65R17-3.09%
- 235/70R17 vs 245/65R17-1.38%
- 235/70R17 vs 245/70R17+1.84%
- 235/70R17 vs 235/65R18+0.25%
- 235/70R17 vs 265/65R17+2.04%
- 235/70R17 vs 255/65R17+0.33%
- 235/70R17 vs 255/70R16+0.34%
- 235/70R17 vs 255/70R17+3.68%
- 235/70R17 vs 235/75R17+3.09%
- 235/70R17 vs 235/75R16-0.25%
- 235/70R17 vs 255/60R17-3.02%
Questions
Can I replace 235/70R17 with 255/60R18?
255/60R18 is a safe swap for 235/70R17 by the usual ±3% rule: the diameter differs by +0.32%.
What's the difference between 235/70R17 and 255/60R18?
255/60R18 is 0.09" taller and 20 mm wider; the sidewall is -0.45". At an indicated 60 mph you'd actually be doing 60.2 mph.
Will 255/60R18 fit on 235/70R17 wheels?
No — 235/70R17 needs a 17" wheel and 255/60R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.