235/75R17 vs 255/65R18
255/65R18 is a safe swap for 235/75R17 by the usual ±3% rule: the diameter differs by +0.56%.
Speedometer and odometer
With 255/65R18 on a car calibrated for 235/75R17, the speedometer reads 59.7 mph when you're really doing 60, and the odometer under-counts by 0.6%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.2 mph |
| 45 mph | 45.3 mph |
| 60 mph | 60.3 mph |
| 70 mph | 70.4 mph |
| 80 mph | 80.4 mph |
Other sizes close to 235/75R17
- 235/75R17 vs 265/70R17+2.36%
- 235/75R17 vs 245/70R17-1.21%
- 235/75R17 vs 245/65R17-4.34%
- 235/75R17 vs 245/75R17+1.91%
- 235/75R17 vs 265/65R17-1.02%
- 235/75R17 vs 265/70R16-0.88%
- 235/75R17 vs 235/80R17+3.00%
- 235/75R17 vs 255/65R17-2.68%
- 235/75R17 vs 255/70R17+0.57%
- 235/75R17 vs 255/75R17+3.83%
- 235/75R17 vs 275/70R17+4.14%
- 235/75R17 vs 235/70R17-3.00%
Questions
Can I replace 235/75R17 with 255/65R18?
255/65R18 is a safe swap for 235/75R17 by the usual ±3% rule: the diameter differs by +0.56%.
What's the difference between 235/75R17 and 255/65R18?
255/65R18 is 0.17" taller and 20 mm wider; the sidewall is -0.41". At an indicated 60 mph you'd actually be doing 60.3 mph.
Will 255/65R18 fit on 235/75R17 wheels?
No — 235/75R17 needs a 17" wheel and 255/65R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.