255/65R18 vs 255/70R18
255/70R18 is outside the ±3% rule as a replacement for 255/65R18: the diameter differs by +3.23%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 255/70R18 on a car calibrated for 255/65R18, the speedometer reads 58.1 mph when you're really doing 60, and the odometer under-counts by 3.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.0 mph |
| 45 mph | 46.5 mph |
| 60 mph | 61.9 mph |
| 70 mph | 72.3 mph |
| 80 mph | 82.6 mph |
Other sizes close to 255/65R18
- 255/65R18 vs 275/65R18+3.30%
- 255/65R18 vs 265/60R18-1.71%
- 255/65R18 vs 245/60R18-4.75%
- 255/65R18 vs 265/65R18+1.65%
- 255/65R18 vs 235/65R18-3.30%
- 255/65R18 vs 255/60R19-0.01%
- 255/65R18 vs 285/65R18+4.94%
- 255/65R18 vs 255/70R17+0.01%
- 255/65R18 vs 255/60R18-3.23%
- 255/65R18 vs 235/75R17-0.56%
- 255/65R18 vs 285/60R18+1.33%
- 255/65R18 vs 275/55R19-0.46%
Questions
Can I replace 255/65R18 with 255/70R18?
255/70R18 is outside the ±3% rule as a replacement for 255/65R18: the diameter differs by +3.23%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 255/65R18 and 255/70R18?
255/70R18 is 1.00" taller and 0 mm wider; the sidewall is +0.50". At an indicated 60 mph you'd actually be doing 61.9 mph.
Will 255/70R18 fit on 255/65R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 255 mm tire and the fender clearance.