235/60R18 vs 255/60R18
255/60R18 is outside the ±3% rule as a replacement for 235/60R18: the diameter differs by +3.25%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 255/60R18 on a car calibrated for 235/60R18, 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 235/60R18
- 235/60R18 vs 235/55R19+0.26%
- 235/60R18 vs 235/55R18-3.18%
- 235/60R18 vs 235/65R17-0.26%
- 235/60R18 vs 265/60R18+4.87%
- 235/60R18 vs 225/60R18-1.62%
- 235/60R18 vs 255/50R19-0.22%
- 235/60R18 vs 245/60R18+1.62%
- 235/60R18 vs 225/55R18-4.67%
- 235/60R18 vs 255/55R18-0.20%
- 235/60R18 vs 235/65R18+3.18%
- 235/60R18 vs 245/55R18-1.69%
- 235/60R18 vs 255/60R17-0.19%
Questions
Can I replace 235/60R18 with 255/60R18?
255/60R18 is outside the ±3% rule as a replacement for 235/60R18: the diameter differs by +3.25%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 235/60R18 and 255/60R18?
255/60R18 is 0.94" taller and 20 mm wider; the sidewall is +0.47". At an indicated 60 mph you'd actually be doing 61.9 mph.
Will 255/60R18 fit on 235/60R18 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.