255/60R18 vs 285/60R18
285/60R18 is outside the ±3% rule as a replacement for 255/60R18: the diameter differs by +4.72%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 285/60R18 on a car calibrated for 255/60R18, the speedometer reads 57.3 mph when you're really doing 60, and the odometer under-counts by 4.7%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.4 mph |
| 45 mph | 47.1 mph |
| 60 mph | 62.8 mph |
| 70 mph | 73.3 mph |
| 80 mph | 83.8 mph |
Other sizes close to 255/60R18
- 255/60R18 vs 235/60R18-3.14%
- 255/60R18 vs 265/60R18+1.57%
- 255/60R18 vs 225/60R18-4.72%
- 255/60R18 vs 245/60R18-1.57%
- 255/60R18 vs 255/55R18-3.34%
- 255/60R18 vs 235/65R18-0.07%
- 255/60R18 vs 255/65R18+3.34%
- 255/60R18 vs 255/55R19-0.01%
- 255/60R18 vs 255/65R17+0.01%
- 255/60R18 vs 245/55R18-4.78%
- 255/60R18 vs 235/70R17-0.31%
- 255/60R18 vs 275/60R18+3.14%
Questions
Can I replace 255/60R18 with 285/60R18?
285/60R18 is outside the ±3% rule as a replacement for 255/60R18: the diameter differs by +4.72%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 255/60R18 and 285/60R18?
285/60R18 is 1.42" taller and 30 mm wider; the sidewall is +0.71". At an indicated 60 mph you'd actually be doing 62.8 mph.
Will 285/60R18 fit on 255/60R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 285 mm tire and the fender clearance.