285/35R18 vs 255/45R18
255/45R18 is outside the ±3% rule as a replacement for 285/35R18: the diameter differs by +4.57%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 255/45R18 on a car calibrated for 285/35R18, the speedometer reads 57.4 mph when you're really doing 60, and the odometer under-counts by 4.6%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.4 mph |
| 45 mph | 47.1 mph |
| 60 mph | 62.7 mph |
| 70 mph | 73.2 mph |
| 80 mph | 83.7 mph |
Other sizes close to 285/35R18
- 285/35R18 vs 225/45R18+0.46%
- 285/35R18 vs 245/40R18-0.53%
- 285/35R18 vs 225/40R18-2.97%
- 285/35R18 vs 225/50R17+0.02%
- 285/35R18 vs 245/45R18+3.20%
- 285/35R18 vs 235/45R18+1.83%
- 285/35R18 vs 235/40R18-1.75%
- 285/35R18 vs 225/50R18+3.88%
- 285/35R18 vs 245/45R17-0.67%
- 285/35R18 vs 255/35R19+0.67%
- 285/35R18 vs 255/35R18-3.20%
- 285/35R18 vs 255/40R18+0.69%
Questions
Can I replace 285/35R18 with 255/45R18?
255/45R18 is outside the ±3% rule as a replacement for 285/35R18: the diameter differs by +4.57%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 285/35R18 and 255/45R18?
255/45R18 is 1.18" taller and 30 mm narrower; the sidewall is +0.59". At an indicated 60 mph you'd actually be doing 62.7 mph.
Will 255/45R18 fit on 285/35R18 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.