285/35R20 vs 255/45R20
255/45R20 is outside the ±3% rule as a replacement for 285/35R20: the diameter differs by +4.24%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 255/45R20 on a car calibrated for 285/35R20, the speedometer reads 57.6 mph when you're really doing 60, and the odometer under-counts by 4.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.3 mph |
| 45 mph | 46.9 mph |
| 60 mph | 62.5 mph |
| 70 mph | 73.0 mph |
| 80 mph | 83.4 mph |
Other sizes close to 285/35R20
- 285/35R20 vs 245/45R19-0.62%
- 285/35R20 vs 245/45R20+2.97%
- 285/35R20 vs 275/40R20+2.90%
- 285/35R20 vs 245/40R20-0.49%
- 285/35R20 vs 255/45R19+0.65%
- 285/35R20 vs 275/40R19-0.69%
- 285/35R20 vs 245/35R20-3.96%
- 285/35R20 vs 255/35R20-2.97%
- 285/35R20 vs 255/40R20+0.64%
- 285/35R20 vs 275/35R20-0.99%
- 285/35R20 vs 315/35R20+2.97%
- 285/35R20 vs 285/30R20-4.03%
Questions
Can I replace 285/35R20 with 255/45R20?
255/45R20 is outside the ±3% rule as a replacement for 285/35R20: the diameter differs by +4.24%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 285/35R20 and 255/45R20?
255/45R20 is 1.18" taller and 30 mm narrower; the sidewall is +0.59". At an indicated 60 mph you'd actually be doing 62.5 mph.
Will 255/45R20 fit on 285/35R20 wheels?
Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 255 mm tire and the fender clearance.