255/50R20 vs 285/50R20
285/50R20 is outside the ±3% rule as a replacement for 255/50R20: the diameter differs by +3.93%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 285/50R20 on a car calibrated for 255/50R20, the speedometer reads 57.7 mph when you're really doing 60, and the odometer under-counts by 3.9%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.2 mph |
| 45 mph | 46.8 mph |
| 60 mph | 62.4 mph |
| 70 mph | 72.8 mph |
| 80 mph | 83.1 mph |
Other sizes close to 255/50R20
- 255/50R20 vs 245/45R20-4.52%
- 255/50R20 vs 255/45R20-3.34%
- 255/50R20 vs 275/40R20-4.59%
- 255/50R20 vs 265/50R20+1.31%
- 255/50R20 vs 245/50R20-1.31%
- 255/50R20 vs 275/45R20-0.98%
- 255/50R20 vs 255/55R20+3.34%
- 255/50R20 vs 235/55R20+0.46%
- 255/50R20 vs 265/45R20-2.16%
- 255/50R20 vs 255/55R19+0.01%
- 255/50R20 vs 315/35R20-4.52%
- 255/50R20 vs 275/50R20+2.62%
Questions
Can I replace 255/50R20 with 285/50R20?
285/50R20 is outside the ±3% rule as a replacement for 255/50R20: the diameter differs by +3.93%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 255/50R20 and 285/50R20?
285/50R20 is 1.18" taller and 30 mm wider; the sidewall is +0.59". At an indicated 60 mph you'd actually be doing 62.4 mph.
Will 285/50R20 fit on 255/50R20 wheels?
Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 285 mm tire and the fender clearance.