245/50R20 vs 255/55R20
255/55R20 is outside the ±3% rule as a replacement for 245/50R20: the diameter differs by +4.71%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 255/55R20 on a car calibrated for 245/50R20, 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 245/50R20
- 245/50R20 vs 245/45R20-3.25%
- 245/50R20 vs 255/45R20-2.06%
- 245/50R20 vs 255/50R20+1.33%
- 245/50R20 vs 275/40R20-3.32%
- 245/50R20 vs 265/50R20+2.66%
- 245/50R20 vs 275/45R20+0.33%
- 245/50R20 vs 235/55R20+1.79%
- 245/50R20 vs 245/55R19-0.12%
- 245/50R20 vs 265/45R20-0.86%
- 245/50R20 vs 265/50R19-0.72%
- 245/50R20 vs 315/35R20-3.25%
- 245/50R20 vs 275/50R20+3.98%
Questions
Can I replace 245/50R20 with 255/55R20?
255/55R20 is outside the ±3% rule as a replacement for 245/50R20: the diameter differs by +4.71%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 245/50R20 and 255/55R20?
255/55R20 is 1.40" taller and 10 mm wider; the sidewall is +0.70". At an indicated 60 mph you'd actually be doing 62.8 mph.
Will 255/55R20 fit on 245/50R20 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.