245/50R18 vs 255/55R18
255/55R18 is outside the ±3% rule as a replacement for 245/50R18: the diameter differs by +5.06%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 255/55R18 on a car calibrated for 245/50R18, the speedometer reads 57.1 mph when you're really doing 60, and the odometer under-counts by 5.1%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.5 mph |
| 45 mph | 47.3 mph |
| 60 mph | 63.0 mph |
| 70 mph | 73.5 mph |
| 80 mph | 84.0 mph |
Other sizes close to 245/50R18
- 245/50R18 vs 245/45R18-3.49%
- 245/50R18 vs 235/50R18-1.42%
- 245/50R18 vs 235/55R18+1.92%
- 245/50R18 vs 235/45R18-4.77%
- 245/50R18 vs 245/45R19+0.13%
- 245/50R18 vs 225/60R18+3.56%
- 245/50R18 vs 225/50R18-2.85%
- 245/50R18 vs 225/60R17-0.06%
- 245/50R18 vs 225/55R18+0.36%
- 245/50R18 vs 275/40R19+0.06%
- 245/50R18 vs 255/45R18-2.21%
- 245/50R18 vs 215/55R18-1.21%
Questions
Can I replace 245/50R18 with 255/55R18?
255/55R18 is outside the ±3% rule as a replacement for 245/50R18: the diameter differs by +5.06%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 245/50R18 and 255/55R18?
255/55R18 is 1.40" taller and 10 mm wider; the sidewall is +0.70". At an indicated 60 mph you'd actually be doing 63.0 mph.
Will 255/55R18 fit on 245/50R18 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.