235/50R18 vs 245/55R18
245/55R18 is outside the ±3% rule as a replacement for 235/50R18: the diameter differs by +4.98%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 245/55R18 on a car calibrated for 235/50R18, the speedometer reads 57.2 mph when you're really doing 60, and the odometer under-counts by 5.0%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.5 mph |
| 45 mph | 47.2 mph |
| 60 mph | 63.0 mph |
| 70 mph | 73.5 mph |
| 80 mph | 84.0 mph |
Other sizes close to 235/50R18
- 235/50R18 vs 225/45R18-4.70%
- 235/50R18 vs 245/45R18-2.09%
- 235/50R18 vs 235/45R18-3.39%
- 235/50R18 vs 235/55R18+3.39%
- 235/50R18 vs 235/55R17-0.27%
- 235/50R18 vs 225/50R18-1.44%
- 235/50R18 vs 255/40R19-0.81%
- 235/50R18 vs 225/55R18+1.81%
- 235/50R18 vs 255/40R18-4.48%
- 235/50R18 vs 215/60R17-0.35%
- 235/50R18 vs 245/50R18+1.44%
- 235/50R18 vs 255/45R18-0.79%
Questions
Can I replace 235/50R18 with 245/55R18?
245/55R18 is outside the ±3% rule as a replacement for 235/50R18: the diameter differs by +4.98%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 235/50R18 and 245/55R18?
245/55R18 is 1.36" taller and 10 mm wider; the sidewall is +0.68". At an indicated 60 mph you'd actually be doing 63.0 mph.
Will 245/55R18 fit on 235/50R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 245 mm tire and the fender clearance.