275/45R18 vs 245/55R18
245/55R18 is outside the ±3% rule as a replacement for 275/45R18: the diameter differs by +3.12%, 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 275/45R18, the speedometer reads 58.2 mph when you're really doing 60, and the odometer under-counts by 3.1%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.9 mph |
| 45 mph | 46.4 mph |
| 60 mph | 61.9 mph |
| 70 mph | 72.2 mph |
| 80 mph | 82.5 mph |
Other sizes close to 275/45R18
- 275/45R18 vs 235/60R18+4.90%
- 275/45R18 vs 245/45R18-3.83%
- 275/45R18 vs 235/50R18-1.77%
- 275/45R18 vs 235/55R18+1.56%
- 275/45R18 vs 245/45R19-0.23%
- 275/45R18 vs 225/60R18+3.19%
- 275/45R18 vs 225/50R18-3.19%
- 275/45R18 vs 225/60R17-0.41%
- 275/45R18 vs 225/55R180.00%
- 275/45R18 vs 255/55R18+4.68%
- 275/45R18 vs 275/40R19-0.30%
- 275/45R18 vs 215/65R17+0.94%
Questions
Can I replace 275/45R18 with 245/55R18?
245/55R18 is outside the ±3% rule as a replacement for 275/45R18: the diameter differs by +3.12%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 275/45R18 and 245/55R18?
245/55R18 is 0.87" taller and 30 mm narrower; the sidewall is +0.43". At an indicated 60 mph you'd actually be doing 61.9 mph.
Will 245/55R18 fit on 275/45R18 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.