245/45R18 vs 255/45R18
255/45R18 is a safe swap for 245/45R18 by the usual ±3% rule: the diameter differs by +1.33%.
Speedometer and odometer
With 255/45R18 on a car calibrated for 245/45R18, the speedometer reads 59.2 mph when you're really doing 60, and the odometer under-counts by 1.3%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.4 mph |
| 45 mph | 45.6 mph |
| 60 mph | 60.8 mph |
| 70 mph | 70.9 mph |
| 80 mph | 81.1 mph |
Other sizes close to 245/45R18
- 245/45R18 vs 225/45R18-2.66%
- 245/45R18 vs 245/40R18-3.62%
- 245/45R18 vs 225/55R17+0.24%
- 245/45R18 vs 235/50R18+2.14%
- 245/45R18 vs 235/45R18-1.33%
- 245/45R18 vs 245/40R19+0.13%
- 245/45R18 vs 235/40R18-4.80%
- 245/45R18 vs 225/50R18+0.66%
- 245/45R18 vs 225/55R18+3.98%
- 245/45R18 vs 255/40R18-2.43%
- 245/45R18 vs 275/35R19-0.38%
- 245/45R18 vs 245/50R18+3.62%
Questions
Can I replace 245/45R18 with 255/45R18?
255/45R18 is a safe swap for 245/45R18 by the usual ±3% rule: the diameter differs by +1.33%.
What's the difference between 245/45R18 and 255/45R18?
255/45R18 is 0.35" taller and 10 mm wider; the sidewall is +0.18". At an indicated 60 mph you'd actually be doing 60.8 mph.
Will 255/45R18 fit on 245/45R18 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.