245/45R18 vs 215/55R18
215/55R18 is a safe swap for 245/45R18 by the usual ±3% rule: the diameter differs by +2.36%.
Speedometer and odometer
With 215/55R18 on a car calibrated for 245/45R18, the speedometer reads 58.6 mph when you're really doing 60, and the odometer under-counts by 2.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.7 mph |
| 45 mph | 46.1 mph |
| 60 mph | 61.4 mph |
| 70 mph | 71.7 mph |
| 80 mph | 81.9 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 215/55R18?
215/55R18 is a safe swap for 245/45R18 by the usual ±3% rule: the diameter differs by +2.36%.
What's the difference between 245/45R18 and 215/55R18?
215/55R18 is 0.63" taller and 30 mm narrower; the sidewall is +0.31". At an indicated 60 mph you'd actually be doing 61.4 mph.
Will 215/55R18 fit on 245/45R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 215 mm tire and the fender clearance.