215/45R18 vs 265/40R18
265/40R18 is a safe swap for 215/45R18 by the usual ±3% rule: the diameter differs by +2.84%.
Speedometer and odometer
With 265/40R18 on a car calibrated for 215/45R18, the speedometer reads 58.3 mph when you're really doing 60, and the odometer under-counts by 2.8%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.9 mph |
| 45 mph | 46.3 mph |
| 60 mph | 61.7 mph |
| 70 mph | 72.0 mph |
| 80 mph | 82.3 mph |
Other sizes close to 215/45R18
- 215/45R18 vs 245/40R18+0.38%
- 215/45R18 vs 225/45R18+1.38%
- 215/45R18 vs 225/40R18-2.07%
- 215/45R18 vs 225/50R17+0.94%
- 215/45R18 vs 245/45R18+4.15%
- 215/45R18 vs 235/45R18+2.77%
- 215/45R18 vs 235/40R18-0.85%
- 215/45R18 vs 225/50R18+4.84%
- 215/45R18 vs 215/50R17-0.60%
- 215/45R18 vs 245/45R17+0.25%
- 215/45R18 vs 255/35R18-2.31%
- 215/45R18 vs 255/40R18+1.61%
Questions
Can I replace 215/45R18 with 265/40R18?
265/40R18 is a safe swap for 215/45R18 by the usual ±3% rule: the diameter differs by +2.84%.
What's the difference between 215/45R18 and 265/40R18?
265/40R18 is 0.73" taller and 50 mm wider; the sidewall is +0.36". At an indicated 60 mph you'd actually be doing 61.7 mph.
Will 265/40R18 fit on 215/45R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 265 mm tire and the fender clearance.