215/45R17 vs 255/40R17
255/40R17 is a safe swap for 215/45R17 by the usual ±3% rule: the diameter differs by +1.68%.
Speedometer and odometer
With 255/40R17 on a car calibrated for 215/45R17, the speedometer reads 59.0 mph when you're really doing 60, and the odometer under-counts by 1.7%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.5 mph |
| 45 mph | 45.8 mph |
| 60 mph | 61.0 mph |
| 70 mph | 71.2 mph |
| 80 mph | 81.3 mph |
Other sizes close to 215/45R17
- 215/45R17 vs 225/45R17+1.44%
- 215/45R17 vs 205/50R17+1.84%
- 215/45R17 vs 215/50R17+3.44%
- 215/45R17 vs 235/45R17+2.88%
- 215/45R17 vs 245/45R17+4.32%
- 215/45R17 vs 245/40R17+0.40%
- 215/45R17 vs 205/45R17-1.44%
- 215/45R17 vs 195/55R16-0.70%
- 215/45R17 vs 245/35R18+0.54%
- 215/45R17 vs 225/50R16+0.98%
- 215/45R17 vs 275/40R17+4.24%
- 215/45R17 vs 215/40R18+0.62%
Questions
Can I replace 215/45R17 with 255/40R17?
255/40R17 is a safe swap for 215/45R17 by the usual ±3% rule: the diameter differs by +1.68%.
What's the difference between 215/45R17 and 255/40R17?
255/40R17 is 0.41" taller and 40 mm wider; the sidewall is +0.21". At an indicated 60 mph you'd actually be doing 61.0 mph.
Will 255/40R17 fit on 215/45R17 wheels?
Both use a 17" rim, so the wheel diameter matches; check the wheel's width range for a 255 mm tire and the fender clearance.