245/40R17 vs 255/40R17
255/40R17 is a safe swap for 245/40R17 by the usual ±3% rule: the diameter differs by +1.27%.
Speedometer and odometer
With 255/40R17 on a car calibrated for 245/40R17, 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 | 81.0 mph |
Other sizes close to 245/40R17
- 245/40R17 vs 225/45R17+1.04%
- 245/40R17 vs 225/50R17+4.62%
- 245/40R17 vs 205/55R16+0.65%
- 245/40R17 vs 215/45R17-0.40%
- 245/40R17 vs 205/50R17+1.43%
- 245/40R17 vs 215/50R17+3.03%
- 245/40R17 vs 235/45R17+2.47%
- 245/40R17 vs 245/45R17+3.90%
- 245/40R17 vs 205/45R17-1.83%
- 245/40R17 vs 245/35R18+0.14%
- 245/40R17 vs 225/50R16+0.57%
- 245/40R17 vs 205/55R17+4.70%
Questions
Can I replace 245/40R17 with 255/40R17?
255/40R17 is a safe swap for 245/40R17 by the usual ±3% rule: the diameter differs by +1.27%.
What's the difference between 245/40R17 and 255/40R17?
255/40R17 is 0.31" taller and 10 mm wider; the sidewall is +0.16". At an indicated 60 mph you'd actually be doing 60.8 mph.
Will 255/40R17 fit on 245/40R17 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.