245/40R17 vs 245/45R17
245/45R17 is outside the ±3% rule as a replacement for 245/40R17: the diameter differs by +3.90%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 245/45R17 on a car calibrated for 245/40R17, the speedometer reads 57.7 mph when you're really doing 60, and the odometer under-counts by 3.9%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.2 mph |
| 45 mph | 46.8 mph |
| 60 mph | 62.3 mph |
| 70 mph | 72.7 mph |
| 80 mph | 83.1 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 205/45R17-1.83%
- 245/40R17 vs 255/40R17+1.27%
- 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 245/45R17?
245/45R17 is outside the ±3% rule as a replacement for 245/40R17: the diameter differs by +3.90%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 245/40R17 and 245/45R17?
245/45R17 is 0.96" taller and 0 mm wider; the sidewall is +0.48". At an indicated 60 mph you'd actually be doing 62.3 mph.
Will 245/45R17 fit on 245/40R17 wheels?
Both use a 17" rim, so the wheel diameter matches; check the wheel's width range for a 245 mm tire and the fender clearance.