215/40R17 vs 215/45R17
215/45R17 is outside the ±3% rule as a replacement for 215/40R17: the diameter differs by +3.56%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 215/45R17 on a car calibrated for 215/40R17, the speedometer reads 57.9 mph when you're really doing 60, and the odometer under-counts by 3.6%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.1 mph |
| 45 mph | 46.6 mph |
| 60 mph | 62.1 mph |
| 70 mph | 72.5 mph |
| 80 mph | 82.8 mph |
Other sizes close to 215/40R17
Questions
Can I replace 215/40R17 with 215/45R17?
215/45R17 is outside the ±3% rule as a replacement for 215/40R17: the diameter differs by +3.56%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 215/40R17 and 215/45R17?
215/45R17 is 0.85" taller and 0 mm wider; the sidewall is +0.42". At an indicated 60 mph you'd actually be doing 62.1 mph.
Will 215/45R17 fit on 215/40R17 wheels?
Both use a 17" rim, so the wheel diameter matches; check the wheel's width range for a 215 mm tire and the fender clearance.