215/40R17 vs 245/40R17
245/40R17 is outside the ±3% rule as a replacement for 215/40R17: the diameter differs by +3.97%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 245/40R17 on a car calibrated for 215/40R17, the speedometer reads 57.7 mph when you're really doing 60, and the odometer under-counts by 4.0%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.2 mph |
| 45 mph | 46.8 mph |
| 60 mph | 62.4 mph |
| 70 mph | 72.8 mph |
| 80 mph | 83.2 mph |
Other sizes close to 215/40R17
Questions
Can I replace 215/40R17 with 245/40R17?
245/40R17 is outside the ±3% rule as a replacement for 215/40R17: the diameter differs by +3.97%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 215/40R17 and 245/40R17?
245/40R17 is 0.94" taller and 30 mm wider; the sidewall is +0.47". At an indicated 60 mph you'd actually be doing 62.4 mph.
Will 245/40R17 fit on 215/40R17 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.