225/45R15 vs 175/65R15
175/65R15 is outside the ±3% rule as a replacement for 225/45R15: the diameter differs by +4.28%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 175/65R15 on a car calibrated for 225/45R15, the speedometer reads 57.5 mph when you're really doing 60, and the odometer under-counts by 4.3%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.3 mph |
| 45 mph | 46.9 mph |
| 60 mph | 62.6 mph |
| 70 mph | 73.0 mph |
| 80 mph | 83.4 mph |
Other sizes close to 225/45R15
Questions
Can I replace 225/45R15 with 175/65R15?
175/65R15 is outside the ±3% rule as a replacement for 225/45R15: the diameter differs by +4.28%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 225/45R15 and 175/65R15?
175/65R15 is 0.98" taller and 50 mm narrower; the sidewall is +0.49". At an indicated 60 mph you'd actually be doing 62.6 mph.
Will 175/65R15 fit on 225/45R15 wheels?
Both use a 15" rim, so the wheel diameter matches; check the wheel's width range for a 175 mm tire and the fender clearance.