255/70R17 vs 305/65R17
305/65R17 is outside the ±3% rule as a replacement for 255/70R17: the diameter differs by +5.01%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 305/65R17 on a car calibrated for 255/70R17, the speedometer reads 57.1 mph when you're really doing 60, and the odometer under-counts by 5.0%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.5 mph |
| 45 mph | 47.3 mph |
| 60 mph | 63.0 mph |
| 70 mph | 73.5 mph |
| 80 mph | 84.0 mph |
Other sizes close to 255/70R17
- 255/70R17 vs 265/70R17+1.77%
- 255/70R17 vs 245/70R17-1.77%
- 255/70R17 vs 245/65R17-4.88%
- 255/70R17 vs 245/75R17+1.33%
- 255/70R17 vs 265/65R17-1.58%
- 255/70R17 vs 235/80R17+2.41%
- 255/70R17 vs 255/65R18-0.01%
- 255/70R17 vs 255/65R17-3.23%
- 255/70R17 vs 255/75R17+3.23%
- 255/70R17 vs 235/75R17-0.57%
- 255/70R17 vs 275/70R17+3.55%
- 255/70R17 vs 235/70R17-3.55%
Questions
Can I replace 255/70R17 with 305/65R17?
305/65R17 is outside the ±3% rule as a replacement for 255/70R17: the diameter differs by +5.01%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 255/70R17 and 305/65R17?
305/65R17 is 1.56" taller and 50 mm wider; the sidewall is +0.78". At an indicated 60 mph you'd actually be doing 63.0 mph.
Will 305/65R17 fit on 255/70R17 wheels?
Both use a 17" rim, so the wheel diameter matches; check the wheel's width range for a 305 mm tire and the fender clearance.