255/80R17 vs 305/70R17
305/70R17 is a safe swap for 255/80R17 by the usual ±3% rule: the diameter differs by +2.26%.
Speedometer and odometer
With 305/70R17 on a car calibrated for 255/80R17, the speedometer reads 58.7 mph when you're really doing 60, and the odometer under-counts by 2.3%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.7 mph |
| 45 mph | 46.0 mph |
| 60 mph | 61.4 mph |
| 70 mph | 71.6 mph |
| 80 mph | 81.8 mph |
Other sizes close to 255/80R17
- 255/80R17 vs 265/70R17-4.41%
- 255/80R17 vs 275/70R18+0.29%
- 255/80R17 vs 285/70R17-1.07%
- 255/80R17 vs 245/75R17-4.82%
- 255/80R17 vs 235/80R17-3.81%
- 255/80R17 vs 285/75R16-0.70%
- 255/80R17 vs 315/70R17+3.93%
- 255/80R17 vs 255/75R17-3.04%
- 255/80R17 vs 295/70R17+0.60%
- 255/80R17 vs 33x12.50R18-0.19%
- 255/80R17 vs 305/70R16-0.76%
- 255/80R17 vs 285/75R17+2.32%
Questions
Can I replace 255/80R17 with 305/70R17?
305/70R17 is a safe swap for 255/80R17 by the usual ±3% rule: the diameter differs by +2.26%.
What's the difference between 255/80R17 and 305/70R17?
305/70R17 is 0.75" taller and 50 mm wider; the sidewall is +0.37". At an indicated 60 mph you'd actually be doing 61.4 mph.
Will 305/70R17 fit on 255/80R17 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.