305/65R17 vs 255/80R17
255/80R17 is a safe swap for 305/65R17 by the usual ±3% rule: the diameter differs by +1.39%.
Speedometer and odometer
With 255/80R17 on a car calibrated for 305/65R17, the speedometer reads 59.2 mph when you're really doing 60, and the odometer under-counts by 1.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.4 mph |
| 45 mph | 45.6 mph |
| 60 mph | 60.8 mph |
| 70 mph | 71.0 mph |
| 80 mph | 81.1 mph |
Other sizes close to 305/65R17
- 305/65R17 vs 265/70R17-3.08%
- 305/65R17 vs 285/70R17+0.30%
- 305/65R17 vs 245/75R17-3.50%
- 305/65R17 vs 265/70R18-0.01%
- 305/65R17 vs 235/80R17-2.47%
- 305/65R17 vs 285/75R16+0.68%
- 305/65R17 vs 285/65R18-0.07%
- 305/65R17 vs 255/70R17-4.77%
- 305/65R17 vs 255/75R17-1.69%
- 305/65R17 vs 295/70R17+1.99%
- 305/65R17 vs 305/70R16+0.62%
- 305/65R17 vs 285/75R17+3.74%
Questions
Can I replace 305/65R17 with 255/80R17?
255/80R17 is a safe swap for 305/65R17 by the usual ±3% rule: the diameter differs by +1.39%.
What's the difference between 305/65R17 and 255/80R17?
255/80R17 is 0.45" taller and 50 mm narrower; the sidewall is +0.23". At an indicated 60 mph you'd actually be doing 60.8 mph.
Will 255/80R17 fit on 305/65R17 wheels?
Both use a 17" rim, so the wheel diameter matches; check the wheel's width range for a 255 mm tire and the fender clearance.