285/70R17 vs 305/70R17
305/70R17 is outside the ±3% rule as a replacement for 285/70R17: the diameter differs by +3.37%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 305/70R17 on a car calibrated for 285/70R17, the speedometer reads 58.0 mph when you're really doing 60, and the odometer under-counts by 3.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.0 mph |
| 45 mph | 46.5 mph |
| 60 mph | 62.0 mph |
| 70 mph | 72.4 mph |
| 80 mph | 82.7 mph |
Other sizes close to 285/70R17
- 285/70R17 vs 265/70R17-3.37%
- 285/70R17 vs 245/75R17-3.79%
- 285/70R17 vs 265/70R18-0.31%
- 285/70R17 vs 235/80R17-2.77%
- 285/70R17 vs 285/75R16+0.37%
- 285/70R17 vs 285/65R18-0.37%
- 285/70R17 vs 255/75R17-1.99%
- 285/70R17 vs 295/70R17+1.69%
- 285/70R17 vs 305/70R16+0.31%
- 285/70R17 vs 33x12.50R18+0.89%
- 285/70R17 vs 285/75R17+3.43%
- 285/70R17 vs 33x12.50R17+0.89%
Questions
Can I replace 285/70R17 with 305/70R17?
305/70R17 is outside the ±3% rule as a replacement for 285/70R17: the diameter differs by +3.37%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 285/70R17 and 305/70R17?
305/70R17 is 1.10" taller and 20 mm wider; the sidewall is +0.55". At an indicated 60 mph you'd actually be doing 62.0 mph.
Will 305/70R17 fit on 285/70R17 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.