285/75R17 vs 315/70R17
315/70R17 is a safe swap for 285/75R17 by the usual ±3% rule: the diameter differs by +1.57%.
Speedometer and odometer
With 315/70R17 on a car calibrated for 285/75R17, the speedometer reads 59.1 mph when you're really doing 60, and the odometer under-counts by 1.6%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.5 mph |
| 45 mph | 45.7 mph |
| 60 mph | 60.9 mph |
| 70 mph | 71.1 mph |
| 80 mph | 81.3 mph |
Other sizes close to 285/75R17
Questions
Can I replace 285/75R17 with 315/70R17?
315/70R17 is a safe swap for 285/75R17 by the usual ±3% rule: the diameter differs by +1.57%.
What's the difference between 285/75R17 and 315/70R17?
315/70R17 is 0.53" taller and 30 mm wider; the sidewall is +0.27". At an indicated 60 mph you'd actually be doing 60.9 mph.
Will 315/70R17 fit on 285/75R17 wheels?
Both use a 17" rim, so the wheel diameter matches; check the wheel's width range for a 315 mm tire and the fender clearance.