ElpiAuto245/75R17 vs 315/70R17
315/70R17 is 2.89″ (74 mm) taller than 245/75R17, a 9.2% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
The section widths are very different — these are not a like-for-like swap. Confirm wheel width and arch clearance separately.
| Measurement | 245/75R17 | 315/70R17 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 31.47″ | 34.36″ | +2.89″ | +9.2% |
| Section width | 9.65″ | 12.40″ | +2.76″ | +28.6% |
| Sidewall height | 7.23″ | 8.68″ | +1.45″ | +20.0% |
| Circumference | 98.86″ | 107.95″ | +9.09″ | +9.2% |
| Revs per mile | 640.9 | 586.9 | −54.0 | −8.4% |
| Revs per km | 398.2 | 364.7 | −33.5 | −8.4% |
Speedometer: with 245/75R17 as the original, 315/70R17 makes an indicated 60 mph really about 65.5 mph, and the axle sits ~1.45″ higher.
Reading this comparison
The overall diameter is what matters here: 315/70R17 is the taller tire. It sets ride height, gearing and how far the tire travels per revolution — which is what the speedometer and odometer count. Width and sidewall change fit and feel (a wider tire needs a wider wheel and more clearance; a shorter sidewall sharpens steering) but not the gearing.
Figures are geometric estimates from the size codes; real moulded tires vary by brand by 1–3%. Confirm load rating, wheel width and physical clearance on your vehicle before fitting. To compare any other two sizes, use the tire size comparison tool; to decode one size and see what else fits its wheel, the tire size calculator.