ElpiAuto305/70R17 vs 315/70R17
315/70R17 is 0.55″ (14 mm) taller than 305/70R17, a 1.6% difference in overall diameter — right at the edge of the ±3% band — fine on most cars, but check clearance at full lock and full suspension compression.
| Measurement | 305/70R17 | 315/70R17 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 33.81″ | 34.36″ | +0.55″ | +1.6% |
| Section width | 12.01″ | 12.40″ | +0.39″ | +3.3% |
| Sidewall height | 8.41″ | 8.68″ | +0.28″ | +3.3% |
| Circumference | 106.22″ | 107.95″ | +1.73″ | +1.6% |
| Revs per mile | 596.5 | 586.9 | −9.6 | −1.6% |
| Revs per km | 370.6 | 364.7 | −5.9 | −1.6% |
Speedometer: with 305/70R17 as the original, 315/70R17 makes an indicated 60 mph really about 61.0 mph, and the axle sits ~0.28″ 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.