ElpiAuto275/65R20 vs 315/65R20
315/65R20 is 2.05″ (52 mm) taller than 275/65R20, a 6.0% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
| Measurement | 275/65R20 | 315/65R20 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 34.07″ | 36.12″ | +2.05″ | +6.0% |
| Section width | 10.83″ | 12.40″ | +1.57″ | +14.5% |
| Sidewall height | 7.04″ | 8.06″ | +1.02″ | +14.5% |
| Circumference | 107.05″ | 113.48″ | +6.43″ | +6.0% |
| Revs per mile | 591.9 | 558.3 | −33.5 | −5.7% |
| Revs per km | 367.8 | 346.9 | −20.8 | −5.7% |
Speedometer: with 275/65R20 as the original, 315/65R20 makes an indicated 60 mph really about 63.6 mph, and the axle sits ~1.02″ higher.
Reading this comparison
The overall diameter is what matters here: 315/65R20 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.