ElpiAuto285/55R20 vs 315/60R20
315/60R20 is 2.54″ (64 mm) taller than 285/55R20, a 7.9% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
| Measurement | 285/55R20 | 315/60R20 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 32.34″ | 34.88″ | +2.54″ | +7.9% |
| Section width | 11.22″ | 12.40″ | +1.18″ | +10.5% |
| Sidewall height | 6.17″ | 7.44″ | +1.27″ | +20.6% |
| Circumference | 101.61″ | 109.58″ | +7.98″ | +7.9% |
| Revs per mile | 623.6 | 578.2 | −45.4 | −7.3% |
| Revs per km | 387.5 | 359.3 | −28.2 | −7.3% |
Speedometer: with 285/55R20 as the original, 315/60R20 makes an indicated 60 mph really about 64.7 mph, and the axle sits ~1.27″ higher.
Reading this comparison
The overall diameter is what matters here: 315/60R20 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.