ElpiAuto285/60R20 vs 315/60R20
315/60R20 is 1.42″ (36 mm) taller than 285/60R20, a 4.2% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
| Measurement | 285/60R20 | 315/60R20 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 33.46″ | 34.88″ | +1.42″ | +4.2% |
| Section width | 11.22″ | 12.40″ | +1.18″ | +10.5% |
| Sidewall height | 6.73″ | 7.44″ | +0.71″ | +10.5% |
| Circumference | 105.13″ | 109.58″ | +4.45″ | +4.2% |
| Revs per mile | 602.7 | 578.2 | −24.5 | −4.1% |
| Revs per km | 374.5 | 359.3 | −15.2 | −4.1% |
Speedometer: with 285/60R20 as the original, 315/60R20 makes an indicated 60 mph really about 62.5 mph, and the axle sits ~0.71″ 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.