ElpiAuto285/50R20 vs 285/55R20
285/55R20 is 1.12″ (29 mm) taller than 285/50R20, a 3.6% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
| Measurement | 285/50R20 | 285/55R20 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 31.22″ | 32.34″ | +1.12″ | +3.6% |
| Section width | 11.22″ | 11.22″ | — | |
| Sidewall height | 5.61″ | 6.17″ | +0.56″ | +10.0% |
| Circumference | 98.08″ | 101.61″ | +3.53″ | +3.6% |
| Revs per mile | 646.0 | 623.6 | −22.4 | −3.5% |
| Revs per km | 401.4 | 387.5 | −13.9 | −3.5% |
Speedometer: with 285/50R20 as the original, 285/55R20 makes an indicated 60 mph really about 62.2 mph, and the axle sits ~0.56″ higher.
Reading this comparison
The overall diameter is what matters here: 285/55R20 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.