ElpiAuto275/55R20 vs 285/50R20
285/50R20 is 0.69″ (17 mm) shorter than 275/55R20, a 2.2% 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 | 275/55R20 | 285/50R20 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 31.91″ | 31.22″ | −0.69″ | −2.2% |
| Section width | 10.83″ | 11.22″ | +0.39″ | +3.6% |
| Sidewall height | 5.95″ | 5.61″ | −0.34″ | −5.8% |
| Circumference | 100.25″ | 98.08″ | −2.16″ | −2.2% |
| Revs per mile | 632.0 | 646.0 | +13.9 | +2.2% |
| Revs per km | 392.7 | 401.4 | +8.7 | +2.2% |
Speedometer: with 275/55R20 as the original, 285/50R20 makes an indicated 60 mph really about 58.7 mph, and the axle sits ~0.34″ lower.
Reading this comparison
The overall diameter is what matters here: 275/55R20 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.