ElpiAuto275/65R20 vs 285/55R20
285/55R20 is 1.73″ (44 mm) shorter than 275/65R20, a 5.1% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
| Measurement | 275/65R20 | 285/55R20 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 34.07″ | 32.34″ | −1.73″ | −5.1% |
| Section width | 10.83″ | 11.22″ | +0.39″ | +3.6% |
| Sidewall height | 7.04″ | 6.17″ | −0.87″ | −12.3% |
| Circumference | 107.05″ | 101.61″ | −5.44″ | −5.1% |
| Revs per mile | 591.9 | 623.6 | +31.7 | +5.4% |
| Revs per km | 367.8 | 387.5 | +19.7 | +5.4% |
Speedometer: with 275/65R20 as the original, 285/55R20 makes an indicated 60 mph really about 56.9 mph, and the axle sits ~0.87″ lower.
Reading this comparison
The overall diameter is what matters here: 275/65R20 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.