ElpiAuto275/65R18 vs 285/75R18
285/75R18 is 2.76″ (70 mm) taller than 275/65R18, a 8.6% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
| Measurement | 275/65R18 | 285/75R18 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 32.07″ | 34.83″ | +2.76″ | +8.6% |
| Section width | 10.83″ | 11.22″ | +0.39″ | +3.6% |
| Sidewall height | 7.04″ | 8.42″ | +1.38″ | +19.6% |
| Circumference | 100.77″ | 109.42″ | +8.66″ | +8.6% |
| Revs per mile | 628.8 | 579.0 | −49.8 | −7.9% |
| Revs per km | 390.7 | 359.8 | −30.9 | −7.9% |
Speedometer: with 275/65R18 as the original, 285/75R18 makes an indicated 60 mph really about 65.2 mph, and the axle sits ~1.38″ higher.
Reading this comparison
The overall diameter is what matters here: 285/75R18 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.