ElpiAuto285/70R17 vs 305/70R17
305/70R17 is 1.10″ (28 mm) taller than 285/70R17, a 3.4% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
| Measurement | 285/70R17 | 305/70R17 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 32.71″ | 33.81″ | +1.10″ | +3.4% |
| Section width | 11.22″ | 12.01″ | +0.79″ | +7.0% |
| Sidewall height | 7.85″ | 8.41″ | +0.55″ | +7.0% |
| Circumference | 102.76″ | 106.22″ | +3.46″ | +3.4% |
| Revs per mile | 616.6 | 596.5 | −20.1 | −3.3% |
| Revs per km | 383.1 | 370.6 | −12.5 | −3.3% |
Speedometer: with 285/70R17 as the original, 305/70R17 makes an indicated 60 mph really about 62.0 mph, and the axle sits ~0.55″ higher.
Reading this comparison
The overall diameter is what matters here: 305/70R17 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.