ElpiAuto245/75R17 vs 305/70R17
305/70R17 is 2.34″ (60 mm) taller than 245/75R17, a 7.4% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
| Measurement | 245/75R17 | 305/70R17 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 31.47″ | 33.81″ | +2.34″ | +7.4% |
| Section width | 9.65″ | 12.01″ | +2.36″ | +24.5% |
| Sidewall height | 7.23″ | 8.41″ | +1.17″ | +16.2% |
| Circumference | 98.86″ | 106.22″ | +7.36″ | +7.4% |
| Revs per mile | 640.9 | 596.5 | −44.4 | −6.9% |
| Revs per km | 398.2 | 370.6 | −27.6 | −6.9% |
Speedometer: with 245/75R17 as the original, 305/70R17 makes an indicated 60 mph really about 64.5 mph, and the axle sits ~1.17″ 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.