ElpiAuto235/75R17 vs 305/70R17
305/70R17 is 2.93″ (75 mm) taller than 235/75R17, a 9.5% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
The section widths are very different — these are not a like-for-like swap. Confirm wheel width and arch clearance separately.
| Measurement | 235/75R17 | 305/70R17 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 30.88″ | 33.81″ | +2.93″ | +9.5% |
| Section width | 9.25″ | 12.01″ | +2.76″ | +29.8% |
| Sidewall height | 6.94″ | 8.41″ | +1.47″ | +21.1% |
| Circumference | 97.01″ | 106.22″ | +9.21″ | +9.5% |
| Revs per mile | 653.2 | 596.5 | −56.7 | −8.7% |
| Revs per km | 405.9 | 370.6 | −35.2 | −8.7% |
Speedometer: with 235/75R17 as the original, 305/70R17 makes an indicated 60 mph really about 65.7 mph, and the axle sits ~1.47″ 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.