ElpiAuto305/70R17 vs 37X12.50R17
37X12.50R17 is 3.19″ (81 mm) taller than 305/70R17, a 9.4% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
| Measurement | 305/70R17 | 37X12.50R17 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 33.81″ | 37.00″ | +3.19″ | +9.4% |
| Section width | 12.01″ | 12.50″ | +0.49″ | +4.1% |
| Sidewall height | 8.41″ | 10.00″ | +1.59″ | +19.0% |
| Circumference | 106.22″ | 116.24″ | +10.02″ | +9.4% |
| Revs per mile | 596.5 | 545.1 | −51.4 | −8.6% |
| Revs per km | 370.6 | 338.7 | −31.9 | −8.6% |
Speedometer: with 305/70R17 as the original, 37X12.50R17 makes an indicated 60 mph really about 65.7 mph, and the axle sits ~1.59″ higher.
Reading this comparison
The overall diameter is what matters here: 37X12.50R17 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.