ElpiAuto35X12.50R18 vs 37X12.50R18
37X12.50R18 is 2.00″ (51 mm) taller than 35X12.50R18, a 5.7% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
| Measurement | 35X12.50R18 | 37X12.50R18 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 35.00″ | 37.00″ | +2.00″ | +5.7% |
| Section width | 12.50″ | 12.50″ | — | |
| Sidewall height | 8.50″ | 9.50″ | +1.00″ | +11.8% |
| Circumference | 109.96″ | 116.24″ | +6.28″ | +5.7% |
| Revs per mile | 576.2 | 545.1 | −31.1 | −5.4% |
| Revs per km | 358.1 | 338.7 | −19.4 | −5.4% |
Speedometer: with 35X12.50R18 as the original, 37X12.50R18 makes an indicated 60 mph really about 63.4 mph, and the axle sits ~1.00″ higher.
Reading this comparison
The overall diameter is what matters here: 37X12.50R18 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.