ElpiAuto285/50R20 vs 35X12.50R20
35X12.50R20 is 3.78″ (96 mm) taller than 285/50R20, a 12.1% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
The sidewall heights are very different — ride and steering feel will change noticeably even though the diameter is close.
| Measurement | 285/50R20 | 35X12.50R20 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 31.22″ | 35.00″ | +3.78″ | +12.1% |
| Section width | 11.22″ | 12.50″ | +1.28″ | +11.4% |
| Sidewall height | 5.61″ | 7.50″ | +1.89″ | +33.7% |
| Circumference | 98.08″ | 109.96″ | +11.87″ | +12.1% |
| Revs per mile | 646.0 | 576.2 | −69.8 | −10.8% |
| Revs per km | 401.4 | 358.1 | −43.3 | −10.8% |
Speedometer: with 285/50R20 as the original, 35X12.50R20 makes an indicated 60 mph really about 67.3 mph, and the axle sits ~1.89″ higher.
Reading this comparison
The overall diameter is what matters here: 35X12.50R20 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.