ElpiAuto30X9.50R15 vs 33X12.50R15
33X12.50R15 is 3.00″ (76 mm) taller than 30X9.50R15, a 10.0% 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 | 30X9.50R15 | 33X12.50R15 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 30.00″ | 33.00″ | +3.00″ | +10.0% |
| Section width | 9.50″ | 12.50″ | +3.00″ | +31.6% |
| Sidewall height | 7.50″ | 9.00″ | +1.50″ | +20.0% |
| Circumference | 94.25″ | 103.67″ | +9.42″ | +10.0% |
| Revs per mile | 672.3 | 611.2 | −61.1 | −9.1% |
| Revs per km | 417.7 | 379.8 | −38.0 | −9.1% |
Speedometer: with 30X9.50R15 as the original, 33X12.50R15 makes an indicated 60 mph really about 66.0 mph, and the axle sits ~1.50″ higher.
Reading this comparison
The overall diameter is what matters here: 33X12.50R15 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.