ElpiAuto275/70R18 vs 33X12.50R18
33X12.50R18 is 0.16″ (4 mm) shorter than 275/70R18, a 0.5% difference in overall diameter — comfortably inside the ±3% band most fitment guides use, so it swaps straight across for gearing and the speedometer.
| Measurement | 275/70R18 | 33X12.50R18 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 33.16″ | 33.00″ | −0.16″ | −0.5% |
| Section width | 10.83″ | 12.50″ | +1.67″ | +15.5% |
| Sidewall height | 7.58″ | 7.50″ | −0.08″ | −1.0% |
| Circumference | 104.17″ | 103.67″ | −0.49″ | −0.5% |
| Revs per mile | 608.3 | 611.2 | +2.9 | +0.5% |
| Revs per km | 378.0 | 379.8 | +1.8 | +0.5% |
Speedometer: with 275/70R18 as the original, 33X12.50R18 makes an indicated 60 mph really about 59.7 mph, and the axle sits ~0.08″ lower.
Reading this comparison
The overall diameter is what matters here: 275/70R18 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.