ElpiAuto275/70R18 vs 375/70R18
375/70R18 is 5.51″ (140 mm) taller than 275/70R18, a 16.6% 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 | 275/70R18 | 375/70R18 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 33.16″ | 38.67″ | +5.51″ | +16.6% |
| Section width | 10.83″ | 14.76″ | +3.94″ | +36.4% |
| Sidewall height | 7.58″ | 10.33″ | +2.76″ | +36.4% |
| Circumference | 104.17″ | 121.48″ | +17.32″ | +16.6% |
| Revs per mile | 608.3 | 521.6 | −86.7 | −14.3% |
| Revs per km | 378.0 | 324.1 | −53.9 | −14.3% |
Speedometer: with 275/70R18 as the original, 375/70R18 makes an indicated 60 mph really about 70.0 mph, and the axle sits ~2.76″ higher.
Reading this comparison
The overall diameter is what matters here: 375/70R18 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.