ElpiAuto285/75R18 vs 325/60R18
325/60R18 is 1.48″ (37 mm) shorter than 285/75R18, a 4.2% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
| Measurement | 285/75R18 | 325/60R18 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 34.83″ | 33.35″ | −1.48″ | −4.2% |
| Section width | 11.22″ | 12.80″ | +1.57″ | +14.0% |
| Sidewall height | 8.42″ | 7.68″ | −0.74″ | −8.8% |
| Circumference | 109.42″ | 104.79″ | −4.64″ | −4.2% |
| Revs per mile | 579.0 | 604.7 | +25.6 | +4.4% |
| Revs per km | 359.8 | 375.7 | +15.9 | +4.4% |
Speedometer: with 285/75R18 as the original, 325/60R18 makes an indicated 60 mph really about 57.5 mph, and the axle sits ~0.74″ lower.
Reading this comparison
The overall diameter is what matters here: 285/75R18 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.