ElpiAuto235/55R17 vs 245/45R17
245/45R17 is 1.50″ (38 mm) shorter than 235/55R17, a 5.5% difference in overall diameter — outside the ±3% band, so expect the speedometer to drift and check for rubbing before fitting.
| Measurement | 235/55R17 | 245/45R17 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 27.18″ | 25.68″ | −1.50″ | −5.5% |
| Section width | 9.25″ | 9.65″ | +0.39″ | +4.3% |
| Sidewall height | 5.09″ | 4.34″ | −0.75″ | −14.7% |
| Circumference | 85.38″ | 80.68″ | −4.70″ | −5.5% |
| Revs per mile | 742.1 | 785.3 | +43.2 | +5.8% |
| Revs per km | 461.1 | 488.0 | +26.9 | +5.8% |
Speedometer: with 235/55R17 as the original, 245/45R17 makes an indicated 60 mph really about 56.7 mph, and the axle sits ~0.75″ lower.
Reading this comparison
The overall diameter is what matters here: 235/55R17 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.