ElpiAuto235/45R17 vs 245/45R17
245/45R17 is 0.35″ (9 mm) taller than 235/45R17, a 1.4% difference in overall diameter — comfortably inside the ±3% band most fitment guides use, so it swaps straight across for gearing and the speedometer.
| Measurement | 235/45R17 | 245/45R17 | Difference | % |
|---|---|---|---|---|
| Overall diameter | 25.33″ | 25.68″ | +0.35″ | +1.4% |
| Section width | 9.25″ | 9.65″ | +0.39″ | +4.3% |
| Sidewall height | 4.16″ | 4.34″ | +0.18″ | +4.3% |
| Circumference | 79.57″ | 80.68″ | +1.11″ | +1.4% |
| Revs per mile | 796.3 | 785.3 | −11.0 | −1.4% |
| Revs per km | 494.8 | 488.0 | −6.8 | −1.4% |
Speedometer: with 235/45R17 as the original, 245/45R17 makes an indicated 60 mph really about 60.8 mph, and the axle sits ~0.18″ higher.
Reading this comparison
The overall diameter is what matters here: 245/45R17 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.