245/45R17 tyre size
A 245/45R17 tyre is 245 mm (9.6") wide with a sidewall height of 45 % of the width, i.e. 110.3 mm (4.3"), on a 17" (432 mm) rim. Overall diameter is 652.3 mm (25.7"), so the closest inch-style size is 25.7×9.6R17. Static circumference is 2049 mm; the ETRTO rolling circumference is 1990 mm, giving 503 revolutions per km (809 per mile).
Dimensions and rolling diameter
| Section width | 245 mm | 9.65″ |
| Sidewall height | 110.3 mm | 4.34″ |
| Rim diameter | 431.8 mm | 17″ |
| Overall diameter (static, unloaded) | 652.3 mm | 25.68″ |
| Static radius | 326.2 mm | 12.84″ |
| Static circumference (π × D) | 2,049 mm | 80.7″ |
| Rolling circumference (ETRTO 3.05 × D) | 1,990 mm | 78.3″ |
| Effective rolling radius | 316.6 mm | 12.47″ |
| Revs per km (rolling / static) | 503 / 488 | |
| Inch equivalent | 25.7×9.6R17 | |
| Approved rim widths (approx.) | 7.5″–9″ (measuring rim 8″) | |
A 245/45R17 tyre is 245 mm (9.6") wide with a sidewall height of 45 % of the width, i.e. 110.3 mm (4.3"), on a 17" (432 mm) rim. Overall diameter is 652.3 mm (25.7"), so the closest inch-style size is 25.7×9.6R17. Static circumference is 2049 mm; the ETRTO rolling circumference is 1990 mm, giving 503 revolutions per km (809 per mile).
Why two circumferences? The static figure is simple geometry (π × diameter). Under load a radial tyre flattens and rolls about 3 % less per revolution; ETRTO defines the rolling circumference as 3.05 × the nominal diameter, which is what manufacturers quote and what speedo and gearing calculations should use.
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