275/45R19 tyre size
A 275/45R19 tyre is 275 mm (10.8") wide with a sidewall height of 45 % of the width, i.e. 123.8 mm (4.9"), on a 19" (483 mm) rim. Overall diameter is 730.1 mm (28.7"), so the closest inch-style size is 28.7×10.8R19. Static circumference is 2294 mm; the ETRTO rolling circumference is 2227 mm, giving 449 revolutions per km (723 per mile).
Dimensions and rolling diameter
| Section width | 275 mm | 10.83″ |
| Sidewall height | 123.8 mm | 4.87″ |
| Rim diameter | 482.6 mm | 19″ |
| Overall diameter (static, unloaded) | 730.1 mm | 28.74″ |
| Static radius | 365.0 mm | 14.37″ |
| Static circumference (π × D) | 2,294 mm | 90.3″ |
| Rolling circumference (ETRTO 3.05 × D) | 2,227 mm | 87.7″ |
| Effective rolling radius | 354.4 mm | 13.95″ |
| Revs per km (rolling / static) | 449 / 436 | |
| Inch equivalent | 28.7×10.8R19 | |
| Approved rim widths (approx.) | 8.5″–10″ (measuring rim 9″) | |
A 275/45R19 tyre is 275 mm (10.8") wide with a sidewall height of 45 % of the width, i.e. 123.8 mm (4.9"), on a 19" (483 mm) rim. Overall diameter is 730.1 mm (28.7"), so the closest inch-style size is 28.7×10.8R19. Static circumference is 2294 mm; the ETRTO rolling circumference is 2227 mm, giving 449 revolutions per km (723 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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