275/55R19 tyre size
A 275/55R19 tyre is 275 mm (10.8") wide with a sidewall height of 55 % of the width, i.e. 151.3 mm (6.0"), on a 19" (483 mm) rim. Overall diameter is 785.1 mm (30.9"), so the closest inch-style size is 30.9×10.8R19. Static circumference is 2466 mm; the ETRTO rolling circumference is 2395 mm, giving 418 revolutions per km (672 per mile).
Dimensions and rolling diameter
| Section width | 275 mm | 10.83″ |
| Sidewall height | 151.3 mm | 5.95″ |
| Rim diameter | 482.6 mm | 19″ |
| Overall diameter (static, unloaded) | 785.1 mm | 30.91″ |
| Static radius | 392.5 mm | 15.45″ |
| Static circumference (π × D) | 2,466 mm | 97.1″ |
| Rolling circumference (ETRTO 3.05 × D) | 2,395 mm | 94.3″ |
| Effective rolling radius | 381.1 mm | 15.00″ |
| Revs per km (rolling / static) | 418 / 405 | |
| Inch equivalent | 30.9×10.8R19 | |
| Approved rim widths (approx.) | 7.5″–9.5″ (measuring rim 8.5″) | |
A 275/55R19 tyre is 275 mm (10.8") wide with a sidewall height of 55 % of the width, i.e. 151.3 mm (6.0"), on a 19" (483 mm) rim. Overall diameter is 785.1 mm (30.9"), so the closest inch-style size is 30.9×10.8R19. Static circumference is 2466 mm; the ETRTO rolling circumference is 2395 mm, giving 418 revolutions per km (672 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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