265/30R19 tyre size
A 265/30R19 tyre is 265 mm (10.4") wide with a sidewall height of 30 % of the width, i.e. 79.5 mm (3.1"), on a 19" (483 mm) rim. Overall diameter is 641.6 mm (25.3"), so the closest inch-style size is 25.3×10.4R19. Static circumference is 2016 mm; the ETRTO rolling circumference is 1957 mm, giving 511 revolutions per km (822 per mile).
Dimensions and rolling diameter
| Section width | 265 mm | 10.43″ |
| Sidewall height | 79.5 mm | 3.13″ |
| Rim diameter | 482.6 mm | 19″ |
| Overall diameter (static, unloaded) | 641.6 mm | 25.26″ |
| Static radius | 320.8 mm | 12.63″ |
| Static circumference (π × D) | 2,016 mm | 79.4″ |
| Rolling circumference (ETRTO 3.05 × D) | 1,957 mm | 77.0″ |
| Effective rolling radius | 311.4 mm | 12.26″ |
| Revs per km (rolling / static) | 511 / 496 | |
| Inch equivalent | 25.3×10.4R19 | |
| Approved rim widths (approx.) | 9″–10.5″ (measuring rim 9.5″) | |
A 265/30R19 tyre is 265 mm (10.4") wide with a sidewall height of 30 % of the width, i.e. 79.5 mm (3.1"), on a 19" (483 mm) rim. Overall diameter is 641.6 mm (25.3"), so the closest inch-style size is 25.3×10.4R19. Static circumference is 2016 mm; the ETRTO rolling circumference is 1957 mm, giving 511 revolutions per km (822 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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