equivalent to doubling the size of the drive wheel; that is, it is like a directly driven bicycle with a 52-inch wheel. That gear is said to be "52 gear inches." A bicycle with a 26-inch wheel, a 48-tooth chainring, and a cassette with gears ranging from 11 to 34 teeth has a lowest gear of 26 × 48 / 34 = 37 gear inches and a highest gear of 26 × 48 / 11 = 113 gear inches. For bicycles with 700c wheels, some cyclists quote gear inches based on a nominal wheel diameter of 27 inches, corresponding to the old British tire size of 27 x 1¼" (ETRTO 630). Strictly speaking, the rolling diameter of a 700c wheel may be significantly higher or lower than 27", depending on the tire size, e.g. nearly 27.5" for a 700x38 tire, or just over 26" for a 700x20 tire. This can be the source of some confusion when comparing gears unless it is clear whether gear inches have been calculated using the actual wheel size or a conventionalised 27". One way to estimate wheel diameter is to add twice the nominal tyre cross-section to the rim diameter. For example, consider a 700c × 23 mm tire, which has a nominal cross-section of 23 mm. 700c wheels have a rim diameter of 622 mm. Hence the wheel diameter is (2 × 23 mm) + 622 mm = 668 mm which is equal to 26.3 inches (rounded to 1 decimal place). 26 inch mountain bicycle wheels have a rim diameter of 559 mm. This ignores factors that contribute to the actual rolling radius of the tyre and rim together: the vertical deflection of the tire above the contact patch and the difference between the manufacturer's stated size and the actual tire radius when mounted and inflated. Gear inches, along with cadence, can be converted to speed as follows: Relationship to metres of development An equivalent system customarily used by continental European cyclists is metres of development, which measures the distance travelled with each turn of the crank. That is, metres of development is calculated as (normally rounded to one decimal place): Thus gear inches and development differ by a factor of π times imperial-to-metric conversion. To convert from gear inches to metres of development, multiply by 0.08 (more precisely: 0.0254π). Regulations Up until 2023, the UCI limited junior riders to 7.93 metres of