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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 1 + 1 ⁄ 4" (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 ...
One standard option for the Brompton folding bicycle is to use a 3-speed hub gear (roughly a 30% difference between gear ratios) in combination with a 2-speed derailleur gear (roughly a 15% difference) to give 6 distinct gear ratios; this is an example of half-step gearing. Some Brompton suppliers offer a 2-speed chainring 'Mountain Drive' as ...
The fitness and cadence of the rider, bicycle tire pressure and sizes, gear ratios, slope of the terrain affect the overall speed of the rider. A person pedalling with 100 W power can achieve 5.5 m/s on a roadster, 7.5 m/s on a racing bicycle, 10 m/s with a faired HPV and 14 m/s with an ultimate HPV.
Crawl ratio is a term used in the automotive world to describe the highest gear ratio that a vehicle is capable of. Note that gear ratio, also known as speed ratio, of a gear train is defined as the ratio of the angular velocity of the input gear to the angular velocity of the output gear, and thus a higher gear ratio implies a larger speed reduction, i.e. the input speed is reduced more at ...
The rotational speed of the wheels for that given forward speed is simple to calculate, being the tire circumference multiplied by the RPM. [a] As the tire RPM at maximum speed is not the same as the engine RPM at that power, a transmission is used with a gear ratio to convert one to the other. [b]
Prior to 1964, tires were all made to a 90% aspect ratio. Tire size was specified as the tire width in inches and the diameter in inches – for example, 6.50-15. [24] From 1965 to the early 1970s, tires were made to an 80% aspect ratio. Tire size was again specified by width in inches and diameter in inches.
In cycling, cadence is a measure of rotational speed of the crank, expressed in units of revolutions per minute (r/min or rpm). In other words, it is the pedalling rate at which a cyclist is turning the pedals. Cadence is directly proportional to wheel speed, but is a distinct measurement and changes
Racing bicycles have a relatively narrow gear range and typically vary from medium to very high ratios, distributed across 18, 20, 27, or 30 gears. The more closely spaced gear ratios allow racers to choose a gear that will enable them to ride at their optimum pedaling cadence for maximum efficiency.