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For the wide-ratio transmission, the first gear ratio is 4:1 or 4, and in second gear it is 2:1 or 2, so the progression is equal to 4 / 2 = 2 (or 200%). For the close-ratio transmission, first gear has a 4:1 ratio or 4, and second gear has a ratio of 3:1 or 3, so the progression between gears is 4 / 3 , or 133%.
Typical gear ratios on bicycles range from very low or light gearing around 20 gear inches (1.6 metres per revolution), via medium gearing around 70 gear inches (5.6 m), to very high or heavy gearing around 125 gear inches (10 m). As in a car, low gearing is for going up hills and high gearing is for going fast.
The gearbox was designed so that, for efficiency, the fastest ratio would be a "direct-drive" or "straight-through" 1:1 ratio, avoiding frictional losses in the gears. Achieving an overdriven ratio for cruising thus required a gearbox ratio even higher than this, i.e. the gearbox output shaft rotating faster than the engine.
The steering ratio is the ratio of the number of degrees of turn of the steering wheel to the number of degrees the wheel(s) turn as a result. In motorcycles, delta tricycles and bicycles, the steering ratio is always 1:1, because the steering wheel is fixed to the front wheel. A steering ratio of x:y means that a turn of the steering wheel x ...
The rear brake of an upright bicycle can only produce about 0.25 g (≈2.5 m/s 2) deceleration at best, [87] because of the decrease in normal force at the rear wheel as described above. All such bikes with only rear braking are subject to this limitation: for example, bikes with only a coaster brake , and fixed-gear bikes with no other braking ...
The opposite effect is obtained when a large gear drives a small one. The changes are proportional to the gear ratio r, the ratio of the tooth counts: namely, T 2 / T 1 = r = N 2 / N 1 , and ω 2 / ω 1 = 1 / r = N 1 / N 2 . Depending on the geometry of the pair, the sense of rotation may also be inverted ...
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The speed ratio for a pair of meshing gears can be computed from ratio of the radii of the pitch circles and the ratio of the number of teeth on each gear, its gear ratio. Two meshing gears transmit rotational motion. The velocity v of the point of contact on the pitch circles is the same on both gears, and is given by