Modern bicycles have the mechanisms of switching of speeds working due to jumping of the chain from one star for another. Therefore the maximum quantity of speeds depends on quantity of stars.
At modern bicycles the maximum number of speeds can reach 30. The number of speeds depends on quantity of front and back stars. The speed selector by bicycle is necessary for comfortable driving on the cross-country terrain. For example, at run on the height, it is necessary to switch speed to low gears, and it is necessary to go from the hill on the overgear. Switching speeds, when necessary, the cyclist saves the forces.
How to determine number of speeds
The nominal number of speeds is defined by options of combinations of front and back stars. For example, if at the bicycle of 10 back stars and 3 lobbies, then the nominal number of speeds is equal 30 and if behind 9 stars, then 27. However there is one nuance — the actual number of speeds which can be used, will be less. It is connected with the fact that because of the distortion and the wrong tension of the chain it isn't necessary to use all possible combinations of stars.
Optimum switching of speeds
In order to avoid the distortion and the soskakivaniye of the chain it is recommended to switch speeds as follows: • The first front star works with back stars in combinations 1-1, 1-2, 1-3 and 1-4. • The second front star works with back stars in combinations 2-4, 2-5, 2-6 and 2-7.• third front star works with back stars in combinations 3-6, 3-7, 3-8 and 3-9. As a result it turns out that the bicycle with three front and nine back stars nominally has 27 speeds (3*9=27), but actually it will use only 12 speeds. And it is enough for trips around the area with any relief. It should be notedIt should be noted that it isn't obligatory to adhere to this scheme at all, but when using optimum combinations of switching of stars the wear of the chain significantly decreases.
As it is correct to switch speeds
When driving against wind, on sand, clay, wet dirt or rise uphill, it is necessary "to dump" the front pass. Then will easier twist pedals, to maneuver and gather speed. The first front pass is optimum for rise if you don't want to use the great physical efforts. The second pass is suitable for small rises and driving on forest drags. It is recommended to switch to the third front pass (biggest star) during driving on the city. At the same time the reverse gear switches according to the scheme of switching of speeds given above.