In our country, you can meet a huge number of people who are fond of cycling. All modern bike models are already equipped with a gear shift system. Such a mechanism is simply necessary for a comfortable ride in any road conditions. Today, transmissions for bicycles come in several forms, and each is based on a specific job. To choose the most convenient option for yourself, you need to figure out what they are, how they differ and whether it is possible to independently adjust gear changes on a bicycle.
Varieties of mechanisms
Regardless of the design features, each bicycle gearshift mechanism allows the cyclist to rationally distribute his efforts on pedaling, taking into account both the force of pressing and the frequency of rotation. Thanks to this, riding on a road with obstacles becomes as easy as on smooth asphalt. All the work of the bicycle transmission is based on changing the gear ratio between the rotating wheels of the vehicle and its pedals.
This principle is common to all types of mechanisms, which can be represented as an external, internal or combined system.
The first option is found on pedal vehicles much more often than others. His work is based on the operation of two switches installed front and rear. To understand how gear shifting is done on a bicycle, you should consider each of the mechanisms separately.
Front External Flip
It is a structure with a moving frame inside, which passes the chain through itself. Thus, when shifting gears on a bicycle, along with the movement of the frame itself, the chain moves to the desired star.
The principle of operation of the mechanism is still not its only parameter when choosing, since such designs can also significantly differ from each other by such signs as:
- mounting method to the housing;
- mounting angle relative to the bike body;
- cable mounting option.
In this case, the bicycle gear shift cable can go into the switch from above, from below. It is possible to use both options. The second parameter must be selected with special attention to ensure the mechanism works as correctly as possible, and the fastening of the structure itself can be carried out with clamps or carriages. In any case, the effective operation of the mechanism is ensured only without an immediate strong load on it at the very moment of switching.
Rear gear shift mechanism
The work of this design is completely similar to the front one described above, with the only difference in a larger number of stars involved. It also has a moving frame, which simultaneously provides the necessary chain tension and does not allow it to slip in the other direction.
This bicycle gearshift mechanism also has certain parameters by which you should choose the appropriate option. You should pay attention to:
- type of attachment to the bike;
- step of a cable of switching;
- the difference in the diameter of the stars;
- type of traction.
It is interesting that the diameter of the largest star in this case will always be the same, and the choice of all the parameters listed should not be based on personal preference, but on the ideal bike model.
Pros and Cons of an External System
Among the positive aspects of this design, many distinguish simplicity, low cost, compact dimensions, and with all this a large number of gear changes. Of course, the disadvantages of external gear shifting to the bike are no less.
These include:
- high probability of breakage during a fall;
- switching only when driving;
- frequent chain wear;
- a high degree of influence of external factors on the work.
Internal switching
This mechanism is rarely found on models for mountain riding, but is often applicable to city bicycles. It is based on the work of a planetary hub, which is located at the rear and contains the entire mechanism for switching inside. Thanks to this design, only one star in front and one in the back, connected by a chain, can be seen on the outer casing of the bicycle. The number of speeds of this design is also quite large. In addition, a brake mechanism is mounted in the design.
Pros and Cons of the Internal System
In comparison with the external design, this gear shift on a bicycle can be carried out even when the pedal transport is completely stopped. Also, all working parts are located inside the sleeve, which means that they are protected from external factors, durable and reliable. The built-in brake and ease of operation should also be attributed to the advantages of the system, but there are also disadvantages. Among them, the heavy weight of the mechanism, the impossibility of self-repair on the road and the complexity of the movement during friction of nodes.
Combined system
It does not make sense to describe it in detail, since such a mechanism has collected all the shortcomings from both of the above structures. You can only meet it on city bikes, and it is a hybrid of a sleeve and a conventional external design.
The principle of the mechanism
A model of a bicycle with the ability to change speeds is most often equipped with a pair of three stars in front, called leading, and several times more stars at the back, called followers. The front stars are located so that the smallest is closest to the body of the bicycle and is considered the first. The back stars, on the contrary, are numbered from the largest, which is closest to the frame. Correct gear shifting on a bicycle should be carried out according to a certain scheme, which will not allow the chain to skew much, which leads to a quick breakdown of the entire mechanism.
So, for example, on a bicycle with three stars in front and nine in the back, switching will be as follows:
- The front large star will be involved in the chain with the rear number 7, 8 or 9, provided that you drive along a smooth track without obstacles.
- The middle chainring distributes the load along with driven stars No. 4, 5, or 6 for driving along a country road, rough roads, with wind in the face or other obstacles.
- The third leading star works in tandem with the rear stars 1, 2 or 3, creating comfortable driving conditions on an impassable road, ascent and other heavy obstacles.
Main conditions
To shift gears on a bicycle as comfortably as possible, it is not enough to take into account the degree of patency of the road. The main criterion for choosing a gear is the cadence, which ideally should be 80-110 revolutions per minute. Only at a given speed will the ride always be comfortable and not too tiring, so it is undesirable to start immediately at high speeds.
To extend the life of the transmission of your bike, you should remember that the main working star in front is the middle one, since it does not allow significant chain distortion during movement. Any chain throwing over the stars is completely controlled by the cyclist. In this case, the correct pairing algorithm described in the example above should be observed.
Speed Cycling Rules
First of all, this is an attentive handling of the whole mechanism. The chain should not be skewed during operation, and also during rotation should have a minimum rotation load. In addition, any switching should be carried out gradually. You should not "jump" immediately from first to last gear, so it is better to switch in advance before entering the mountain.
Mechanism setting
In fact, adjusting gear shifts on a bicycle is not too difficult for a cyclist and can be done independently. The need for this procedure is the presence of malfunctions during gear shifting or the inability to change gears at all. In any case, the work should begin with the setting of the rear mechanism. Let's consider everything in order.
Rear derailleur setting
Before adjusting gear changes on a bicycle, you should inspect the structure and make sure its integrity. High-quality adjustment can be made only on condition that the chain tensioner is located strictly parallel to the cassette stars.
Tuning starts with installing the chain in a place to move at the highest speed, that is, to the smallest star. After that, the adjustment takes place by tightening the screws near the chain itself. The upper one should be twisted so that its switching roller aligns with the small star, and the lower screw should align the roller with the large star. Now you need to pull the gearshift cable for the bicycle and lay it in a recess near the fixing bolt, which is then tightened. It remains only to check the quality of the work done by shifting gears and dropping speeds. If the speeds turn on poorly, then the cable tension needs to be loosened a little, but with a different adjusting mechanism on the cable mount itself. If the speed drops poorly, the cable should, on the contrary, be tightened more tightly.
After all that has been done, it remains only to ensure smooth operation of the whole structure, which is done when the chain is installed on a large star at the rear and on a small one in front. With this arrangement of the parts of the mechanism, you should tension the chain so that the upper roller is as close to the star as possible, but does not touch it. A similar work needs to be done by installing the chain in the opposite position - on a small star in the back and on the big one in front. The degree of tension is regulated by a special screw, which is located above all others.
Front derailleur setting
Before setting up gear shifting on a bicycle, you should also make sure that the whole mechanism is correctly and securely attached to the bicycle frame. After this, it is necessary to set the minimum speed and loosen the cable by adjusting the distance between the frame and the chain with the movement of the right screw. The ideal gap is a distance of one millimeter, after which the cable must be secured in a special recess near the bolt. Similar actions are carried out when setting the maximum speed, only by adjusting the left bolt. After all the manipulations, the work must be tested and, if necessary, loosen the cable tension. Such situations arise when switching poorly to small stars. Otherwise, with a bad transition to large stars, the cable will need to be pulled harder.
Based on the foregoing, it is not difficult for a beginner to independently adjust gearshifts on a bicycle, especially since every cyclist has the necessary tools for this.