How the speed switch works on a bicycle


The switch looks and works mysteriously, especially for a novice cyclist. But first, let’s look at what parts the switch is made of and where it came from. By the way, the current version of the rear derailleur is quite old. It was invented by the Italian Tullio Campagnolo back in 1950.

For a long time remaining an attribute of expensive sports and road models, it was only in the 80s that this switch began to appear on city bicycles, and in the mid-1990s it became the de facto standard for most designs.


The rollers in the gear selector are different, and when repairing or cleaning, it is very important not to confuse them, since the life of the chain depends on this, and the switch itself.

The guide roller, aka G-pulley, or guid pulley, is upper. performs several tasks at once:

  • Directs the chain to the stars.
  • Compensates for backlash due to small horizontal displacements.
  • Increases feed smoothness and reduces noise due to small grooves on the teeth.

T-pulley, also known as tension pulley, is a tension pulley that prevents the chain from sagging.

Spring direction

The standard operating procedure for a spring is when the chain is thrown onto the larger stars by force from the shifter, and to the smaller ones by the spring. This principle is universal, and so far, the reverse device, when smaller stars correspond to a lower number on the derailleur, remains an experiment of Shimano, losing to the classics in resistance to dirt and damage.


Several things are configured in these devices:

speed, switch, works, bicycle
  • The tension of the cable and its movement. with the help of shifters and a special tightening screw.
  • The extreme positions of the frame with the designations High and Low. to limit movement.
  • Stroke and proportionality of the shift with the adjusting screw.

There are certain rules for measuring and positioning the frame, chain and stars, but it is better to read more about them in our material on setting up bicycle derailleurs.

Bicycle rear derailleur

Many bicycle lovers, while riding, gradually master the tuning and minor repairs of their bikes: here. tighten the brakes, there. change the saddle. But when it comes to the rear derailleur, a lot of people fail. Such a complex and not completely clear design raises more questions than answers, and portends difficulties not even in setting up, but in installing and removing.

Principles of operation and maintenance

In the end. a little about the switch operation procedure.

Main elements

What is the rear derailleur design? Before examining how this device works, consider the design:

  • The frame is the most noticeable part, which, by its displacement, throws the chain between the stars of the cassette. The frame is made of durable materials and closes on both sides with different rollers.
  • The guide roller is the small roller that the chain hits first. He guides the chain between the cassette stars in the frame;
  • Tensioner roller. usually small, but different from the guide roller, which is responsible for tensioning the chain that it receives from the frame. Located at the very bottom of the switch.
  • Parallelogram mechanism. the main part, which is the articulation of several frames, pulled up by a spring.
  • The spring is usually the most important and expensive part of the switch, along with the frame and rollers, since it is responsible for returning (or pressing) the frame to one side, in fact, for the mobility of the entire structure.

In addition, the speed selector in almost all models contains elements for configuring the device:

How To Change Gear On Your Bike | Road Bike Shifting Made Easy

  • tensioner (cable) adjustment;
  • upper gear limiter. aka H, ​​High. is responsible for the extreme position of the frame with the chain;
  • lower gear limiter. L, Low. similar, but on the other side;
  • the mounting bolt is a special attachment point, usually on the cock. In other cases, the mount goes beyond the additional frame on the guides.
READ  How much to swing the wheels on a bicycle 29

About mountain biking. How to adjust the rear derailleur

Every cycling enthusiast should know how to properly adjust the rear derailleur. If the mechanism fails, its normal operation will come to naught. The operation of the rear derailleur seems to many cyclists difficult and incomprehensible, hidden from prying eyes. The mechanism can easily and unpretentiously perform its functions, but one day it will fail. If you have no experience in fixing this problem, take your bike to a workshop, where a qualified technician will fix the problem within a few minutes.

You can understand the principles of the rear derailleur. By adhering to our recommendations, you will say goodbye to the difficulties in the further maintenance of the bike on your own.

Although the gear shifters are simple at first glance, their optimal setting can seem like a rather daunting task. Gear shifting is a sequence of actions that loosen and tighten the cable. The cable without which the rear derailleur will not work. Tuning an old and worn out movement or a cheap model made of low quality metal is a big challenge. After just a couple of years of operation, backlash may form in the switch connections.

How does the rear derailleur work? For the efficiency of tuning, it is advisable to study the device of the component of interest to us. The key principle of operation is based on gear shifting when transferring the chain from one drive sprocket to another, of a different diameter. Let’s start by comparing the front and rear derailleurs. Structurally, the front derailleur is a regular steel frame that moves in different directions. During movement, this chain shifts to the side, from one sprocket to the next.

The rear derailleur has a more complex mechanism. It has a special spring-loaded foot with small rollers. By dropping the chain onto smaller sprockets, the cyclist uses a shifter to loosen the cable, thereby shifting the chain to the desired sprockets. For chain transfer to a larger sprocket, the shift process is slightly different. In this case, the cable is pulled, after which the foot brings the chain to the star of a larger diameter, friction occurs until it is picked up by the tooth, which will send it to a new gear.

Reasons for the malfunction of the rear derailleur 1) Mechanical failure. The gear shifter most often breaks down due to mechanical damage, for example, when a cyclist falls on the track. The first step is to make sure it isn’t bent. Ideally, the foot should be parallel to the cassette stars. If there is even a slight bias, you can judge the deformation of the cock (rear derailleur bracket), and not the derailleur itself. Often, after impact, the switch is bent inward, closer to the spokes. Sometimes it hits the knitting needles. It is bad if the frame is not equipped with a removable bracket. then the spokes break, the derailleur and the dropout. all this leads to a breakdown of the frame. The bracket is attached to the frame with a bolt and the rear derailleur is attached to the second bracket. Straightens in a simple way. just pull the switch. But this only works with a slight deviation. Otherwise, you just have to replace the rooster; 2) Poor cable lubrication and contamination; 3) Incorrectly adjusted rear derailleur; 4) Deterioration of related parts. Worn out sprockets and flails, rollers in poor condition also lead to breakage. By themselves, poor quality rear derailleur models often break down. A lot of problems can be caused when shifting gears and a malfunction of the shifter.

How Do Bike Gears Work? | Bicycle Gears Explained

If you experience difficulty in shifting gears and the bike is unruly on the move, take a close look at the bike. When adjusting, do not pull on the rear derailleur foot only, as this may lead to deformation.

READ  How to adjust hydraulic disc brakes on a bicycle

The necessary tools are required for you: hex keys or a set of them (a 3- and 5-mm key is required), a Phillips screwdriver. Before starting debugging, it is important to make sure that the switch is still functional.

speed, switch, works, bicycle

Preparatory phase The gear selector is a delicate mechanism in a hard-to-reach place. Therefore, before starting direct adjustment, it is necessary to eliminate key obstacles to the quality of the procedure.

Pay attention to the cleanliness of the bike, its individual mechanisms associated with the operation of the switch. Take care of your bike chain lubrication. Next, the bicycle chain is moved to such a position that it becomes on the small stars in front and behind at the same time. To do this, find on the switch the adjusting screws with the inscriptions H and L. It is necessary to unscrew the screw under the letter L as much as possible.

Then unscrew the cable tensioner clockwise as far as it will go. A similar one is located on the shifter. The procedure should be repeated with it. Remember that the rear derailleurs of different models have five key parts: 1) Bolt and nut for securing the cable; 2) Screw with hollowness and cable tension adjustment; 3) Screw for limiting the stroke, is transferred to the largest sprocket (L); 4) Limiting screw for small sprocket (H); 5) Tensioning screw for the chain.

Some cheap models do not have cable and chain tensioners. The final preparatory operation is to unscrew the screw that secures the cable directly to the switch. If rust forms, it must be replaced. Slight wear of the part indicates further operation with a prerequisite for cleaning and lubrication. Place the chain on the smallest chainring at the front and the largest chainring at the back, then pedal backwards. Then the upper roller of the rear derailleur, turning the tension screw, bring it as close to the star as possible, but so that it does not touch it. Such actions will help to achieve smooth gear shifting. At the end of the preparation, check that the cable slides easily through the shirt on the bike frame. Sometimes it needs to be rinsed.

Basic setup Begin adjusting by checking the position of the top roller. it should be on the same vertical cutter line or slightly to the left of the smallest cassette star above it, or slightly offset to the left when viewed from the rear. You can correct the position using the adjusting screw marked H. To move the roller to the left, turn the screw clockwise, to move it to the right. vice versa. Set up the high gear limiter as follows: 1) put the largest sprocket in the front and the smallest in the back; 2) loosen the shifting cable by unscrewing the switch holding bolt. You can screw in the cable tension adjustments on the switch and on the shifter to the maximum; 3) make sure that both rollers are in the same plane with the smallest sprocket; 4) at the end of the adjustment, it is necessary to pull the cable and clamp it on the switch.

After installing the cable, you need to go to the setting of small gears. Place the chain on the rear sprocket with the largest diameter. Next, check the position of the rollers under the large sprocket. The bolt responsible for the position of the rollers is located under the letter L. Adjust the chain if the speed switch has the ability to adjust the level of its tension. Each cyclist selects the optimal settings for himself. it is advisable to remember them in order to ensure a comfortable use of the bike.

Tension Adjustment Modern models have two spring-loaded levers. The lower one raises the switch frame upward, when positioned on small stars. The upper one provides movement of the frame back to the large star. The spring tension of both levers must be balanced for correct gear shifting.

READ  How to change the cable on a stealth bike

By setting the chain to the lowest gear, when the screw is loosened, the guide roller rises, approaching the sprocket, reducing the angle of inclination of the chain. this improves the quality of shifting. The roller should not touch the sprocket and the gap should be approximately 5 mm. It is advisable to do this procedure when replacing the cassette or when changing the length of the chain.

How to Shift Correctly After setting the rear derailleur, you need to make sure that the gears are shifted correctly. Thoughtless flicking of the switch is not the best solution for checking the functionality of the switch. The key rule is that gear changes are carried out while the bike is moving. Before changing the speed, it is advisable to apply less pedal pressure. Change gears sequentially. If you want to climb a mountain on the move, change the gear to a lighter one before starting the actual climb. To descend from a hill, the same rule is relevant, but you only need to switch to a gear in which it is more difficult to pedal.

Combinations of the right sprocket for different rides Experienced cyclists select the optimal sprocket combination for a comfortable ride for their bike model. The most popular combination can be called: for city driving and asphalt roadway outside the city. a large front and between the 4th and 8th rear sprockets; for cross-country travel or for fast driving on the track. a combination of a large chainring with driven ones (3rd and 6th); when going uphill. a combination of a small leading star with driven ones (from 1st to 3rd).

Too much misalignment of the chain will shorten its life. As soon as there is a sudden extraneous sound when driving, stop immediately and check the switch for faults.

Caring for cables and shirts Sometimes it is enough to keep the shirts and cables clean and lubricate them regularly with liquid oil. It is then much easier to adjust the bike’s rear derailleur. Switches of different rulers and manufacturers serve different periods. it all depends on the price range. But even the durability of cheap switches can be extended with gentle handling and care.

A cable shirt is needed to keep out dirt. If you find a torn cable with loose threads, then hurry up to replace it with a new one. In case of corrosion of the cable and constant jamming in the jacket, it is better to treat it with graphite grease. The rear derailleur adjustment will then advance faster and the gear shifting will remain as smooth as before. Damaged shirts should be replaced.

Diagnostics of the problem with the rooster If the chain throwing by the rear derailleur fails, there is a reason to check the rooster for serviceability. The rear derailleur often suffers from damage. There is a huge load on it. Often from a strong blow to the log and the curb, the rooster bends or bursts. Therefore, make sure that the two tensioner rollers are strictly vertical to each other.

The dissonance of the geometrical parallels of the rollers means breakage. The chain, passing along the rollers, must be strictly vertical. without distortions. Do not level him in a field, forest, snowy mountains. Trying to straighten it by hand will only bend the switch frame. Experts do not recommend that you straighten a bent cock by pulling on the switch. Its frame is very fragile. First, it will bend, then the fasteners will deteriorate. this will only aggravate the situation with the repair. It is better to completely remove the cock, spread it out on a flat surface and use tools in attempts to straighten.

By following our instructions, you can independently consolidate your theoretical knowledge of a bicycle in practice. No one but you can actually make it work: only you know all its pros and cons.