Sizes and types
Let’s move on to the mechanics. Of course, all cyclists know in the lineup. They are brightly named and promoted, but under each sub-brand there is a number of technical characteristics, which we will now consider.
The standard spring operation is when the chain is thrown onto the larger stars by force from the lever, and to the smaller ones by the spring. This principle is universal, and so far the reverse device, when a smaller number on the derailleur corresponds to smaller stars, remains an experiment of Shimano, we are losing the classics in terms of resistance to dirt and damage.
Bicycle rear derailleur
In the process of riding, many bike lovers 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.
The de facto standard for mounting rear derailleurs is the cock. The rooster is a small bracket designed to protect the rear derailleur and reduce the force of impact to derailleurs and frame. In fact, a small fuse, because you can often hear that it is not the frame that is bent and needs to be replaced, but the bicycle cock.
Rooster frames usually have a special “eyelet”; most frames come with a ready-made rooster. In some cases, it is non-removable, i.e. It will take a fight to repair, but on most models it can be easily unmounted and replaced. Professionals recommend that you keep a close eye on the bike cock, as its deformation completely changes the mechanics of the drive system, and always for the worse, leading to wear and damage to components.
In addition to the standard, a feather mount is used. a frame element used in professional downhill bikes and various sports models to increase reliability on difficult tracks.
Several years ago, Shimano patented Shadow technology for a more compact derailleur mount, but structurally remains one of the non-standard cock mounts.
The length of the frame affects the capacity of the rear derailleur. This is the sum of the two differences. between the largest and smallest stars of the cassette and the system, i.e. The minimum required capacity for a combination of stars is calculated by the formula:
(Max1-min1) (max2. min2)
If the capacitance of the switch is less than this value, the chain will sag at certain speed combinations. If you take the switch capacity with a serious excess on the operation of the switching system This will not affect, but the risk of damage will increase, since the frame will be longer, and the switch itself is larger and heavier.
The price, of course, directly depends on the length of the frame, which, in turn, with some exceptions, correlates with the “level” of the model.
The switch looks and works mysteriously, especially for a novice cyclist. But first, let’s see what parts the switch is made of and where it came from. By the way, the current “variant” of the rear derailleur is quite old. It was invented by the Italian Tullia 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.
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, which it receives from the frame. Located at the very bottom of the switch.
- Parallelogram mechanism. the main part, representing the articulation of several frames, tightened by means of 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 setting the device:
- Tensioner (cable) adjustment
- The upper gear limiter. aka H, High. is responsible for the extreme position of the frame with the chain;
- Low gear limiter. L, Low. similar, but on the other side;
- Mounting bolt. A special attachment point, usually on the cock. In other cases, the mount goes along an additional frame on the guides.
Several things are configured in these devices:
- 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 proportional shift with 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 in setting up bicycle derailleurs.
Reaction to the rope
Many people have heard that derailleurs for bikes Shimano and SRAM. the leaders in the production of these devices. are not compatible. The reason for this is simple. their products use different Gear Ratios. If in SRAM it is 1: 1, i.e. When pulling the cable by 5 millimeters, the frame also moves by 5 millimeters, then in Shimano it is 2: 1, i.e. When the cable is displaced by 5 millimeters, the frame will move by 10 millimeters.
So far, there has not been a steady proof of the advantages of this or that system, but the versatility and interchangeability continues to suffer, including due to the emergence of new transmissions for 10-speed cassettes, which do not work with the shifter even of its title manufacturer.
Cable feed to switches
There are two ways to feed the cable. straight and traditional. The traditional way is to bypass the Dropouts. With a direct feed, the cable is attached to the switch from above and laid along the shortest path. Direct supply has its advantages. lower weight and no loop that can catch on an obstacle. A special adapter can be used to bring the cable directly to the switches with Traditional Cable Mount. Avid Rollamajic.
Traditional cable feed
Direct cable routing
Cable inlet through Awid Rollamajic adapter
The device and principle of operation of the rear derailleur
The rear derailleur is a gear shifting mechanism that allows you to move the chain, passed through its frame and rollers, along the stars of the rear cassette or ratchet. The chain is thrown by moving the switch along the axis of the cassette (ratchet), and the switch can also be moved in a vertical plane to maintain a constant distance from the rear sprockets to the roller.
A cable drive is most often used as a switch drive, less often hydraulic or electric. Moving from small stars to large ones is carried out by pulling the cable, and in the opposite direction by pulling the chain.
The speeds must be switched while pedaling, and at a light load. By adhering to this rule, the speeds will shift more clearly and the life of the switch will be maximized.
Rear derailleur device
The metal from which the switch is made affects not only the price, but also the weight of the structure, as well as strength. The cheapest are the rear derailleurs made entirely of steel alloy. The disadvantages of such switches are low strength and susceptibility to metal deformation. Steel derailleurs are used on lower end bikes. The most advanced switches are made from titanium and carbon fiber. The spring in these rear derailleurs is titanium and the frame is carbon. Something in between and the most popular is the aluminum alloy. Do not look at the fact that the switch is considered aluminum, some parts are still made of steel (Adjustment bolts, spring).
Rear Derailleur Mounting
There are two types of rear derailleurs on a bike, which are usually attached to the frame:
- Under the hook. the switch is attached to the bicycle hub. Such a mount is more reliable, but has a strong drawback. with a strong impact and breakage of the switch, the bushing also breaks, which entails high costs.
- Under the bolt. such switches are attached either to a special hole in the frame, or to or through the “cock”. Special adapter. The advantage of the rooster is that with a strong blow, neither the switch nor the switch breaks, but only the cock. The price of a rooster is incomparably small compared to a derailleur and bushing.
Bolt-on rear derailleur
Rear derailleur for hook
Mount holder (rooster) rear derailleur
Rear Derailleur Design Types
Sooner or later, the rear derailleur wears out and it becomes necessary to replace it. Then the question arises about the interchangeability of the rear derailleurs. Switches can be classified into types based on the following parameters:
- Switch frame length. this parameter is responsible for the so-called switch capacitance. That is, the length of the derailleur frame is responsible for the gear ratio range with which the rear derailleur can work. Simply put, the capacitance of a derailleur is the sum between the difference between the small and large stars of the cassette and the system. For example, if the cassette is 11-32T, and the system is 22-44T, then the required capacity can be calculated using the following formula. (32-11) (44-22) = 43T. 43T is the minimum allowable capacity of the rear derailleur. The numbers indicate the number of teeth of the stars.
- Spring Direction. Indicates in which direction the switching is performed by the spring. The most popular direction is Top normal, that is, switching by cable is carried out from a smaller star to a larger one. All rear derailleur manufacturers adhere to this principle. But there is also a reverse direction (Low normal), when the chain is dropped by a cable onto small stars, and switching to large stars is carried out by a spring. Rear derailleurs with this direction are only found in the Shimano range. These switches do not have significant advantages, and therefore did not gain popularity.
- The drive ratio is the ratio of cable movement to derailleur movement. This ratio can be 2: 1 (Shimano) or 1: 1 (Sram). It is these indicators that DO NOT allow the switches of THESE manufacturers to be interchangeable. It is worth noting that there is a difference in the clarity of gear shifting from this indicator, although Sram claims the opposite (in practice, there is no evidence).
The rear derailleur was invented by the Italian Tullia Campagnolo and was first used in 1950. Its main purpose is to switch the reverse speeds of the bike. Since the switching of speeds is carried out by transferring the chain from large stars to small ones and vice versa, the chain tension must also change. The rear derailleur is also responsible for the chain tension. The rear derailleur is controlled by a lever on the handlebars of the bicycle via a cable.
Rear derailleur rollers
In order to tension and guide the chain, two rollers are provided in the switch. a tensioner and a guide. The rollers are usually made of plastic and are consumables. Since they wear out quickly, they need to be replaced periodically. The more the roller is worn, the less precise the gear change will be. The idler and idler roller between are NOT interchangeable. In addition,s from different manufacturers are also NOT compatible.
Rear derailleur rollers
Rear derailleur protection
- Shadow Technology. Shimano patented technology. Switches based on this technology protrude much less when positioned on small sprockets. This arrangement increases the chances of survival of the switch and cock during a side fall.
- Safety frame. This is a steel frame that attaches to the bike frame and covers the derailleur. This method of protection also increases the chances of remaining intact cock and switches.
Rear derailleur protection
Bicycle automatic gearshift technology
Innovations are constantly entering our lives, they have also affected the bicycle, or rather the gear shifting systems. In order to understand what changes have occurred in this area, we tried to disclose in detail information about the types of shifting, as well as tell you about the new products, which the engineers have equipped a bicycle with automatic gear shifting.
Bicycle gear shifting principle
So, there are 2 types of gear shifting systems:
- New automatic;
- Conservative mechanical.
Mechanical works with a cable, a shifter and, in fact, the switch itself. Automatic shifting is carried out using planetary bushings, which are improved by automatic gearshift systems.
How the derailleur works on a bicycle
The bike transmission consists of the following components: Cassette. This is a part of the transmission located on the wheel and attached to it with the help of a hub. It consists of one gear or two or three gears of different sizes. They are also called “stars”.
Another part of the transmission is the “system” (also called chain drive). In addition to cassettes (these are stars or gears), it includes carriages on which moving parts rotate. connecting rods and chains. The latter link all the elements into one system. The chains are designed in such a way that they transmit the force for wheel spin with an efficiency of up to 98%.
Bicycle chains can be of different widths and have a greater or lesser distance between the knots (backs), that is, between the threads, the places around which the sections of the chain turn during its movement and which fasten the links.
Rear speed (gear) switch. Performs not only the function of gear shifting, but also regulates the chain tension (maintains it during shifting). Gear change is carried out by transferring the chain from one sprocket to another.
Front switch. Another speed switch (but no tension control function). The front derailleur is only available on bicycles with two or more sprockets in front. The device changes several parameters: cadence, angular speed, and also the torque of the bicycle wheel.
Shifters (shifters). These are special levers with the help of which (the cables are also involved) the cyclist regulates the gear change. They are usually mounted on the handlebars, the case and to the left of it. The cables are in a kind of protective devices. in shirts. rigid tubes, which are attached directly to the frame.
Gears are needed by the cyclist to regulate the effort applied to pedaling on different parts of the terrain: plain, ascent, descent. If a bicycle (for example, an older model with a small and large wheel, called a penny-farthing) has a fixed gear (one and only), then one pedal rotation will also spin the wheel one revolution.
In those bicycles that have a speed switch, it is possible to achieve an optimal cadence (cadence) with an adequate amount of effort. For mountain climbing, large stars (gears) at the back are used in combination with a small chainring. For flat terrain without wind, you can switch to a smaller rear gear.
Pros and cons
A plus of mechanics, of course, is reliability, and a minus can be attributed to the inconvenience of switching on the move. And also, do not forget about stressful moments when the ability to control is limited. These issues cause constant controversy among cycling enthusiasts.
Using an automatic transmission in bicycles is convenient and safe. It is reliable, easy to operate, does not require additional settings and maintenance.
There is only one conclusion here: everything is learned in comparison. Which type of gear shifting on your bike you choose is entirely up to you. Some of the cycling enthusiasts will choose automatic gear shifting, while some will remain with the mechanics forever.
- On the site
- In contact with
- Manufacturing material. Here are steel to carbon fiber. The entry-level models are equipped with steel, and not always of good quality, and plastic. In the right hands, these switches even work sometimes. Models of the middle category in most cases are made with the introduction of aluminum. The most expensive models can boast not only precision in work, but also titanium, carbon fiber or composite.
- Frame size. In theory, everything is simple. the longer the frame, the more gears you can choose. However, one cannot say so categorically, since someone will prefer a short frame, and not afraid of stones, while others are interested in greater comfort in switching. And everyone is right in their own way.
- Straight, when the drive wheel and pedals are attached directly, without the use of a chain system. This transmission is found on penny farthing, monocycles (with one wheel), tricycles for children.
- Cogwheel, which uses gears with teeth.
- Shaft, which uses shafts to transmit torque.
- Belt. Here belts are used, which, unlike chains, do not require lubrication.
- Hydraulic. Hydraulic system is used, not mechanical.
- In the form of a planetary hub, consisting of a large number of parts and resembling a car gearbox.
- Combined, which is a hybrid of two types of transmissions for a bicycle at once: external and internal (Planetary).
- Checking the cable tension (for better performance, you can provide a margin and relax it a little).
- Checking the operation of the cable and tightening the three screws (H, L, which means, respectively, “High” and “Low”, as well as the tension screw) so that the rollers located on both sides of the bicycle chain are exactly in line with the very big and with the smallest star.
- There is a rear derailleur (the chain almost does not fly off the sprockets, which is especially important off-road).
- The chain remains free of dirt.
- Combines with a foot brake.
- Gear change is carried out without the need for movement.
- Minimum of spare parts: front and rear sprockets and chain. Highest reliability on any bike model.
- Remains operational in case of falls and accidents.
- Your clothing stays clean as it is possible to put on full chain protection.
- Heavy, which is very important for professional competitions;
- High cost in comparison with classical switching systems;
- Difficulty in adjusting gear ratios (all speeds can be adjusted only by replacing the front and rear sprockets)
- Limiting the maximum torque;
- Absorbs large amounts of energy up to 10%.
- The sun gear located in the center and attached to the axle of the bicycle wheel.
- Planetary gears or satellites revolving around the first (the parts are so named because their position resembles the planets and the sun).
- Element, which is called “carrier”. It locks the previous elements together.
- Epicycle or epicyclic gear. It surrounds all the satellites and the central sun gear. It is she who rotates from the pedaling of the cyclist.
- Spline drive, holding together and transmitting torque from the wheel sprocket to the planetary hub mechanism.
- The hex bolt is unscrewed, which secures the cable to the parallelogram, and is released. The adjusting cuff, which is needed to fine-tune the cable length, must be fully tightened, both on the switch itself (not available in all models) and on the shifter on the handlebar.
- By turning screw H, it is necessary to ensure that the derailleur rollers are located on the same imaginary line with the smallest sprocket (the purpose of this procedure is to prevent the chain from falling off the smaller sprocket).
- The shifter must be switched to the largest number (so that the chain is on the small sprocket). After that, you need to tighten and secure the cable.
- After it is secured, switches the speed lever to 1. 1, on the system to the smallest sprocket, and on the cassette to the largest.
- Fastening the entire mechanism to the cock. This fastener is a hole that is designed to be bolted to the bike.
- The shirt stop adjusts the tension. The rope is pulled or weakened by it. It is in THESE places that dirt or corrosion forms, which negatively affects the switching process.
- The guide is in the form of a kind of lever from the chute, through the yak a cable passes to the fastening bolt. Some device designs may not have guides, so the cable is immediately fixed from the stop with a bolted connection.
- Fixing bolt for securing the cable.
- Adjusting screw for installing the guide roller.
- The parallelogram is a movable structural mechanism of the switching device, which, when displaced, moves the foot with rollers in the appropriate direction, while changing the speeds.
- Screws L and H. They are designed so that the chain does not fall off when changing speeds.
- The foot is a frame in which the rollers are placed for passing the chain.
- The guide roller is designed to guide the chain on the sprocket of the rear cassette. The main purpose of the device is a guide when changing speeds.
- Tensioner pulley to which the chain is connected from the front sprocket. Excessive chain slack is eliminated by this roller and spring.
- To change the speed mode, you need to press the steering wheel adjuster.
- This adjuster is connected to the rear gear with a steel cable.
- The second end of the cable is fixed with a parallelogram through a bolted connection.
- When the cable is pulled, the parallelogram is displaced towards the larger star. When weakening. in the opposite direction, that is, to a smaller star.
- When the cable is loosened, the movement to the smaller star of the parallelogram is provided by the spring.
- When the position of the parallelogram is changed, the presser foot is displaced in the desired direction together with the rollers: guiding and tensioning.
- The tensioner pulley is spring-biased, thereby eliminating chain slack. The accuracy of gear shifting depends on this mechanism.
- The guide roller moves the chain to the desired sprocket. The chain is fixed by small projections on the star.
- Now you need to adjust the position of the switch rollers with the screw L so that they become in line with the largest star.
- When the screw L is moved clockwise, the entire unit moves in the direction of the small star, and against it. in the direction of the rear wheel.
- You need to switch gears to 1. 1. On the system. to a small star on the cassette. to a large.
- Hitting the roller with the cassette in the process of engaging gears 1. 1, 1. 2 indicates the need to tighten the third screw (increase in tension). This screw adjusts the distance for trouble-free switching.
- It is recommended that the distance between the Tooth Tips of THESE two nearest stars be approximately 5 mm.
A bit of boring theory
The rear derailleur mechanism throws the chain over the cassette stars, allowing you to lower or higher gears (for reference, it was invented by the Italian Tullia Campagnolo back in 1950). This device also keeps the chain taut. There have been many varieties since the invention. A little about the main, most characteristic features.
You can still describe in detail the action of the spring or the options for the location of the cable for a long time. However, many good articles have been written on this topic. I will only note that there is not much difference from which side the cable enters the switch. So, now about the interesting.
Types of bike transmissions
A bike drivetrain can be:
Bike drivetrain setup
With regard to tuning the transmission of a bicycle, this extremely important part of caring for a bicycle during its operation, it is carried out in several stages:
The operation of the transmission of a bicycle is something that every cyclist should know, because the correction of emerging breakdowns, as well as the care of transmission elements and its adjustment are questions that every bicycle owner will have to face.
A novelty that delighted cycling enthusiasts.
Some time ago, automatic shifting bicycles began to appear on the market. They quickly won their loyal fans, as they solved the Essential issue: automatic inclusion of the desired gear in conditions of relief, physical and other restrictions. In situations where you need to quickly make decisions, automation has become indispensable.
Planetary hub components
The main feature of the automation device is a planetary hub with a built-in automatic transmission. This system is completed in one sealed mechanism from the gear, which is mounted inside the wheel. The device is quite reliable and does not require additional maintenance. It is well insulated from water and dust due to the design of the mechanism. And it is also worth noting the features of the transmission chain, which began to be made wider and stronger. Its main task is to transfer forces, and not for flexibility, as in conventional transmissions.
The main advantages of bushings are:
Disadvantages of planetary hubs:
The latest developments of new generation bushings were presented to your attention by several companies at once. In fact, these are automatic boxes, which are equipped with bushings.
Shimano and SRAM became the leaders in this industry, they were the first to improve the bicycle with automation. These simple devices are produced in small batches and work on the basis of electronic sensors Nexis, Shimano, Auto and the second.
Consider devices that are installed on a bicycle for automatic gear shifting.
The planetary hub (internal derailleur) is primarily used on conventional bicycles, not for special and non-standard loads. It consists of the following details:
Planetary bike hub device
How to set up and adjust the rear derailleur
Now let’s take a step-by-step look at how the rear derailleurs are adjusted on speed bikes. The setup procedure begins with preparation.
To adjust the mechanism in question, you must first make sure that there is no defect in the cock on the bike. If the cock has a Curvature, then it must be leveled or replaced with a new one. The most common causes of curvature of the cock are falling from a bicycle or extreme riding. You can visually make sure that the cock is even. If the rollers are not parallel to the cassette stars, then the cock is bent.
The second point of the preparatory process is that the quality of the shirts is checked. The shirts are often clogged with dirt, which negatively affects the operation of the cable. You can check the correct operation of the cable in the shirts manually, with little effort. If the cable in the shirts does not move, then the adjustment will be useless until the shirts are replaced.
The third point is the rear derailleur backlash. A strong parallelogram play requires replacement of the entire rear derailleur mechanism. All these checks must be performed even before the start of adjustment work.
If the cock is even, the cable runs freely in shirts and there is no play in the parallelogram, then you can begin to perform tuning work.
Features of adjusting the rear derailleur on a bicycle
High-speed bike owners face issues such as erratic gear changes, chain dropping off the sprockets, and inability to move the rear derailleur. During cycling, the occurrence of such situations brings a lot of inconvenience, so you should fix the problem as soon as possible. You can adjust the rear derailleur yourself.
How to adjust the high gear limiter
Screws L and H do NOT affect the adjustment process, they serve to prevent the chain from falling off the cassette stars. For the setup process to be successful, you need to position the chain on the largest chainring in the front, and on the smallest at the back. Then we carry out the following actions:
Clockwise rotation of the screw H contributes to the deflection of the frame towards the larger star in the radius, and against. to the smaller.
Design features and principle of operation of the device
The rear derailleur of different models (Shimano, Deore, Sram, SunRace, Acera, Tourney) has the same operating principle. The main components of the rear derailleurs on high-speed VELOBIKE are:
The design features of the rear units are identical and may differ only slightly. The photo above shows how all the structural elements look like. The operating principle of the rear derailleurs is as simple as the design.
This is how the rear speed changers are arranged on high-speed bicycles, with the exception of planetary ones. Mechanisms with 6,7,8,9,10 and 11 speed systems are now on the market, but the principle of operation is the same for all.
Features of adjusting low gear limiters
The purpose of screw L is to prevent the chain from flying off the largest sprocket in the cassette. If it is incorrectly adjusted, then during the shift, the chain can fly off, and build up between the spokes and the large sprocket. Before making the adjustment, the chain must be positioned as follows: on the rear cassette it should be on the largest star in the radius, and in the front on the small.
This completes the adjustment process. It remains to more accurately fine-tune the accuracy of gear shifting by rotating the cuff, and also check the chain tension.
How the rear derailleur works
The rear gearshift device is a mechanism by which the number of teeth of the driven gear is changed. Such a mechanism was invented back in 1950, and is intended so that the cyclist has the opportunity to facilitate movement.
When moving up, you need to switch to sprockets with a large number of teeth, and when driving on a flat road, you need to switch to stars of a smaller diameter. This will speed up the movement of the bike during cycling. Over time, any mechanism is characterized by a Riot of salesmen, so if it does not carry out regular adjustments, then serious repairs may soon be needed.
To adjust the rear derailleur, you need to follow the instructions, which can be found below. Compliance with this instruction will allow owners of high-speed bicycles to quickly adjust their vehicle so that it does not fail on the road.
What you need to do before setting up work
Before adjusting and adjusting the rear transfer, you need to inspect the rear sprockets for dirt and defects. If necessary, it is necessary to clean from dirt and lubricate all the components of the transmission mechanism. Sometimes it is enough to perform a cleaning to make the switch function again in the previous mode.
For cleaning the mechanism from dirt and working off, special cleaning fluids are used, which clean all the elements of the mechanism. The cable is checked for integrity and freedom of movement, which needs to be cleaned and lubricated, or replaced with a new one. The bicycle chain is also lubricated, which is described in detail in another article. The rear cassette and the front system are cleared of dirt and clogged, and only after that you can proceed to setting.
When all the preliminary measures have been taken, it remains to adjust the rear derailleur, for which there is an instruction.
Adjusting the chain tensioner
The tensioner provides a smooth jumping chain. Tensioning too tight will wear out the system, so you will need to check and, if necessary, adjust the tensioner position:
After following all the recommendations described above, the selection of the necessary gear when moving the bike should be smooth, without jamming and jumping off the sprockets. After completing the work, ride your bike, flip the switches, and, if necessary, additionally adjust the cable tension with the cuffs.