Front sprocket does not shift on a bicycle

Oval stars, different from round

Oval Star. New Or Retro Splash? We can say both. Experiments with the shape of gears for a chain drive (namely, giving it a flattened shape) began in the nineteenth century. Then it was somehow forgotten, and in recent years it has returned and is actively introduced into the modern cycling life.

The eccentricity of the star is slightly greater than zero, so the shape is close to a circle, by analogy with the Earth’s orbit. The maximum constriction can be up to 30%. They are not popular in our time, the release is more aimed at racing models.

The ellipse rotating around the axis redistributes the loads in its own way and changes the efficiency of the transfer moment.

Consider what are the features of ellipsoidal gears:

  • jumps in the gear ratio of the stars;
  • more even distribution of loads. a decrease in them with the horizontal position of the connecting rods and an increase in the vertical one;
  • overclocking is pronounced;
  • additional loads on the carriage shaft.

In accordance with this, we will analyze the pros and cons of such stars in comparison with round ones:

Benefits disadvantages
The bike will roll uphill faster Faster rear cassette wear
Better low cadence pedaling in high gears Increased load on the carriage
Acceleration by additional pushing torque (system) Need to pedal more often in low gears
Even distribution of muscle stress, less fatigue on flat areas
Easier to ride MTBs with powerful cushioning

An elliptical drivetrain pays off when you have to pedal at low cadence. Compared to the round counterpart, it provides some advantage in accelerating the bike from a standstill. There is also a change in the gear ratio without switching.

  • front. horizontally, back. vertically;
  • in front. vertically, driven. horizontally;
  • only horizontal position;
  • only vertical position;
  • deviation: for example, the leading sprocket is strictly vertical, and the rear sprocket is at an angle from a straight line.

Thus, the oval system and cassette leave prints of fundamental differences on the bike: both in appearance and in ride quality.

Gear ratio of leading and driven stars

The sprockets on high-speed bikes are located on the right crank arm (driving) and the rear wheel hub (driven). Through the chain, there is a transfer of forces from the front gears to the rear. Interestingly, the rear wheel, on the contrary, is the driving wheel, and the front wheel is driven.

Gear ratio is the difference between the size and the number of teeth on the stars. This parameter directly affects the travel speed and transmission power. A high gear ratio is provided by a large drive and small driven gears, a low gear ratio, on the contrary, by a small front sprocket and a large rear sprocket. Accordingly, the gears on the classic transmission in the first case are 3 x 8, and in the second 1 x 1.

The larger the chainring, the higher the speed. For example, there are 44 teeth on the front for the chain engagement, and on the back there are 11 teeth. For one revolution of the pedals, the rear gear will make 4 revolutions. If we take gear 22 to 11, then only 2 wheel revolutions will be made here per pedal rotation. At low gears, the opposite situation is observed: in front of the chain stands on a 22-gear gear, and at the back on 32. The gear ratio is less than 1, that is, for 1 revolution of the pedals, the wheels do not have time to turn completely.

High gears are designed for fast travel on a flat road. On hills, in headwinds and in poor road conditions, lower gears are used. the bike speed is lower, but the power is higher and the energy consumption is less. Medium star ratios such as 2 x 5 and 2 x 6 are often used.

Each star in the system has its own range on the cassette. It can “float”, that is, the same reverse gear refers to two stars of the system at once, but, in principle, the pattern is as follows:

What do we have for single speed bikes? There are only a couple of gears, a classic gear ratio of 2. Corresponds to the average performance on high-speed models, intended for movement on asphalt, compacted soils, conditionally acceptable on short climbs.

You can increase the speed of a single speed bike yourself if you put a larger diameter sprocket in front. For frequent overcoming of slides, it will be more relevant to increase the size of the rear gear.

And finally, how the programs are numbered. In the system, the asterisks are arranged in descending order, on cassettes. in ascending order. The outermost gears are the highest gears, the inner ones are the lowest. The smaller chainring corresponds to the first gear in the cassette, the last gear. According to the number of stars in front and behind, the gearing of the transmission is determined, for this we multiply the numbers:

  • 1 x 7 = 7 gears;
  • 3 x 7 = 21 gears;
  • 3 x 8 = 24 gears;
  • 3 x 9 = 27 gears.

Etc. Do you need so many “speeds” in practice? It all depends on the riding style and the area of ​​use of the bike. However, it is important to choose the right sprockets. this way they and the chain will be subject to less wear and tear, and the trip will be more comfortable. And if the transmission allows you to select the gear with maximum accuracy, then this is how it should be done.

Bicycle sprockets

Sprockets are transmission units for the implementation of a chain transfer of forces from the cyclist’s legs to the rear wheel. Bicycle sprockets play a paramount role. without them, it simply will not go. Single speed models are supplied with a pair of leading and driven stars. Bicycles with multi-speed transmissions are equipped with speed kits front (system) and rear. ratchet or cassette.

The number and size of the sprockets determine the bike’s flexibility in various road conditions. Thanks to the correct gear ratio, you can significantly reduce the energy consumption for the trip and move at a comfortable speed. The durability of parts depends on the quality of the material, the riding style and the quality of service. with proper care, even the “initial” stars will ride longer than professional, but neglected ones.

Types of fastening stars on a cassette

Let’s go back to the classic round cassettes. Unlike ratchets, they differ in the type of attachment to the drums. Bicycle cassettes are:

  • collapsible on a single drum with separators;
  • on a spider;
  • on blocks (several spiders);
  • Open-Glide;
  • X-Dome.

The first type of cassette is the simplest. all the stars are installed on a single spline drum. They are separated from each other by partitions. spacers. The disadvantage is the constant load on the drum. But the indisputable advantage is that they are easy to disassemble and change one asterisk. They are easy to clean, but the components are more likely to get dirty.

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Spider. Lite version of the collapsible cassette. The load on the drum is not so great. here it does not come from every star, but only from the spline mount of the spider. These cassettes are lighter, less likely to get dirty.

The multi-spider design includes multiple pairs plus small stars individually attached to the drum. The model is very convenient because the new block is easy to pick up and, unlike the collapsible analogue, you don’t have to fiddle with spacers for a long time and lay out the entire cassette. The development of this thing belongs to the Japanese manufacturer of parts Shimano.

The Open Glide is a one-piece set that fits onto the largest gear. Unpretentious model: thanks to high-quality material, less wear and tear, long service life, low weight. True, cleaning a heavily soiled cassette is problematic.

The X-Dome system is represented by a similar design. Here both the big and the small stars are in contact with the drum. A solid-milled block of 7-8 stars is mounted on them. Both Open-Glide and X-Dome are SRAM.

How to clean and lubricate sprockets

Rubbing mechanisms require periodic lubrication and cleaning from dirt. This will improve ride quality and extend the life of the transmission. Chain guards are often included with classic single-speed models. It is recommended to leave it. It also protects the chainring from excess dirt.

Already after a few rides through forests, cross-country and off-road, the mountain bike is overgrown with mud. And if it is clearly visible on wheels and frame, then in mechanisms it is not always. Therefore, more often you need to inspect your two-wheeled horse and take action in time.

Cleaning the bike cassette:
1. Release the rim brake (remove the caliper on the disc brake), remove the rear wheel.

Inspect for dirt. If everything is very bad, you will have to remove and disassemble the cassette. For light dirt, can be cleaned directly on the wheel.

For cleaning, it is better to use special narrow brushes. They allow you to crawl into the deep gaps between the gears and find a lot of interesting things there. And it is much more convenient than getting into the gaps with a rag.

You can clean the teeth with an old toothbrush or wipe off the abrasive with a soft cloth.

After that, wipe the surfaces with kerosene, allow to dry and apply grease to the teeth and pits. It is recommended to clean and lubricate the chain at the same time as the cassette. This is the only way to achieve the desired result.

Cleaning the system is done by analogy. Everything is simpler here: you don’t need to remove the wheel, just a few stars. True, you need to work carefully so as not to damage or upset the switch.

Sprockets are the most important components of the transmission, without which movement is impossible in principle. Correct selection of gears, periodic cleaning and timely replacement of worn components will avoid unpleasant surprises on the road, and a high-speed bike will really be high-speed, and not only ride in one gear.

Bicycle front derailleur

The transition to the setting of this mechanism is possible only when the rear derailleur is set. This is important for Honor before starting work. The figure shows the switch (round, black).

Leave the chain on the middle sprocket of the front block and place it on the large sprocket in the rear block. If chain friction is observed, re-engage adjuster L. To adjust stop H, the chain moves to the largest sprocket at the front and smallest at the back. The adjuster will help to position the chain in the optimal position without friction and excessive tension on the chain. At the end of the work, be sure to check the quality of its implementation.

Rear derailleur

Make sure the cock is level first. If it is still bent, you can contact the service to straighten it, or try it yourself. Alternatively, you can simply replace it. For 2016, for roosters are only about 300-900 rubles. Do not even try to tune the derailleur with a bent cock, as the gear setting on the bike in this case will not work for you.!

Some firms produce the so-called cock guard, which is attached to the frame. Do not buy it under any circumstances! A rooster is a consumable component that can and should be replaced if it breaks. When hitting this very protection, the cock will remain intact, but the frame may crack. The frame is harder and more expensive to change.

Front Derailleur. Advanced Troubleshooting

When you are convinced that the rooster and the cable are in good condition, you can proceed to the actual setting.

Place the chain on the largest chainring in the front and the smallest in the back.

Unscrew the bolt that holds the rear crossover cable.

By rotating the bolt with the inscription “H” you need to make sure that the switch rollers lie in the same plane with the desired sprocket.

Then lightly stretch the cable and tighten the bolt holding it. Over-tensioning the cable will make the crossover difficult to work.

Shift the speed to the lowest (i.e. the largest star in the back and smallest in the front).

Rotate screw “L” until the derailleur rollers line up against the large sprocket.

Check if gear changes are good.

If shifting is not correct, use the thumbscrew on the shifter, which changes the cable tension.

Now that you have set up the rear derailleur, you are ready to adjust the front.

Reasons for incorrect gear shifting

Many people may face some difficulties when setting up switches. First, a little theory. The front derailleur does not work by itself. It works in conjunction with the stars of the system.

Front derailleur not shifting to big ring

There are special nodules on the stars, which are designed to make the chain switch better. The quality of switching directly depends on the state of these “pins”. If they wear out or wear out, then accordingly switching will suffer very much.

The front derailleur itself consists of the following components:

The frame comes in different thicknesses. Internal width depends on chain width.

  • You also need to pay attention to backlash.

Bicycle Speed ​​Switch Adjustment Instructions

Usually, advanced cyclists change the derailleurs to fit their bike exactly the equipment they want, thus adjusting the bike to their needs. Beginners usually do not have to think about such an acquisition, unless a breakdown has occurred. Nevertheless, it will be useful to consider popular models.

The first models were invented in the 50s. In essence, the gear system is the front sprocket. The chain is thrown from one chainring to another, increasing or decreasing the cadence.

  • Fast pedaling at low speed. low gear. Combination of large front and back sprockets. It is designed to overcome mountains, off-road and similar areas.
  • Increased for high speeds. It is a large star in the front and a small star in the back.

Switching takes place using a derailer:

  • The rudder coins pull the cable.
  • The frame shifts and throws the chain onto an adjacent star.
  • The back is the same. The patch moves from the tension of the cable and throws the chain.
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Now you know how it works. There are two main product manufacturing companies:

On the steering wheel, gears are measured using coins:

front, sprocket, does, shift, bicycle
  • A switch combined with a handle. To change the speed, you just need to turn the drum to the desired mark indicating the gear. They are easy to use, which is why they are often used on children’s and women’s models.
  • Triggers. They control the change in the position of the cable using two levers. They can be combined with the brake lever, or they can be installed separately. This combination is usually found on advanced models with a hydraulic braking system.
  • There are high-end combo handles. Such a brake lever can be shifted from left to right, thus changing the gear. Analogs have been around for a long time on road bikes.

How the switches work

Using the handle and shifter, the cyclist activates the required speed. In a certain position of the handle, the cable is pulled. As a result of this tension, the frame is thrown onto larger sprockets; when the cable is loosened, it is not thrown onto small sprockets. As mentioned above, you can start setting up your bike from the rear derailleur. Procedure for adjusting the rear derailleur:

  • select the second star in the front block, and the smallest in the rear one and set the switch chain on them;
  • The bike’s rear derailleur system has two bolts that act as stops. One is abbreviated as H, and on the other. L. These two bolts are used to adjust the high and low gears on the sprockets. If during the adjustment process any extraneous sounds occur, you can get rid of them with the help of the latch;
  • check the tension of the cable and if the tension does not correspond to the required one, use the regulator located on the shifter;
  • Test the switching quality. If the switching occurs smoothly, no extraneous sounds are heard, then you did everything right.

Rear derailleur

The gear selector is an important part of a multi-speed bike. Thanks to this component, it becomes possible to move in extreme conditions, which include movement against the wind, ascents, poor road quality. The transmission unit must cope with all these problems. The quality of the ride and the safety of the cyclist depend on the smooth operation of the speed switch. This skill is very useful, and every bike owner should learn how to independently adjust the gear shifter. Each cyclist can make adjustments to the bike’s gear shifters on their own. You need to study the theory in detail by reading the instructions, or using the advice of experienced bike owners.

Before setting the derailleur, the rear derailleur must be adjusted. Placing the bike in the correct position (wheels up) will greatly facilitate the entire adjustment process. So, all the necessary details will be in sight, and it will be much easier to get to them.

Reasons for poor gear shifting:

  • physical defects of the switch parts;
  • contamination of parts. To prevent this from happening, the components of the transmission unit must be periodically cleaned of dirt, dust and old grease;
  • worn out cable with elements of damage. Such a part requires replacement;
  • damage to the cock.

If you observe damage, deformation and wear of the constituent parts, they must be replaced as they are practically irreparable.

If all parts are OK, adjust the switch. What is the speed selector made of? The components of the speed switch are as follows:

  • The handle for shifting the speeds, located on the steering wheel;
  • A shifter that attaches to the handlebars near the handles. Handles and a cable are attached to the shifter. It is with the participation of the cable that the impulse is transmitted from the shifter to the stars;
  • Cassette, which includes stars of different sizes;
  • front fixing mount;
  • rear derailleur, whose main function is to transfer the chain to the necessary sprockets.

Bicycle does not shift gears

Front crossover

It is important to set it up especially accurately, since if the adjustment is not good enough when switching speeds, the chain can fly off or even break. The sequence of your actions will be as follows:

Use the rear shifter to shift to the middle sprocket so that the chain is not too skewed.

Next, put the chain in first gear and unscrew the bolt securing the cable.

Use the screw “L” to move the transfer frame so that the distance from the chain to the switch on the left and right coincides.

Without too much tension, place the cable and secure with the bolt.

Switch to the biggest star in the front.

Tighten the screw “H” so that the chain is again exactly in the middle of the frame.

Check adjustment results and achieve maximum shifting accuracy with the thumb on the shifter.

If the shifter triggers are too tight, loosen the cable tension.

How oval stars differ from round ones

The ellipse, rotating along the axis, distributes the load differently, which causes changes in the transmission moment. Although the principle of operation may not be clear in appearance, there are still differences from the circle, and here are some of them:

  • In motion, there are drops in the gear ratio;
  • Loads are delivered alternately. So, when the ellipse is scrolled to a horizontal position, the load decreases, while when it is vertical, it increases again.
  • You can reach high speed faster, and this is noticeable when you need to cover distances as soon as possible.
  • Additional loads are applied to the carriage shaft.

The comparative table shows the disadvantages and advantages of ellipse-shaped stars for a bicycle.

As you can see, there are differences between the oval and round shapes. It is important to understand the purpose of installing one type of sprocket or another. After all, driven gears can also be flattened, and this promises certain opportunities for professional cyclists. We figured out the forms, it’s time to shed some light on the fastening methods.

Chainrings for bike

The principle of a bicycle is understandable to everyone who has ever tried to ride it or seen how others do it. The chainring is the driving mechanism for converting the pedaling energy and transferring it to the rear (driven) chainring that drives the wheel. In other words, whether the bike will move at all depends on the correct operation of this unit. But as in everything, one should “get to know” the stars better in order to understand the principles of work, and most importantly the rules of choice.

First of all, stars should be classified into two types: beginner and professional. The first ones are more common, since their cost is lower, and there are fewer functional features. Alas, the story is the same with the quality of the material: on cheap models of the front (as well as the rear) sprockets, the teeth often fail. This is not surprising, because the load required to drive the rear wheel is not small, but a cheap metal or alloy is either soft (then the teeth are deformed, and the sprocket bends), or brittle. Consider the principle of operation and transfer of energy from the chainring to the rear.

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Types of fixing stars on a cassette

Returning to standard, round cassettes, it should be noted that they differ from ratchets in that they can be mounted on drums in different ways. Thus, it is possible to conditionally divide bicycle cassettes into such types as:

  • Collapsible, on a single drum with separators. The name of this type of fastening already gives a hint about the method of fixing the stars: they are all fixed on a single drum, and between them, as partitions, there are spacers that ensure there is no interaction between adjacent gears. This type of fixation has both advantages and disadvantages. So, with frequent clogging of the star, you can easily disassemble and clean, replace one or more gears, if necessary. But at the same time, the constant load on the drum must not be overlooked.
  • On a spider. This method of fixing is more often used on bicycles in order to reduce the overall weight of the structure. The photo shows exactly how the stars are attached.
  • On several spiders. The design is quite interesting, as it is attached not only to several spiders in pairs, but at the same time small stars are fixed separately on the drum. This assembly method allows you to quickly deal with sudden difficulties, the need for cleaning or disassembly.
  • Another unique type of fixation is called Open-Glide. It involves fixing a set of sprockets to one large gear. On the positive side, Honor is replaceable and durable, as well as lightweight. But not every lover can afford the price.
  • The X-Dome differs little from its predecessor in the type of attachment and appearance. differences are in the company, or rather the name.

The ease of maintenance largely depends on the type of fastening. So, we can conclude that the simplest option is still the first. Yes, a drum in a collapsible type of mount suffers from increased load, but at the same time, with moderate driving, it is used for quite a long time, and the replacement of parts is elementary.

Gear numbering

In the system, the asterisks are arranged in descending order, on cassettes. in ascending order. If it is necessary to switch to high-speed mode, it is necessary to move the chain to the position of the outermost outer stars. The maximum lowered position. the leading one is the smallest, and the driven one is the largest. The rule for counting transmission steps is as follows:

  • 1 rear X 7 front = Seven-speed transmission;
  • 3 rear X 7 front = 21 steps;
  • 3 x 8 = 24 gears and so on.

Those. we simply multiply the number of rear stars by the number of front ones and the result will be the number of transmission steps (the number of speed combinations that are available to you). It is difficult to overestimate the importance of the ability of the transmission to accurately select the speed required in a given situation. Therefore, the higher the speeds, the lower the load on the chain, and the more durable the teeth and the sprockets themselves.

What it looks like in practice

The larger the diameter, the greater the number of teeth on the sprocket. An example of a high gear ratio (more effort, but higher speed) is the following ratio: front 44 teeth, rear 11. With this combination, it is quite difficult to pedal, but the travel speed will be high. This is especially true on the move, i.e. when switching speeds, already accelerating. It is quite difficult to gain acceleration at 44X11, and therefore, as a rule, they start driving with a combination of 22 front 32 teeth at the rear. In this situation, pedaling will be easy enough, but the efficiency of each revolution is much lower. The combinations essentially determine the gears: high. smooth road and high speed, low. when driving against the wind, on a bump, at a walking pace on an uneven road surface.

The figure above conventionally indicates the optimal ratio of gears for different driving modes. So, from left to right in the order of lowering the speed limit. If we mention that there are not only many, but also single-speed models (of which there are not few), then the mode characteristic of them should be designated (in the middle of the figure). This mode is considered medium-speed, in other words, universal. With such a transmission, the efforts are evenly correlated with the wheel revolutions and the speed gain.

Naturally, it is quite difficult to move around on a single-speed bike on the uphills. Indeed, in fact, they are intended for driving on rolled dirt roads, tracks with a flat surface. When climbing bumps (especially large ones), it is quite difficult to pedal, a lot of energy is expended. But there is a way out of this situation: independent selection of the rear and front sprockets. Those. we choose a large driven model and a small leading model and you can even travel through the mountains.

Gear ratio of front and rear sprockets

Each person has repeatedly seen where the stars are located on the bicycle: the front one is on the crank rod on the right, the rear one is on the wheel hub. The front sprocket is considered the leading one, since it is through its actuation that energy is supplied to the driven one. An interesting fact: the rear wheel, according to the same principle, becomes the leading one, in relation to the front. This is due to the fact that the front wheel, in fact, performs only a passive transformation of the received energy, and the efforts fall on the rear.

The gear ratio should be understood as a difference that can be traced in such parameters as size, number of teeth. The large diameter front sprocket in combination with the small rear circle increases the gear ratio. If the rear sprocket is large and the front sprocket is smaller, then the gear ratio will be lower. The amount of effort a cyclist makes with different combinations of these important elements will also vary. So, the larger the rear sprocket, the less load on the legs in motion and vice versa. Therefore, speed lovers need to install a large leading and small, driven stars.

Cleaning and lubricating sprockets

Both the chainring and the rear sprocket are subject to contamination. The lubricant used on the chain leaves its mark, and dust accumulates at the joints of the teeth and links. Thus, if the cleaning is not carried out for a long time, the sprockets become contaminated with deposits of dust and oil. In part, this process is slowed down on single-speed bicycles where chain guards are provided. It is presented in the form of a casing made of plastic, metal, alloys. Its use is recommended not only in order to protect the chain from contamination, but also to prevent the appearance of plaque on the sprocket.

To clean the sprocket, it is recommended to remove it (or them, if we are talking about a cassette). Thoroughly clean the surface with fine-grained emery paper, and then lubricate with profile oil (many use grease, Litol, and so on). Reinsert the stars and continue to enjoy your favorite destinations!