The Chain Falls Off On The Bike What To Do

Weak chain tension in bicycles without gears

The rear fork of a conventional bicycle, without shifting speeds, under the influence of loads and vibration, changes the position of the shaft along the axis of the rear hub. Chain drive slack increases. A slight push releases the chain from the sprocket teeth. The chain slips off. To fix the problem, you need to follow the steps in sequence:

  • Upside down bike.
  • Loosen tensioning bolts.
  • Will settle the wheel to the required depth.
  • Tighten the bolts hard in the new location.

The Chain Falls Off On The Bike What To Do

Cycling will be fun and the chain will not go off anymore if you fit the wheel properly. Correct position implies:

  • Lowering the chain by about 5 mm. the state “in line” makes it difficult to pedal;
  • Here the rear wheel hub should be perpendicular to the plane of the frame. Otherwise, the risk of deformation of the rim increases;

To improve the grip of the nuts, use lock washers.

If in the extreme position of the sprocket critical slack is NOT eliminated, you need to rivet the links to reduce the chain length.

Why can a chain on a bicycle come off. an overview of the causes and their elimination

Thousands of new members are added to the cyclist army every year. Novice owners often do not know what causes the chain on a bicycle to fly off and what to do in such situations. Let’s consider the main causes of the problem.

Insufficient chain tension in shifter bikes

Often the reason why the chain flies on a high-speed bike lies in the failure of the compensating springs to perform the functions to prevent sagging. Occurs when the spring is loose or the chain is stretched. If the test shows excessive chain elongation, you need to remove the extra links. A weakened spring cannot be repaired, you will have to change the rear gearshift block.

Adjustable by bolts with indexes “H” or “L”.

  • The chain does NOT fly off the rear wheel cassette if the derailleur sprockets are in the same plane as the largest or smallest sprocket in the cassette. Bolt “H” changes the alignment with the smallest, and bolt “L” with the largest diameter stars.
  • For the front wheel, bolts “H” or “L” set the gap between the teeth of the stars and the walls of the front derailleur frame equal to one millimeter. A knob with the letter “L” sets the gap between the largest star and the inner wall of the frame, and with the letter “H”. between the smallest star and the outer side of the limiter.

You need to carry out the action with the gearshift unit with the setting on the shifter of the speed mode corresponding to the selected star.

Damage to SEPARATE bike parts

Sometimes the chain on a bicycle flies off when the teeth are deformed from a blow or fall. In such cases, it is very difficult to return the teeth to their previous position on their own. Depending on the mounting of the stars on the cassette, a separate damaged star or the entire block changes.

Violation of the geometry of the bike frame or wheel (figure eight) can lead to imbalance and slipping of the chain from the star.

The cause of the breakdown is a change in the direction of the carriage and bushing axes. As a result, the chain links do not fit tightly enough to the teeth of the sprocket and easily jump off. An additional negative manifestation of deformation of SEPARATE parts of the bicycle is accelerated wear of moving parts.

A minor figure eight can be corrected at home by loosening or tightening the knitting needles. Riding with a warped wheel is possible, but you should remember that a rock or pothole increases the figure eight and the chance that the chain will come off on the bike. It is best to contact the Repair Shop, where they will explain to you why the chain on the bike flies and solve the problem with the breakdown.

Speed ​​bike problem

For a regular bike, this problem is easy to solve, but what if the chain jumps off on a high-speed bike? Among the most common causes of this problem are the following:

  • Deformation of one of the stars. Gear shifting on multi-speed bicycles is carried out using cassettes consisting of several stars. These designs are collapsible and non-collapsible. Replacement of a damaged star is possible only in collapsible structures, if the structure is non-collapsible, its complete replacement is required.
  • Mistakes in the derailleur setting can cause the chain to fly off the bike when shifting gears. Gear shifting should be fine-tuned. If the bike owner himself cannot do this, you need to contact a specialist, or carefully study the instructions for setting the bike speed switch. The safety of the cyclist depends on the quality of this function.
  • Stretching the bicycle chain. This process is associated with long-term introduction of the chain, the application of high dynamic loads to it, irregular cleaning, due to which the residues of lubricants accumulate on the chain links mixed with dirt and dust. In this case, the chain must be shortened or replaced. To shorten the chain, you need to remove several links from it. This is done using a special squeeze tool. This simple tool is a must-have for every cyclist. With its help, a link (pin) is pushed into a lockless type bicycle chain. If there is noticeable stretching on the bicycle chain, and the service life is long, it will be more expedient to replace it completely. To keep the chain in good condition, it must be periodically rinsed in kerosene and cleaned.
  • The curvature of SEPARATE chain links, as a result of which the chain flies off the bike.
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A new chain slips

It would be nice to replace the cassette. If the previous chain did not dance over the stars, then you can leave everything as it is. the “novye” will roll in and the smoothness of the course will be restored. Depending on the degree of “stretching” of the teeth, running-in will take from 50 to 150 km.

Attention! Don’t forget to inspect the system sprockets and ratchets. Please note that you left everything as it is, the chain resource in km will be lower.

The chain is stretched due to prolonged use

This happens in the process of wear and tear. The switch spring cannot tighten it normally, it constantly sags. In this case, there is only one way out. to replace the circuit with a new one. In practice, it is rare to find bicycles in which the chain is stretched and jumps when shifting gears. To restore its elasticity It is virtually impossible.

Educational program

If you create ideal working conditions for the axles of the links of the bicycle, then the components of the chain drive can go for years. about 10,000 km without any intervention. It is still possible to guarantee the absence of distortions, but it is difficult to ensure surgical cleanliness and the constant presence of grease in the roller-pin contact patch.

Note. The experience of operating Shimano chain is about 10,000 km instead of the usual 1,500 km. To reach this level, it is necessary after each ride to clean all the links with a kerosene-containing preparation, for example, WD-40, and lubricate with a dust-repellent bicycle lubricant. Well, distortions, of course, are unacceptable.

Deformation of one or more teeth in the chainring or chainring

Why can teeth warp? The first obvious reason is due to impact, the second is due to severe wear. In any case, if the chain falls off solely due to problems with the cassette teeth, then it must be replaced with another one.

Rear wheel deformation

Perhaps the problem is the deformation of the rear wheel. One of the most unpleasant cyclist problems is the so-called “eight”. “Eight” is the deformation of the wheel, violation of its shape and the inability to perform functions. This problem is eliminated by tightening and loosening the spokes with a special spoke wrench. To do this, the wheel is removed, the affected area is determined and the central spoke of the “eight” is highlighted. Then the needles are pulled through one.

Why Mountain Bike Chain Can Slip Under Load

There are, in fact, only two reasons. The rear derailleur is incorrectly adjusted or the chain and sprockets of the system and / or cassettes are worn out.

Now how to put the chain on a single-speed bike in place.

The idea is this: First, it is completely put on one of the stars (usually on the back, but you can also on the front) and thrown over the second sprocket (front or, respectively, back) so that they lie on the part of the teeth. Further, when scrolling the pedals in the direction of travel, the chain is captured by the remaining teeth of the sprocket and completely lies on the entire sprocket and is thus put on.

How to put a loose chain on a bicycle

Not long ago, a child’s chain fell off while riding a single-speed bike. On a bike like this, this is a serious problem. Neither drive forward nor brake. It’s still good if the wheel is not jammed.

This is why an additional front V-brake is required on single speed bikes. At the very least, it will always help you brake in an emergency with a bicycle chain.

I told him on the phone how to put it back. It seemed to work out, I came home, they began to understand and eliminated the very reason that led to this. I decided to describe everything, since this problem often arises, and sometimes it has to be solved in the field.

First of all, you need to understand: why it flies.

What to do if the chain slips?

If the chain slips on the bike without gears, it is enough:

  • Unscrew the nuts in the area of ​​the rear wheel axles;
  • Pull the wheel towards you;
  • Tighten the nuts, control the immobility of the wheel to the center of the frame.

Sprocket wear

The stars can deform due to wear or mechanical damage resulting from impact. In both the first and second situations, it is impossible to restore the cassette teeth. Then you need to replace it with a new one.


There are a number of reasons why the chain fails. They are listed below:

  • Weak tension (applies to both bicycles without gears and with variable transmission)
  • Curvature of one or more links;
  • Deformation of one or more teeth in the chainring or chainring;
  • The chain is stretched due to prolonged use;
  • Front or rear derailleur incorrectly configured.

Now let’s take a closer look at each problem. Here we also offer solutions to emerging difficulties.

Insufficient tension

If you have a bike without gears, first unscrew the nuts on the rear wheel, there are two of them, pull the wheel towards you. Next, return the nuts back, so as to exclude the displacement of the wheel to the center. That’s all there is to it. It will be more difficult to fix this problem in the unit with speeds. There is a spring in the gear derailleur of a high-speed bike, which independently tightens the chain, over time it stretches, in which case you need to change the derailleur.

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Both factors at the same time

Also, the chain can slip due to the stretched chain and wear of the sprockets at the same time. This pattern is due to the following: as the distance between the chain rollers decreases, the sprocket teeth also narrow. To determine the degree of wear, it is enough to compare the width of new and worn views.

The reason for the one-time wear of the chain and sprockets is also incorrect gear shifting. This leads to a strong distortion of the chain, and some parts of the parts are under increased pressure, and they wear out faster.

Weak tension

If your chain flies on a bike without gears, all that is needed is to unscrew the two nuts on the rear wheel axle, and then pull it towards you.

Tighten the nuts, but make sure that the wheel does not move closer to the center of the frame. After completing these steps, you will see that the chain will not sag. Accordingly, the likelihood that it flies again is completely excluded. But in the case of this problem, on a high-speed bike you will have to sweat. A special spring is installed in the gear selector, which automatically pulls the chain. With prolonged use, it loses its elasticity, which leads to similar problems. Since the transmission is not separable, you will have to change the switch to a new one.

Stretched chain

The most common cause is chain stretching due to long-term use of the bike, which causes the chain components to wear out. The main indicator of chain wear is its length (normally it is 304.8mm).

As a result, the spring on the derailleur does NOT tension the chain. This contributes to chain sagging and a decrease in the quality of gear shifting (which is especially noticeable when changing from low to high speeds).

It is almost impossible to restore the elasticity of a worn part. After that, there is only one way to solve the situation. replacing the chain.

Measuring chain stretch

Stretching the chain does NOT imply lengthening, it occurs when the links are worn, due to which the distance between them increases, and the chain wears out. There is some discrepancy in the pitch between the sprockets and the length of the chain link in the worn part. As a result, the cassette and the entire transmission system do not work properly.

To determine the degree of wear, you will need:

Based on the results obtained, they understand how necessary a chain replacement is:

  • 30cm 48mm. new chain condition;
  • 30cm 48mm to 30cm 64mm is normal length;
  • From 30cm 64mm to 30cm 79mm. the length indicating the chain is worn out, replacement is required, otherwise the first problems with the transmission will appear;
  • Over 30cm 79mm. critical stretching, in such a situation, replacement of both the chain and the cassette (or sprockets) is most often required.

With a stretch of 30.8cm, the ride becomes unbearable. The chain either gets stuck or slips and dangles. Some use a squeeze to shorten the chain by a couple of links, but this does not help to solve the problem for a long time, and as a result they come to the decision to replace parts.

“Chain damper

To eliminate the risk of chain falling off the stars, cyclists install a Silencer. They can be equipped with rockring. special parts made of plastic to protect them from impacts while passing obstacles. curbs, pits, etc.

How they are installed ISCG calming agent:

  • Prepare tools: hexagons, squeezers, carriage pullers, threaded clamps, keys for removing bonds and grease;
  • Remove the stars and connecting rods so that the large star is set to the middle one;
  • Screw on the rockring;
  • The optimal position of the roller is selected (with a 6-inch suspension travel, the position is strictly at 12 o’clock, with a smaller one. at 11:30)
  • Tighten the bolts;
  • Threaded fasteners drip in the area of ​​the mounting bolts;
  • Install connecting rods;
  • They put the stars on the chain;
  • The rollers are attached;
  • Align the distance between the inner pancake and the star so that it is identical to the distance between the outer pancake and the star;
  • The chain is not required to touch the pancakes;
  • After tightening the bolts all the way.

Why does the chain jump off on a bicycle?

The bicycle chain often jumps off completely at an unpredictable moment, however, some dynamics of this process is available for analysis.

  • On all types of bicycles, the chain will jump off when it is too long. In theory, the bike should have the correct chain length by default. But during operation, the chain stretches. Such a chain is no longer able to hold its position.
  • On high-speed bikes, the chain will jump off when there is a problem in setting the derailleurs or the derailleur foot is so worn out that it is NOT able to pull the chain with the required force. If the setting is lost, then the switch sometimes tries to throw the chain to the next gear and if at this moment the chain is not “lies on the star “completely, then it will jump off.
  • Incorrectly constructed system. If you have chosen the wrong components, then such problems are quite predictable. For example, a carriage with a too long axle was bought and, as a result, the system protrudes very far from the frame. In this case, the so-called chainline is broken. Due to such a skew, the chain flies and wears out quickly.
  • Extreme skiing and untuned shifting system. If you suddenly want to Bike on a bike, and you have NOT done anything with the transmission, then be prepared to periodically lose the chain on the go. To properly adapt the shifting system, add a chain damper to it, remove two of the three stars on the system and shorten the chain.
  • High wear of mechanisms and ingress of dirt / branches. This point is suppressed with point 1 and point 2, but differs in that in this case we are talking about excessive wear. In addition, we will also remember about excessive pollution. the cassette can collect so much debris, grass and branches that the chains will simply have nothing to catch on to. Often this point is determined by the slippage of the chain on the cassette. The torsional force is so high that a worn tooth is no longer capable of engaging the chain roller so tightly.
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The chain on the bike jumps off. Why is it dangerous?

If the chain comes off the bike, it can lead to a number of dangers. To begin with, if you are still using an old type bicycle with a brake sleeve, then if you lose the chain, you are left without brakes. The chain jumps off at inopportune moments when there is a lot of shaking or a lot of acceleration. As a rule, these are the moments when the cyclist flies downhill. Accordingly, the loss of brakes is very undesirable here.

If, however, the chain came off on a bicycle with speeds, then such a danger, as on the old road workers with brake bushings, comments. You have hand brakes that are NOT connected in any way with the chain drive. But there is another danger. Without the presence of a hitch with the rear wheel due to the slipping off the chain, the drive front sprocket with connecting rods begins to rotate freely with the carriage. This freedom makes movement very difficult. An inexperienced cyclist may lose balance or a foot may fall off the pedal. Returning to the fact that the chain most often flies under heavy traffic and high speeds, such a loss of the pedal will lead to serious injury. In this case, it is much easier to solve the situation if you have contact pedals or good spike pedals installed.

Another unpleasant case is extreme skiing. If you are going through a difficult section or landing after a long flight, a loose chain can cause a very serious fall. Here, the legs can also jump off, since there will be no predictable load on the pedal, and the carriage can turn over several times from surprise. All this is dangerous.

Well, two cases that are dangerous for all types of riding are the physical loss of the chain somewhere on the track or the falling off the chain into the spokes or other moving parts of the bike. In the first case, you will need to go to look for a chain, because It will NOT work without it, but in the second one you can make a juicy cross-wheel.

The chain came off. What to do about it?

The drive chain is one of the most important components of a modern bicycle. The chain drive has been used on all types of bicycles for a long time and has proven itself from the very best side. There were bicycles with belt pretexts and even with a cardan shaft, but the chain was the most widespread.

A bicycle chain has a number of advantages and disadvantages. And although there are much fewer disadvantages than advantages, there is one very significant drawback. Often from a cyclist, who is digging with a bicycle turned upside down in the middle of the road, you can hear. yokarny babay, the chain has come off. This is a real attack that sooner or later any bike user faces and must be fought.

How to fix a loose chain

In all cases, an individual approach is required. Most often, you need:

  • Assess chain wear and replace chain and transmission if high wear occurs. Please note that it is better to change the entire set at once. system or stars, chain and cassette.
  • Cleans the entire system of dirt / debris and grease the chain. Eliminate link jam.
  • Tighten the chain to the required tension. Shorten the chain by a couple of links.
  • Align the chain-line, make sure the chain is of the correct length and check that the system can interoperate with the short / long foot.
  • Check the switch setting accuracy.
  • Install the chain guide for intensive riding.

The most dangerous combination is a chain jam. The chain falls into the space between the connecting rods / stars and the frame and does NOT come out from there NOT under any pretext. The application of force will only damage the frame. In such cases, you need to very carefully look for the position in which the chain falls into the gap. Such a situation will surely come across. Do not pull the chain with great force. the chain itself will deteriorate and you can cause irreparable damage to the bike frame. There have been cases when a cyclist pulled the chain so hard that he literally sawed his frame. And the slightest damage leads to the formation of a crack.

Note that occasional chain bouncing is common on a bicycle. This is a regular mode of operation, if you will. But these cases must be that very rare. If the chain jumps off twice per trip, then this is already an unacceptable boundary. In addition, a standard bike should ride over spines, rocks, and slide down slides on primers while keeping the chain in place. High to Medium Shaking / Movement is the standard setting. If there are constant deviations, then it’s time to start repairing.