Why the chain comes off on a bicycle when shifting gears

The bicycle is a unique means of transportation available to everyone. Many people choose it because it has a positive effect on human health and does not pollute the environment. But, while riding, every cyclist at least once, but faced with the fact that the bike chain comes off at the most inopportune moment. Why the bike chain comes off and how to fix the problem, you can learn from this article.

Causes

Bicycle chain can come off due to the following failures:

Warped links.
Insufficient tension (on bicycles without gears and with adjustable transmission).
Damaged teeth in the front or rear sprocket.
Stretching from prolonged use.
Need to have the front derailleur or rear derailleur adjusted correctly.

So check these items to see if there is a solution to your problem.

Buckling of the links

Transmission unit functionality can be impaired if the chainrings are deformed as a result of heavy use and dropping your bicycle. If the chainrings are in poor condition, they frequently fall off from time to time.

To fix the malfunction and to set the course, it is necessary with the help of a squeezer to restore the links. It is better to buy this device in advance in a bicycle parts store and keep it with you at all times. Thanks to its small size, it will not give you any trouble in storage and will help in an emergency situation. If a significant deformation affects a large part of the bike chain, it is easier to replace it with a spare, and straighten the affected cogs.

Weak tension.

As a result of vibration and load, the rear fork may change its position relative to the rear hub axle. This increases the slack in the chainring. A slight jolt is enough to cause the chain to come off. The problem can be easily solved by following a step-by-step procedure:

Place the bike upside down.
Slightly loosen the tensioning bolts.
Move the wheel to the required distance.
Tighten the bolts to their new position.
Check the quality of the tensioning.

You should always have a set of wrenches with you to make quick repairs.

Tooth deformation in the front or rear sprocket

Tooth deformation is usually associated with a distortion of the rear wheel, otherwise known asa “figure of eight“. “A figure of eight” is a bicycle rider’s problem, in which the wheel is distorted and the bicycle cannot perform its intended function.

The problem is solved as follows:

The wheel is removed.
The location of the damage is determined.
The central spoke of the “figure of eight” is isolated.
All spokes are tightened one by one.

Stretched chain.

The derailleur spring has failed to retain the tension and the chain is loose. This defect cannot be repaired, you just have to replace the chain with a new one. This is a rare occurrence. It is almost impossible to repair such a chain.

Incorrect switch setting

This problem is only found on bikes with gears and can be easily fixed by fine tuning the rear derailleur. If you notice that the chain jumps into a different gear when you pedal with maximum force when you do not press the shifting lever, adjust the maximum amount of travel on the derailleur with the two bolts on the derailleur housing.

What to do if the chain on your bicycle comes off

On a fast bicycle, if the chain does not come off between the system and frame, use your hands to slip it onto the chainring and pedal. This is enough to continue riding.
On a single-speed bike, where the chain is tensioned by moving the rear wheel in the fork, the situation is more complicated. You have to turn the bike over and crank the carriage with the system. Try to engage it with the cog of the front sprocket. As you engage, gently guide it back into place with your hands, while still rotating the connecting rods. You can help yourself with this with a regular screwdriver or a stick.
The hardest part is dealing with a chain that has fallen between the frame and the system. Keeping calm, try to find the position it is in in that space.

The situation is made a lot easier if you have a crank pin or a crank puller. If you don’t have one, just push it back in. Rotate it in different planes to find the right angle. If necessary, you can help the chain get out by hooking the sprocket and turning it through the frame. It is recommended to do this only in the most extreme cases. Otherwise there will be a defect on the aluminum frame and it may be damaged.

On a fast bike

Why does the chain come off on a speed bike? The transmission unit includes a chain that consists of cassettes with multiple sprockets. To determine and fix the source of the problem, you need to know:

If the chain on a speed bicycle is constantly coming off, be sure to pay attention to the condition of the stars. If a defect is detected, change it to another sprocket to get to a point where a better repair can be made. Do not use the derailleur until then. The defect is corrected by replacing the deformed sprocket with a new one. If the assembly is not disassembled and the entire cassette is noted to be defective, it will also have to be replaced.
The chain on a bicycle with speeds may come off due to a speed setting failure. Check the tuning to rule this out as a possible cause. Do the check by following a specific pattern. After the main fault has been corrected, place it back in its original location.
Disconnect the links with a squeegee before putting it on the bike. If the chain is new, start by measuring off the correct length by slipping it over the large cassette block sprockets and connecting it. Remove the excess links using the above tool. Turning the screw will dislodge the unwanted link axle and some of the chain can be removed. It is then passed between the derailleurs and connected with the same tool.

On a children’s bicycle.

If the chain slips on a children’s bicycle, the same work is done as on an adult bicycle, taking into account the design of the bicycle itself.

Conclusion

The basic rule of repair is patience and endurance. When you decide that the situation can no longer be changed, but continue to stubbornly look for a way out, the chain will jump out of even the most hopeless position. Do the work without sudden movements and the use of excessive force. This is the only way to fix the problem and avoid damaging important parts of the bike.