Cycling classroom: basic knowledge about the length of a bicycle chain

Cycling classroom: Basic knowledge about the length of a bicycle chain

Chain length is really important:

The length of the chain is often overlooked when assembling a bicycle or changing a chain. In fact, the chain of bicycle displays that are often seen in the dealerships are too long. The small negligence of the brand's entire vehicle at the factory is easy to get off the chain during the ride or the shift is not smooth. . Too short a chain can lead to catastrophic consequences, because too short a chain can cause the chain to be transferred to the maximum gear of the flywheel and cause the chain to be over-stretched for a long time. Because the entire rotating system pulls the chain too much when riding, it can even tear the transmission and break the chain, not to mention the high maintenance costs caused by this carelessness.

XACD cargo bike

About the choice of post dialing:

The rear derailleur of your bike is important in the length of the chain. It can make the chain have extra slack on the rear dial and the flywheel small tooth number and the disc set, or it can provide the tension compensation in the large disc of the flywheel and the large disc of the sprocket by the action of the rearward spring. . There are long, medium and short legs respectively. The general rule of choice is that the longer you need a large gear ratio, the longer the leg is selected, because it can correspond to more shift combinations, if you choose a short leg back and a large ratio of the crankset (such as three-piece The sprocket wheel) requires a longer chain to compensate for the lack of compatibility between the short leg and the rear. If you choose the wrong leg, the length of the leg will easily lead to the wrong chain length. (Small series: That is to say, if you use a three-piece sprocket wheel with a large number of flywheels like a mountain bike, you can choose long legs. The rest can be selected. According to the experience of Xiaobian, do not use the short legs. Cars with highway flywheels, as well as heavy off-road FR to DH-class cars often use short legs)


If the chain is too long, it will make you difficult to change speed, and it is easy to drop the chain, but if it is too short, you will soon say goodbye to your back. Checking the length of your chain is very important!

  some advices

The maximum distance of the bicycle's crankset at the maximum number of discs and the flywheel at the maximum number of discs is the length of the straight line in the upper half of your chain. This data can be doubled to tell you the approximate chain length. (If it is a full suspension frame, ensure that the suspension stroke is completely uncompressed)

Nowadays, the popularity of 10-speed and double-disc sprocket wheel, many people have abandoned the three-disc sprocket wheel, because the three-piece sprocket wheel can not guarantee the maximum number of teeth of the sprocket wheel and the maximum number of teeth of the flywheel. However, please follow the method of measuring the maximum chain number of the tooth plate and the maximum number of teeth of the flywheel. This is more insurance.

Some veterans use short legs to increase the speed of the shift and the maximum drive provided by the chain tension when going uphill. However, this requires the driver to remember that the gear cannot be adjusted to the maximum number of the flywheel, otherwise it will be said that it will be followed by your call. We do not recommend this choice for ordinary riders.

New cars are usually shipped in stock chains, so the length of the chain is not necessarily right when the new car is bought. Remember to check it clearly.

The leg lengths of Shimano and Sram are a little different. Even if the rear-to-back of the different manufacturers' production is different, it is better to check the loading.

Full suspension bike:

The correct chain length is actually very simple. For the designer of the full suspension frame, the rear axle design is often away from the middle axle in order to provide higher pedaling performance (small series: because the full suspension vehicle rear suspension stroke compression After that, the five-way position and the rear axle position will change). Therefore, full suspension vehicles often require longer chains to compensate.


This is how the full suspension bicycle is fully compressed. If your bicycle is using a pneumatic shock absorber, let go of the air inside. (Be sure to remember how much air pressure your suspension was.) If your The rear suspension of the car has a spring, please remove it.

On the shelf, don't let the car be placed underground or find someone to help you. (Small series: Because this can achieve the maximum stroke, the previous gas shock deflation is because the internal air pressure will make the shock compression a little Protect the shock from the damage caused by the triangular pull of the frame. Adjust the shift to the maximum disc and the maximum gear of the flywheel.

This is the chain is too short. Your rear dial will tell you if the length of the chain is appropriate. As shown in the figure, the rear dial has been pulled all forward and the rear leg has been parallel to the lower tube of the frame. If you are going to ride a bicycle, if you just adjust to this position and you are riding hard, be prepared to say goodbye to your rear chain. At this time, add a few sections to the chain.

This is the rearward angle after adding two chains, and it is just a good angle, leaving more margin to correspond to sudden stress.


Turn the crankset to the minimum and minimum flywheel teeth. The picture on the left is the most standard. The picture on the right shows that the chain is too long and the chain is too loose. Let the rear-pushing spring pull the chain on the guide wheel backwards, so that the pulling force will be insufficient, resulting in a slow chain and a smooth shift.

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