What is the chain suck and what causes it?

chain suck

The chain suck and what causes are systems of bicycle-

There is a lot to be said about chain suck, whose literal translation sucks of the chain. It is a phenomenon that usually occurs during the gear shift, more frequent best bike us in the middle or lower gear changes when you are pedaling harder.

The result is that you have to stop abruptly and get off the bike to unscrew the chain that attaches to the frame and the crown; this may damage the frame and/or the transmission.

Possible Causes

The chain suck is usually caused by a combination of too much mud and wear. However, even in a new transmission system, it can also occur. A crank with the intermediate or small worn crown is a good example: added to the excess of mud, the situation can get worse. But, incredible as it may seem, there is the possibility of chain suck when the chain is very dry, that is, lack of lubrication, even with the system in good condition.

The chain suck can also occur when there is a misalignment of the crank in relation to the frame (chain line) and the chain line; if the system is new, this can become critical because there are sharp corners in the new parts, which only improve with use.

For a stent crown, the best solution is obviously to replace it. With this, you may also need to replace the chain and the cassette if the chain suck is over tightening. Best brands and models of road bikes is the best cycling-

The following procedure can keep things running for a long time if the money is short, the stores are closed or you want to wait until the summer to replace. They are tips to minimize or avoid the occurrence of chain suck.


  • Clean transmission system and remove crankcase. Often a crank puller is needed.
  • Check the middle and lower crowns, which are the main point of occurrence of the chain suck. Note that hooks will appear over time in the worn crowns, since the crown material simply does not go away with the use: part of it is attached to the crown as if it were kneaded in your tooth, leaving a burr that makes it wider and this, hook shape in the tooth, causes difficulty for the chain to come off at the bottom of the crown due to the low load on the bottom of the chain.
  • “Being outside the chain line”, that is, the misalignment of the crowns in relation to the frame also influences the phenomenon. This is much more complex than the worn case, so it’s best to look for a good mechanic.


Attempts to improve

With a round file and the side burr accumulated on the crown tooth with a gentle movement; remove this accumulated material best bike us and then assemble. Test everything clean and lubricated.

Bikes chain suck must be covered in the mudguard. So, It is important to have our knowledge about this-

Alignment of crowns

Most cranks require a chain length of 47.5 mm or 50 mm. This measure counts from the top of the middle crown to the virtual center of the frame. For double crown on road bikes chain suck, the measurement is 43.5 mm.

Usually, the manufacturer informs the chain line for each crank.

Chain line and its standards:




Double Road

43.5 mm

Measured to the midpoint between crowns. With a typical crown spacing of 5 mm, which places the interior at 41 mm, the exterior at 46 mm.

Triple Road

45 mm

Measured up to the middle crown.

MTB Triple

47.5 – 50 mm

Measured up to middle crown. Usually, 47.5 mm is used, but frames with large saddle tubes may ask for 50 mm because of the larger diameter tube positions the shift mechanism more to the right.

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