Getting Rid of Chain-Suck : ALL Methods

Copyright Jonathan Levy, 2000. All rights reserved.

The two basic aims for alleviating chain-suck, are :
a) Tooth pressure-faces suitably shaped to disengage, even if loaded
b) Disengaging bottom teeth subjected to little or no chain load

  1. Check for the obvious issues such as accident damage to chain-rings (bent), to teeth (bent) and to chains (twisted or tight links), and visible or reported mechanical inadequacies of particular drive-trains arising from poor design, materials, or manufacture. Repair affected components (if feasible), or replace them. Sometimes chain links become tight because of poor maintenance and riding through a lot of mud ; this can cause chain-suck ; the simple solution is to clean the chain thoroughly ; then strongly flex the stiff sections of chain (or stiff individual links) sideways/horizontally, to loosen the links ; and finally lubricate the chain well.

  2. If necessary, use the Chain-Suck TEST to isolate the cause of the problem ; then implement the fix.

  3. The most common solution to chain-suck is to install a new chain-ring :

    • Replace the worn chain-ring (usually the granny) with an accurately machined component of strong hard material which is also tough. Avoid all aluminium; use only suitably specified steels (eg appropriate type of stainless steel), or use titanium. If it is a larger chain-ring (say 30 or more teeth), only then is a good aluminium alloy acceptable.

    • If the existing granny-ring is symmetrical, flipping it over to use its unworn trailing tooth faces, can also provide a good solution.

  4. Rotate the fastening position of the chain-ring by one or more bolt-holes. This is a temporary solution which does not always work, but can be carried out on-the-trail, using only a single allen key wrench. It moves those teeth which are usually more highly indented or hooked, away from the critical high-load zones of the crank's cycle. If the chain-ring has special attachments or individually shaped teeth to ease gear changes, then such rotation can lead to less crisp gear changes. It might resolve 1-ring suck temporarily, but it can worsen (or alleviate) 2-ring suck.

  5. Filing Tooth Profiles (see separate document) is a method for the technically proficient to reshape worn pressure faces of the teeth (tooth side-burrs are not the issue) to establish a better tooth profile. This method can also be used on-the-trail. If a new chain is to be installed, this method should not be used as a long-term solution.

  6. For 2-ring suck, resolving granny-ring problems might also resolve this problem. However, alternative or additional steps might be needed to resolve any mismatch in tooth/chain pitch which may exist across adjacent chain-rings ; their rotational alignment to each other may be unsuitable. One or more of the following eight options may be needed :

    The next four options can be used individually or in combination to adjust the rotational alignment of teeth on adjacent rings ; this will improve matters if the change is in the right direction, but will worsen matters if it is not.

    • Install a different granny ring and/or middle ring with different tooth shape, and/or also a different manufactured alignment of teeth along its circumference

    • Install a ring with a different number of teeth, to change the tooth-ratio of adjacent rings, and hence the relative alignment of teeth

    • Rotate the fastening position of the chain-ring by one or more bolt-holes, which will change the relative alignment of teeth.

    • Adjust the adjacent granny/middle rings so that the small amount of play which exists in their bolt-holes is used to fasten the rings at that extreme of play which reduces problems

    For a set of new chain-rings, for which the problem just cannot be resolved by any of the above measures :

    • It may be necessary ultimately to get a different make/design for the complete set ; this may also involve a different set of cranks ; it is advisable to get a well matched set, with tooth ratios and tooth shaping/ramping generally known not to suffer this problem, and from a single manufacturer.

  7. For detail on anti chain-suck plates , click the link

  8. If you have installed a new granny-ring or flipped the ring to use its unworn faces, then replace the chain preferably; definitely if its stretch is greater than 0.3%.

  9. If any rear sprockets are worn and the new chain "skips" over teeth, also replace those sprockets.

  10. Clean and lubricate the drive-train frequently to reduce chain and tooth wear.