akmal's bike park

akmal's bike park

Friday, 2 July 2010

Chainsuck Sucks

This diagram by Jonathan Levy summarises chainsuck. Read the whole article to understand fully.


No, it's not a tounge-twister.
I suffered chainsuck during KLMBH Epic Bash 2010, and to some extent it partially ruined my ride.


Here's my quest for answers:

What actually is chainsuck; what causes it?

What's the effect on the drivetrain (and my pocket?)

How to cure it, and how to avoid it?


Google 'chainsuck', and the top hit is the link to Jonathan Levy's article:

Apparently, his article is being referred to (and some are republished therein) in other links.


The in-depth explanation about chainsuck by Mr. Levy would be a comprehensive read for us to understand all we need to know about chainsuck. It is rather long and refers to a lot of links (necessary to explain relevant terms and mechanisms), but go slow with it and you'll get through at the end of it with "Owhh... so that's why...".


Go here for a much shorter article (with photos!).


Mind you, Mr. Levy's article covers all aspects pertaining to chainsuck. So, have a go about it before you suffer any chainsuck at all.


So, what do I understand about chainsuck?

Well, it's not caused by chain wear, rather by the chainring wear. Inche Panjang was correct, in our short discussion yesterday evening. In my case it's the granny ring, which, as pointed out by Levy, is the usual suspect.

You may experience chainsuck even if the chain is new.

The chainsuck occurs with the presence of mud and grit which adds friction to the chainring – chain interface. Well, there were copious mud and grit during the bash last Sunday, effectively stripping off the lube on my chain.


The mechanism of chainsuck, in the words of Mr. Levy:

When Tooth-Wear, and Low-Stretch (New) Chains, and High Friction (eg Mud) are present in various combinations, they cause the chain-ring's bottom teeth to be loaded or overloaded, and also resist disengagement of the chain. The chain does not have enough weight to disengage itself from the bottom teeth of the chain-ring in these circumstances, nor can the rear-derailleur spring provide enough tension after the chain starts being dragged up. The links are carried around and up the rear of the chain-ring under continuing load ...the chain sucks !!


The cure?

A cheap remedy would be to file the tooth profile of the ring so that the 'hook' is removed thus making the chain disengaged from the ring when it goes past the bottom point.

Or, the granny ring can be reversed as it is usually symmetrical  and flat (without ramps and pins for shifting).

The better remedy (of course) is to get a replacement ring, and it is recommended to change your chain when you do so.


Okay, then, so that's the bit where my pocket (and drivetrain) will be affected.
Thanks for reading.
Hope you gain as much as I do (or better).
Have a great weekend, without any chainsuck.
Meanwhile, have a go at my daughter's favourite tongue-twister:
how much wood would a woodchuck chuck, if a woodchuck could chuck wood?

No comments: