Chain Suck?

[Samcat]

I'm in need of a bit of advice, I bought a new mountain bike from my LBS and it was set-up by them. I have now started to experience what they have called 'Chain suck' whereby the chain loops up and gets stuck between the front chainwheel and the frame, usually when changing down to a smaller front cog.
I doesn't happen all the time and is impossible to reproduce with the bike on a stand. The bike has been returned to the shop for them to investigate and they checked all the gear adjustments etc. but it has happend twice since. Is there any known fix for this problem or could it be down to my lack of technique on the gear change?

[itsnotarace]

When you are changing gear on the front 3 rings, just ease off the pedalling a fraction and give it a chance to change before re-applying the power via the cranks. If you change gear at the front under power it puts a lot of strain on the chainrings and the mech and the chain can do unpredictable things at best, at worst you will break something.

You can also get a chain catcher but this should not be necessary if the limit screw on the front mech is adjusted correctly and you ease off the power.

Forward observation and proper planning of upcoming obstacles will become easier with time so you don't get caught out in the wrong gear

[P-Jay]

That's annoying, sorry don't mean any offence, but is your chain properly lubed?

Only time I suffer from chainsuck is if it starts to run a bit dry.

[Jameshs]

I agree with P-Jay here, check the chain has a decent lube on it and nothing that too sticky

[Samcat]

Thanks for some comments, yes I agree about the planning your gearing better comment, I'm still getting used to the bike and I'm not that familiar with some of the trails so I have been known to get 'caught-out'
I have been lubing the chain with some oil from the bike shop, the advice I was given was to; oil it up, then wipe off the excess, how often should you re-lube, the chain seems pretty oily to me.

[P-Jay]

Samcat said:

I have been lubing the chain with some oil from the bike shop, the advice I was given was to; oil it up, then wipe off the excess, how often should you re-lube, the chain seems pretty oily to me.

Yeah sounds about right, the only other thing I can think of is worn chainrings, but if it's new that wont be a factor.

I used to lube every ride, but now I use Chain-L No5 which is meant to last months, but I still end up re-doing it every 3rd ride or so.

[HundredthIdiot]

Chain keeper?

[JPJ]

They've probably checked, but no harm in also checking for any bent/stiff links in the chain or more likely any damaged teeth on the chainrings.

[HundredthIdiot]

JPJ said:

They've probably checked, but no harm in also checking for any bent/stiff links in the chain or more likely any damaged teeth on the chainrings.

Yes, I was plagued with chain drops on my road bike until I turned my bike upside down and noticed that the chain was slightly derailling off the bottom at a bent tooth hiding behind the crank.

[ccr32]

As has been said, check for stiff/broken chain links, bent chainrings, and anything that could be obstructing the ramps and gates on the chainrings (including muck and gammy old bits of dirty oil).

[Parrot of Doom]

This type of problem can only be caused by the chain, or the front chainring.

Its either:

: Lack of lubrication, leading to links which don't rotate as they should, and which therefore force the chain to hold its shape as the links leave the chainring
: Faulty link, same symptoms as above
: Hooked or bent teeth on the chainring


That's pretty much it. I wouldn't mind betting that the LBS hasn't removed the delivery grease from the chain. My advice would be to remove the chain, soak it for a few minutes in white spirit or turps, dry it off, and then soak it in thin oil. Then wipe the drivetrain down with a white-spirit-soaked rag, and reinstall the chain.

Edited by Parrot of Doom on Friday 13th August 16:24

[HundredthIdiot]

What's "delivery grease"? AFAIK chains come pre-lubricated, and should not be cleaned (on a road bike at least) for the first couple of hundred km.

[Parrot of Doom]

Sorry but I don't agree. The "pre-lubricated" in my experience is the same stuff as is applied to car brake discs. Its horrid, gunky sticky stuff that should be removed before the chain is lubricated properly.

[HundredthIdiot]

Parrot of Doom said:

Sorry but I don't agree. The "pre-lubricated" in my experience is the same stuff as is applied to car brake discs. Its horrid, gunky sticky stuff that should be removed before the chain is lubricated properly.

Fair enough, but received wisdom differs. They put that stuff on for a reason.

Then again, different chains use different stuff. According to this, Shimano XTR chains come with nasty sticky stuff. I only use SRAM road chains, and find the lube they come with is fine for a fair few rides until the first proper cleaning.

[Parrot of Doom]

The only reason they put it on is to stop the chain rusting in its box.

I know from bitter experience, a greased chain can be unrideable.

[Mars]

Fuel injector and Carb cleaner, made by Wynns, bought in Halfords. It'll clean off anything back to the bare metal. Whizz the chain round a few times while spraying this at it (you might want to cover the rest of the bike), then leave it to evaporate and re-lube. If that doesn't fix it, you've got something bent.

[dubbs]

2 issues I had after my Ibis build:

1. bedding in and stretch of pretty much everything - the whole bike felt crap after about 90 miles but a proper service fixed it all (I'm mechanically inept so 15 mins with GT40 might have achieved same result) mainly cables and rear brake though (cos I'm a DH poof!)

2. I found lube to be a big issue on the new bike in terms of chain suck, never was on the hard rock (anything was fine) but the Ibis just had everything more honed (tolerances and I think a design issue with rear end) so any issue like dirty chain really noticed. I find king of lubes blue or red really good on bot mtb or road - you'll get loads of recommendations - I prefer a drier teflon based during summer as it seems to work and I'm damn lazy so don't want to clean the chain and surrounds every 5 mins that works well for commutes too

[Samcat]

Thanks again for some good replies.

I think PoD may have a point about the Pre-delivery oil on the chain, the chain was lubricated with a 'waxy' type lub when I first got the bike. I didn't clean this off, I have just added chain lub to the chain.

Since I first posted I have heavily oiled the chain, wiping away the excess, and I've done two rides, Llandegla and Beddgelert Forest with no problems, but I have been taking care not to apply too much power when changing between the front cogs.

So I'm going to conclude that lack of correct lubrication and a bit of a dodgy technique are to blame in this case, you live and learn.

Edited by Samcat on Monday 16th August 10:09