Broken the chain twice in one ride.

[Tom B]

Went out on the 2 month, 200 mile old MTB, having done pretty much all the 2500ft of climbing I was looking forwards to enjoying some DH. After the first couple of hundred yards of sloppy muddy tracks I hit some bumpy rocky stuff and then the chain snapped. It felt that perhaps the chain had dropped off the chainring prior.

To my suprise when i took the chain off it seemed in pretty good order, it seemed clean and nowhere near as dirty as I was expecting given the conditions. It wasnt oily, but felt greasy. I guess the oil I applied pre ride had washed off in the vast amount of water I'd been through. - Perhaps I'll use the snot like Extreme wet Lube next time.

I freewheeled/pushed the bike down the hill to the LBS who kindly supplied and fitted a new quick-link. Then about 3miles later again when I was descending some rocky stuff the same sort of thing happened again. It seems like that the side plates have been stripped off the chain on a couple of links.
There is a little bit of pant chipping on the chainstay behind the chainring perhaps suggesting the chain has been up there and then the ring has stripped the chainplates. Seems like a crap design not to allow more clearance if that's what happens if it drops the chain.

The bike is due its 6week service so I'm going to let them see what they make of it.


What do you guys make of it?

Im normally a 8spd sort of guy, so are any 10spd chains better than others?

 

[Racing roadkill]

I'd guess that your front mech isn't adjusted / indexed properly, and the chain has been rubbing against it, and not dropping cleanly on a down shift. It's possible that the quicklinks haven't been locked in properly as well. As for chains, I find Clarkes ten speed, or KMC 10 speeds to be most durable.

 

[Globalti]

It looks like a badly-made chain to me; what brand is it? I've got an almost unused KMC 10 speed chain with the spare links and a joining link that you can have for beer money if you fancy picking it up from north Blackburn.

 

[raleighnut]

10 speed chain will only work on 10speed transmission.

 

[Racing roadkill]

10 speed chain will only work on 10speed transmission.

Not quite, it'll work on a 9 speed quite happily, possibly an 8 speed, and maybe an 11 speed, if your careful.

 

[raleighnut]

Not quite, it'll work on a 9 speed quite happily, possibly an 8 speed, and maybe an 11 speed, if your careful.

I thought they were narrower across the roller than a 3/32 (5-8 speed) chain.

 

[Racing roadkill]

I thought they were narrower across the roller than a 3/32 (5-8 speed) chain.

The rivet width is the main difference ( the number of links may be lesser on a fatter chain as well).There is a fair bit of overlap, between the chains. They aren't designed with a tight enough tolerance to be just for one speed. It's trial and error if you go more than a couple of speeds lower, You have to be more careful if you use a fatter chain, with a higher speed set up, ( fatter chains don't fit between thinner spaced sprockets and chain rings, quite so readily).

 

[raleighnut]

The rivet width is the main difference ( the number of links may be lesser on a fatter chain as well).There is a fair bit of overlap, between the chains. They aren't designed with a tight enough tolerance to be just for one speed. It's trial and error if you go more than a couple of speeds lower, You have to be more careful if you use a fatter chain, with a higher speed set up, ( fatter chains don't fit between thinner spaced sprockets and chain rings, quite so readily).

I understand that a 10 speed chain is needed on a 10 speed rear cassette (that's why I fitted one to my Campagnolo Centaur/Record equipped bike) but didn't realise that I could fit £40 chains on my others instead of the £12 ones I've been using.

 

[Pale Rider]

I thought they were narrower across the roller than a 3/32 (5-8 speed) chain.

In old money, a 10-speed is 11/128, so that's 1/128 narrower than a 3/32 which would, of course, be 12/128 if expressed that way.

Not a lot, and probably all but interchangeable.

But there's no point in going outside factory spec when there's no need.

If it was me, I would replace the broken chain with a not quite bottom end 10-speed, such as this one:

http://www.wiggle.co.uk/kmc-x10-93-10-speed-chain/

 

[Racing roadkill]

I understand that a 10 speed chain is needed on a 10 speed rear cassette (that's why I fitted one to my Campagnolo Centaur/Record equipped bike) but didn't realise that I could fit £40 chains on my others instead of the £12 ones I've been using.

But a 40 quid chain is better than walking home, if that's all you've got with you on a ride, because you've got the wrong bike / spare chain combination. You can always sort it out when your back home.

 

[Yellow Saddle]

Went out on the 2 month, 200 mile old MTB, having done pretty much all the 2500ft of climbing I was looking forwards to enjoying some DH. After the first couple of hundred yards of sloppy muddy tracks I hit some bumpy rocky stuff and then the chain snapped. It felt that perhaps the chain had dropped off the chainring prior.

To my suprise when i took the chain off it seemed in pretty good order, it seemed clean and nowhere near as dirty as I was expecting given the conditions. It wasnt oily, but felt greasy. I guess the oil I applied pre ride had washed off in the vast amount of water I'd been through. - Perhaps I'll use the snot like Extreme wet Lube next time.

I freewheeled/pushed the bike down the hill to the LBS who kindly supplied and fitted a new quick-link. Then about 3miles later again when I was descending some rocky stuff the same sort of thing happened again. It seems like that the side plates have been stripped off the chain on a couple of links.
There is a little bit of pant chipping on the chainstay behind the chainring perhaps suggesting the chain has been up there and then the ring has stripped the chainplates. Seems like a crap design not to allow more clearance if that's what happens if it drops the chain.

The bike is due its 6week service so I'm going to let them see what they make of it.


What do you guys make of it?

Im normally a 8spd sort of guy, so are any 10spd chains better than others?

You've given us some clues as to what happened.

Firstly, the chain on there is a good quality KMC chain. What happened is not the chain's fault but a combination of two things - dirt and worn chainring.

The deep scratches in the chainstay were caused by chainsuck. Your small chainring is worn to a point where, when the chain is dirty as you describe, it doesn't release at the bottom as the chain enters the return run. Instead of releasing, the chain moves back up the chainring, taking up slack from the spring in the derailer and eventually jamming under itself. This could have happened partially or fully. A full chainsuck causes a sudden stop in crank rotation and often it rips the derailer off the frame and into the spokes. A partial chainsuck is when the chain rides up the back of the chainring but releases before it jams itself. It sounds as if you had partial chainsuck. I guess this from your guess that the chain dropped down just prior to the incident. That drop-down was probably chainsuck and damaged the chain.

Chainsuck happens when you are pedalling hard, in very dirty conditions, with a worn chainring. I can see your small chainring is worn by the forward-facing hooks. Such hooked teeth on a small chainring doesn't release the chain well, especially if there is mud in the mix. It doesn't happen on big chainrings.

The chain broke by forcing the sideplates open and ripping the rivets through the sideplate. The first incident damaged two plates and only one was spotted and repaired the first time. The second plate failed during a gearchange.

This doesn't mean the entire chain has to be discarded. If you have enough links, inspect it properly, replace the bits that need replacement and ride on. But, replace that chainring.

 

[Pale Rider]

Is it likely the inner ring has worn to the point of chainsuck in 200 miles?

The OP presumably doesn't use that ring all the time, so it will have done even fewer miles.

 

[Jody]

Is it likely the inner ring has worn to the point of chainsuck in 200 miles?

The OP presumably doesn't use that ring all the time, so it will have done even fewer miles.

I think the picture is deceptive with regards to wear. Its hardly taken the pain off the ring never mind being worn badly enough to be replaced.

Its definitely had some chain suck looking at the amount of paint chipped off the frame

 

[Yellow Saddle]

Is it likely the inner ring has worn to the point of chainsuck in 200 miles?

The OP presumably doesn't use that ring all the time, so it will have done even fewer miles.

You are probably right. I didn't pay attention to the 200 mile bit, but just looked at the bit of inner ring I could see and it looked hooked forward to me.

Nevertheless, chainsuck has three contributing factors and a combination of any two can cause it.

1) Chainring size - smaller is worse
2) Smooth sticky mud or very gritty mud
3) Chainring wear.

 

[RRCC]

Possible causes of chain suck other than wear>

• Chain too slack:

1. Too long - it should only be one link longer than the minimum needed to go round the big/big combination
2. gear range is more than the amount the rear changer can handle
3. rear changer gummed up and unable to take up slack

• Damage to little ring wear/burs/bent teeth preventing the chain releasing
• Damage to the next ring
  
• Poor gear adjustment
  
• Mud

Prevention

• Avoid the smaller sprockets when on the little ring
• anti chain suck plates

Needs sorting as it can write off a frame due to damage to the chainstay and/or leave you stranded or removing the chainset to free the chain.