Broken Chain

[DV1976]

I managed to break my chain twice in two days... Both times happened while I was climbing up a hill and the chain was on the small chairing (I have a Shimano 105 triple chainring) and the 3rd largest sprocket. Both time it felt like the chain slipped first then it was caught somewhere and broke. Both time it happened when I applied force to the pedals trying to accelerate (I'm not the epitome of smoothness) I had it fixed the first time, the mechanic said that he couldn't figure out why it had happened and the gears worked OK. I made the mistake of not checking the chain myself, took the bike for a ride and broke it again. When I checked it afterwards 5 of the links were cracked so it was just a matter of time... I can't figure out why it happened though... The gears change OK (both front and rear), I clean and lube the chain on a regular basis, and the chain (and cogs) hadn't done more than 1000 miles. As I said it felt like slipping and it's something that it happens when I'm using the small chainring. I have noticed a small chattering from the front derailer that I haven't been able to deal out but I don't think it's causing the problem... I'm at a loss...
Any ideas?

 

[Eastway82]

If you regularly ride with a heavily crossed chain (especially big ring/big rear sprocket), you might be stressing the chain, which could lead to cracking. It's also possible it was just a **** chain...
Once it had broken once, the bike shop should really have checked the rest of the chain and replaced it if there was the slightest doubt - it's not like a new chain's going to break the bank...
The noise from the front derailleur probably isn't related to the chain problem. It's probably just adjustment, but it's harder to finesse that with the shifters if you have a shimano setup - on Campag you can always tweak the front shifter a little to get rid of noise.

 

[Albert 50]

(I have a Shimano 105 triple chainring) 9 or 10 speed chain?

 

[DV1976]

Eastway82: I try my best not to cross the chain too much. For example I never go lower than the 3rd sprocket (counting from the biggest) when I'm on the small chainring and I never go higher than the 5th when I'm on the big chainring. I use the middle sprockets with the middle chainring. I also take care not to stress the chain when shifting. That is why I can't understand why the chain failed... I agree though that is hard to adjust the Shimano front derailer. It has two positions for the small and middle chainrings (supposedly to avoid "chattering") and once is detuned is impossible to adjust.



Albert 50 9-spd chain

 

[F.G.]

I had my chain break about a couple of months ago, thankfully it had just sprung apart at the connecting link, so I could JUst pick up the bits and put it back together (although the rest of my deliveries that day had black fingerprints all over them). What the problem was, was that the chain had caught between my two chainrings ( I've got a road bike chainset on my mtb), it had locked and the consequently broken.

In my case this was because of a badly adjusted deraileur, which it souns like yours might be (with the 'chattering'). But I did find on a previous bike of mine that this can also happen if you back pedal and you have a bad chainline. that's to say if you have it on the highest front chainring and the lowest on your cassette, if so the disparity between them can pull the chain across. (if its this second problem there's not much you can do except either avoid that gear combo or perhaps get a shorter bottom bracket (if your chainset will still fit)).

I don't know if any of this is usefull to you, so good luck and I hope you find out what the problem is!
yrs, F.G.

 

[DiabloScott]

I think most chains break because they were damaged on installation and/or removal- you push the pin out, push the pin in - pretty difficult to get it aligned perfectly... the hole gets deformed, the plate gets cracked or bent... that's what happens - especially if you take it off frequently. Using a quick link will help, or just not taking your chain off.

 

[DV1976]

I think most chains break because they were damaged on installation and/or removal- you push the pin out, push the pin in - pretty difficult to get it aligned perfectly... the hole gets deformed, the plate gets cracked or bent... that's what happens - especially if you take it off frequently. Using a quick link will help, or just not taking your chain off.

Thanx for the answers guys...
Diabloscott the first time the chain was taken apart was for the repair... Bad/careless installation might had caused it but when I checked it out I found that 5 links were cracked around the pin holes and none was the one that was fixed...

 

[Eastway82]

But I did find on a previous bike of mine that this can also happen if you back pedal and you have a bad chainline. that's to say if you have it on the highest front chainring and the lowest on your cassette,

yrs, F.G.

It's just not a great idea to be putting that much sideways strain on your chain at the same time as stretching the rear derailleur as far as it'll go. You could get the same gear using the next chainring down and a few sprockets up, so why go for the extra friction/mechanical stress option?

 

[hd reynolds]

I managed to break my chain twice in two days... Both times happened while I was climbing up a hill and the chain was on the small chairing (I have a Shimano 105 triple chainring) and the 3rd largest sprocket. Both time it felt like the chain slipped first then it was caught somewhere and broke. Both time it happened when I applied force to the pedals trying to accelerate (I'm not the epitome of smoothness) I had it fixed the first time, the mechanic said that he couldn't figure out why it had happened and the gears worked OK. I made the mistake of not checking the chain myself, took the bike for a ride and broke it again. When I checked it afterwards 5 of the links were cracked so it was just a matter of time... I can't figure out why it happened though... The gears change OK (both front and rear), I clean and lube the chain on a regular basis, and the chain (and cogs) hadn't done more than 1000 miles. As I said it felt like slipping and it's something that it happens when I'm using the small chainring. I have noticed a small chattering from the front derailer that I haven't been able to deal out but I don't think it's causing the problem... I'm at a loss...
Any ideas?

Chain breakdown usually occur during chainring jumps when the links are almost diagonal to the rings. This is the time when they are most vulnerable because the forces acting on the links try to pry them open when they are diagonal. The weakest link (no pun) is the connecting link specially if not properly seated. 10s chain nowadays like campy's and shimanos have a specific link that can only be used once. Unless this link is properly seated and centered the chain is already compromised. However there is a solution from a variety of sources like Wipperman Conex, KMC and even Mavic. They have slotted links that lock in place and are pretty reliable.

 

[F.G.]

My gear setup on my current mtb and my previous one is 42/52t on the front and 28-11t 7speed cassette on the back. This means that (I havn't actually worked this out mathematically) the gear combo's don't overlap like on a normal mtb. I have heard that you shouldn't stretch the chain with high/low front/back combo's, but working as a courier in cities such considerations go out of the window! F.G.

 

[DV1976]

thank you all for your contributions