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I have a Lappierre Zesty 314 (2012). I'm running xt rear mech, a slx front mech, and my crank is xt and rear cassette is xt and xt chain. I went to the forest of dean and after the day was over I snapped my chain! So I picked up a sram chain for my bike and now when I pedal hard it slips with a big bang. I have new eastern havens so my hub is fine. Can you help with any ideas to help me solve this? Shall I get a new rear cassette?

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My guess is that the new chain is the wrong size, or you did not properly adjust its length when installing. – Daniel R Hicks May 28 '14 at 19:12
Also, if your chain "snapped" that suggests that something in the drive train may be bent or damaged. – Daniel R Hicks May 28 '14 at 19:17
(According to what little I find on the bike the chain is a "10 speed".) – Daniel R Hicks May 28 '14 at 19:18
Check things out before you go spending money. As well as other suggestions, is your rear derailleur ok? What happens when you put it on a stand? Does it only jump under load? Any idea what the bang is? Or where its coming from? – PeteH May 28 '14 at 19:45
+1 check something in your drive chain. I got a notch in my front derailleur which chews and snaps chain - so check front and back drive-train. OFTEN rear derailleur can get a bit twisted or bent. Check does your rear derailleur cog line up correctly with your rear cogs? Applying some gentle brute force to rear derailleur can help. This is very good: – gaoithe May 14 '15 at 16:40

Look up the proper chain for the components. XT is not a size - that is the group level. You should size the chain for the number of speeds (gears).

Inspect the cassette. As they wear the teeth get sharper spaces get longer. Visually compare it to a new cassette even if you are looking at a picture.

If your chain snapped then possible something else is damaged. Inspect all the drive components.

A cassette typically last 2-3 chains. If you get a new cassette then change the chain.

A worn chain wears a cassette down faster.
And a worn cassette wears a chain down faster.

A chain is cheaper and easier to change so cheaper to stay with a fresh chain.
There are tools to measure chain stretch.
Replace a stretched chain.

A new chain on a worn cassette will jump - basically both the chain and cassette stretch.

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+1 for pointing out that a cassette should last longer than a chain. Despite other answers there's not normally a 1:1 relationship between the two. – PeteH May 28 '14 at 19:42
Do you suggest to change cassette and chain together? – JigarGandhi Oct 21 '15 at 6:21

Typically you'll want to change your chain and cassette together, since they will both be worn, so it's not surprising that you're experiencing some slipping. It's also possible that your existing cassette is bent or damaged in some way rather than just being worn. I had an old XT 9-speed cassette where I somehow bent a few teeth to the right in the middle range, and even though it was barely noticeable, it made those middle cogs totally useless under load.

I assume you also bought a new chain that's the appropriate width for your rear cassette (9, 10, 11-speed, whatever). So if it's adjusted well and you have the right chain, I think it's safe to say that you'd benefit from also replacing the cassette.

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Both be worn but not at the same rate. Cassette's usually last a couple of chains depending on length between changes. – AliGibbs May 28 '14 at 20:30
Rear cassette maybe last through 5 chains. Front rings maybe 10 chains. Some front rings might have alot less use than others.… – gaoithe May 14 '15 at 16:50

Chain slip, after replacing a chain, usually indicates worn cog(s) and/or chain-wheel. This can be avoided by replacing the chain early, before major wear has taken place. The snapped chain is problematic. The break could have been caused by an extremely worn chain. If the original chain had no master-link, it could be that the pin was not installed exactly as it should have been. This pin could have popped out on a well worn chain. If you still have the broken chain, re-install the chain, replacing the broken link with a quick-link (master-link). Now, does the old chain slip? (be careful during testing) If the old chain does not slip & the new chain slips, then you will need to replace the cassette in order to use the new chain. (one or more chain-wheels may need to be replaced also)

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I'm afraid I think the other answers on here don't have it right. It's unlikely to be your rear cassette which is the problem. Your problem is most likely to be with your chain and rear derailleur. Happily not expensive just can be a bit tricky to fix.

Three things to check:

  1. New chain is the right length? The new chain should have the same number of links as the old chain. Did you line up old and new chain (allowing for wear so the line-up will be asymmetrical!) and put on new chain with the same number of links? I used this recently:

  2. OFTEN rear derailleur can get a bit twisted or bent. You were riding in the forest and chain snapped. Might you have bumped something? :-) Especially your rear derailleur is exposed to bashing off things when mountain-biking. Check does your rear derailleur cog line up correctly with your rear cogs? Applying some gentle brute force in the right place on the rear derailleur can help. This is very good:

  3. Check something in your drive chain. I got a notch in my front derailleur which chews and snaps chain! So check front and back drive-train. Is your back wheel aligned correctly also?

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I think its pretty hard to not align your back wheel correctly these days with vertical dropouts. – Batman May 14 '15 at 17:29
It's unlikely perhaps, . . but probably an obvious first thing to check, especially for those of us who tend to use ancient technology. – gaoithe May 15 '15 at 8:53

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