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Chain Slipping - help? - Sorted Thanks


Hector
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Replaced my chain on my MTB and the chain slipped so I bought a new cluster. Problem solved till I stood up and applied a huge amount of pressure on the chain (climbing up a hill at max interval). The chain slipped once or twice. Is it possible the front chain rings are worn. If I look at them they look fine. They have done 3000km on a Merida TFS500. I also now have a slight knock that I can feel through my shoes when pedaling. The knock is not consistant, sometimes I feel it my left foot, then my right foot. It is as if the chain is hooking against something. Checked my BB with the chain off - not BB - it spins well and there is no play. Is it possible the new chain is not sitting well with the front chain rings or are the chain rings stuffed? Any suggestions?

The knock was my pedal bearings that had packed up. The slip was due to worn chain rings - thanks for all the adviceHector2010-03-02 00:39:43
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I have exactly the same problems (both of them) In my case the nocking is as a result of stuffed up pedals and the slipping is a result of a worn middle chainring (it looks fine, but obviously isn't)

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Sounds like  worn front chainrings to me , the fact that you had to replace the cassette after putting on a new chain indicates that the next item would be the front chainrings. 3000 km on one chain would result in messing up the front and rear chainblades and cassette specialy if you are a big powerfull guy.

The knocking noice that you feel would be the chain moveing over the chainblade and would only happen if you apply less power , once you apply more it woud slip over the teeth . 

 

 
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A chain doesn't slip unless your gear settings are out!!!

 

Oh yes? I think you need to revisit how chains engage with sprockets and the effect lenghening has on driving and driven sprockets.  Search for "Everything you need to know about chains" right here on this forum.
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The only experience I have had with worn front chainrings is that the chain hooks on the worn tooth and you get a chainsuck type effect - sometimes it hooks till the tension of the rear derailleur pops it off.

So if you look back at the rear derailleur while pedalling you will see it getting pulled forward and the popping back.

This would happen no matter how hard you pedal.

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okay its happened to me aswell

 

Problem was my chainrings werent worn & it was only slipping from 7th,8th & 9th gear on the cassette when i applied force ie: standing & peddaling.

 

I then shortened my chain by 2 links & voila problems solved - no more slipping of the chain.

 

JB - perhaps you can assist me here, I would like to know on average how many links my chain should have. I have a long cage XT derailer, its 9spd & cant remember what the chainring figures are
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There is no average since bike chainstay lenghs vary quite a bit.

 

Make your chain so long that in the two biggest sprockets (big blade front, big sprocket rear), the jockey bends forward no more than 45 Degrees.

 

In the opposite two smallest, the jockey should not go back so much that it no longer exercises spring tension on your chain. That is the Zen spot.

 
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There is no average since bike chainstay lenghs vary quite a bit.

 

Make your chain so long that in the two biggest sprockets (big blade front' date=' big sprocket rear), the jockey bends forward no more than 45 Degrees.

 

In the opposite two smallest, the jockey should not go back so much that it no longer exercises spring tension on your chain. That is the Zen spot.

 
[/quote']

 

Wicked - thanks for that Johan. That was my logic initially & what i did. Only reason i asked is because it looks to me like the top derailer pulley wheel is getting really chowed up by the chain & is wearing very quickly, however i also need to add that they were/are very due for replacement but since i got the new chain & cassette its seems to have rapidly speeded up the process of wear. Nonetheless, its not really a major biggie for me as the pulley wheels are only a guide & replaceable which in my opinion dont contribute to major wear as the are only really a soft plasticky/rubbery compound.

 

I just thought that perhaps ive shortened the chain a bit too much, but since ive done pretty much what youve confirmed, I just think they were worn & with a new chain being put on, its speeded up the process as they are now in essence trying to "mould in" with the new parts which obviously is not going to work as they were already pretty much finished
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