Idlers and chain coming off

Joined
Oct 14, 2020
Messages
62
Location
Broken Arrow, Oklahoma
Any good fixes, the chain continually came off today, do I need to shorten the chain, I have a mountain bike set of 3 chain rings, is there a guard, would a deeper idler pulley groove work better?
 
Joined
Oct 19, 2012
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1,331
Location
Wakefield, UK
What part of the system is the chain coming off? Typically idler pulleys would have a retainer to go with them, something like this:-

 
Joined
Oct 14, 2020
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62
Location
Broken Arrow, Oklahoma
Your chain is deeper into the pulley, I have thought about a guard over it but my chain isnt that deep into the pulley. Old pic, I have cleaned the chain
 
Joined
Oct 19, 2012
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1,331
Location
Wakefield, UK
It's just a picture off the 'net - not mine. Mine are deep in though. If you want to make a deeper groove in a nylon pulley you can usually fasten it in a drill and use a wood chisel like a poor man's lathe. Even with a deep groove you need a retainer.
 
Joined
Sep 16, 2018
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Netherlands
I think that, that system is enough. I made something like that to kerp my chain on. It also came off. That prevents it very well.
 
Joined
Feb 7, 2008
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Location
Nottinghamshire England
You never answered this question ?

What part of the system is the chain coming off?
If it is the pulley just add some cheeks to your pulley till it is that deep ?

Aluminium or plywood is suitable , then add a keeper as shown.
 
Joined
Feb 7, 2008
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2,951
Location
Nottinghamshire England
Just asked because sometimes it can come off the front chain rings.

A common cause is if you are just free wheeling and you go over a bump , with the weight of that amount of chain moving up and down it can come off the top of the pulleys/chain rings or move outside the groove where it passes underneath.

Another common cause is a stiff link , usually where you have joined the chains together ? as I guess you have 2.5 - 3 chains joined together that would show whilst pedalling ?

If you don't want side cheeks and keepers on the pulleys another way of doing chain management is a small length of chain tube on both the approach and exit of each pulley ?

Also what is the diameter of the pulleys ? on the drive side the bigger the diameter the less resistance they will introduce and the easier it is to make a deep grove ?

It is not clear from the picture however it looks like 1 idler between the existing 2 could replace both of them ? the less idlers in the drive side the better ?

As this problem just started or has it been apparent from the day it was first ridden ?

all the best Paul

ps I am a Delta man so some of the above is hearsay and not been experienced by me ...
I am sure a bona fide tadpole man will be along shortly (y);)
 
Joined
Feb 20, 2013
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Axedale, Victoria, Australia
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axerail.coffeecup.com
Other than problems with the chain itself, chain jumping can only be caused by chain alignment issues - whatever their cause at any particular time. This includes "floppy" chain and bumps.

Check the chain angle in each gear to see that it sits easily on the sprocket teeth. If it doesn't, a jump is waiting to happen and may only occur when the drive is under additional strain while going up hill.

If your problem only occurs when using the highest or the lowest gear, it is due to derailleur alignment. By the way, your recent pic or video is only a non-accessible button here.
 
Joined
Feb 7, 2008
Messages
2,951
Location
Nottinghamshire England
By the way, your recent pic or video is only a non-accessible button here.


I assume he is referring to this picture ? not a great help as the chain is not ' on' and you can't see what is happening on the other side of the bars ?
 
Joined
Oct 14, 2020
Messages
62
Location
Broken Arrow, Oklahoma
Other than problems with the chain itself, chain jumping can only be caused by chain alignment issues - whatever their cause at any particular time. This includes "floppy" chain and bumps.

Check the chain angle in each gear to see that it sits easily on the sprocket teeth. If it doesn't, a jump is waiting to happen and may only occur when the drive is under additional strain while going up hill.

If your problem only occurs when using the highest or the lowest gear, it is due to derailleur alignment. By the way, your recent pic or video is only a non-accessible button here.
I think floppy chain is the problem, might take a few more link's out.
 

Twinkle

Super Moderator
Joined
Apr 14, 2013
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Location
Peacehaven nr Brighton, Sussex ,UK
Wondered about a tention idler between the two also
That can cause other chain tensioning problems, we have used a deeper cut pulley and guide on all our tadpole builds , never had a chain derail, front , middle or back !
Have also tried chain guide tubes for the first time on the current build .
 
Joined
Oct 14, 2020
Messages
62
Location
Broken Arrow, Oklahoma
That can cause other chain tensioning problems, we have used a deeper cut pulley and guide on all our tadpole builds , never had a chain derail, front , middle or back !
Have also tried chain guide tubes for the first time on the current build .
Have been looking into chain guard's
 
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