Chain keeps coming ...
 

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[Closed] Chain keeps coming off top jockey wheel

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On a 3 hour ride around Gisburn Forest the chain came off the top jockey wheel 3 times. Same again the next weekend at Antur Stiniog. The bike is pretty much brand new so it can't be a worn jockey wheel. Anybody know what might cause this? TIA


 
Posted : 08/09/2021 1:27 pm
 StuF
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Sram or shimano?
If Sram has the narrow / wide meshed properly with the chain?

I recently had it that the bolt holding the jockey wheel had come loose allowing the cage to be further apart and allowing the chain to drop off - although that's on an old mech


 
Posted : 08/09/2021 1:54 pm
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It's Shimano. I'll check the bolt/cage to ensure nothing has come loose. Thanks.


 
Posted : 08/09/2021 2:08 pm
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Bent mech arm or hanger can cause this too.


 
Posted : 08/09/2021 2:16 pm
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Floating/fixed jockey wheels installed the wrong way round from new? (Is the floating jockey wheel still even a thing? Not had to replace any for yonks).


 
Posted : 08/09/2021 2:38 pm
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I've had the issue quite a bit with 12 speed shimano mechs, the cage plates are made of brie, brie that has been left in the sun for a long time. Check that the top inner cage by the jockey wheel isn't bent a lot leaving too much space, close the gap up (it'll bend using only fingers).


 
Posted : 08/09/2021 5:06 pm
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I’m having this with an SLX 12s mech. Driving me frickin’ mental.
It’s been suggested to me that it might be something to do with the clutch not ‘clutching’ all the time.


 
Posted : 08/09/2021 6:16 pm
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Had this with sly 12 speed. In the end the rear (closest to wheel) side of the cage was snapped causing it to bend. Once replaced it was fine. A friend had a crash and bent his slightly and it started doing the same so that’s where I would start


 
Posted : 08/09/2021 8:03 pm
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Yep I've had 3 slx mechs 12 sped do this now. Just shite. Bending the cage back doesn't seem to fix it. Replacement cages out of stock everywhere so trying an xt mech as needed for a wales trip to see if that fixes issue.

Does anyone know if the xt cage fits slx mech if it does?


 
Posted : 08/09/2021 10:00 pm
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I had this, it got fixed when a load of bracken got stuck in the mech and ripped the rear of the cage out. Put in a new mech and it's all fine.

Not a cheap option and stressful halfway through a weekend away but effective.


 
Posted : 08/09/2021 10:47 pm
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I had same with SLX 12spd - now sorted with a (steel) Deore inner plate and third party top jockey (that seems to have more material just under teeth that likely stops chain dropping into gap).


 
Posted : 09/09/2021 11:02 am

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