chain jams; pushes FD up
08-23-22, 03:37 PM
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chain jams; pushes FD up
Riding the Masi yesterday, bout 40 miles in, everything going great, suddenly FD is jammed. I figured out what happened: when I shift from middle ring to big > chain does not mesh w/ring per usual, instead it sits on top of ring > when chain enters cage of FD, jams, pushes FD up seat tube. This is the 2ND TIME this has happened in the last cpl weeks. FD, SL & rings are alivio; chain is sram. None of the components are anywhere near the end of their life. I have absolutely no idea where this came from- everything has been working fine since day 1. pls help
08-23-22, 06:22 PM
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Photos. Photos. Photos.
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08-23-22, 06:24 PM
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Had a similar issue with the below shown RD during an 'out of spec' setup. Chainring was larger than intended for. On the mis-shifts, the chain would jam against the tab at the front of the cage (red arrow).
Moved the FD up to prevent it from jamming. Outer cage is 5-6mm above the large ring instead of the usual 1-3mm. Not the best solution, but works well enough for now. Final build will use a different FD.
Moved the FD up to prevent it from jamming. Outer cage is 5-6mm above the large ring instead of the usual 1-3mm. Not the best solution, but works well enough for now. Final build will use a different FD.
08-24-22, 03:39 PM
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Had a similar issue with the below shown RD during an 'out of spec' setup. Chainring was larger than intended for. On the mis-shifts, the chain would jam against the tab at the front of the cage (red arrow).
Moved the FD up to prevent it from jamming. Outer cage is 5-6mm above the large ring instead of the usual 1-3mm. Not the best solution, but works well enough for now. Final build will use a different FD.
Moved the FD up to prevent it from jamming. Outer cage is 5-6mm above the large ring instead of the usual 1-3mm. Not the best solution, but works well enough for now. Final build will use a different FD.
For now, Im gonna replace cable & chain. (tmrw)
08-24-22, 03:57 PM
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Seems that your FD has the tab in the very front of the cage. Looks like its bent upwards, probably from the mis-shifts. Not sure why you're getting the mis-shifts to begin with.
If you're changing the cable, a check of the condition of the cable housing and end caps may be in order.
08-24-22, 04:04 PM
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Yes, big oops there.
Seems that your FD has the tab in the very front of the cage. Looks like its bent upwards, probably from the mis-shifts. Not sure why you're getting the mis-shifts to begin with.
If you're changing the cable, a check of the condition of the cable housing and end caps may be in order.
Seems that your FD has the tab in the very front of the cage. Looks like its bent upwards, probably from the mis-shifts. Not sure why you're getting the mis-shifts to begin with.
If you're changing the cable, a check of the condition of the cable housing and end caps may be in order.
The only thing I can think of is a bad link running into a bad tooth
08-24-22, 07:11 PM
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First is the large amount of tooth wear on the big and small rings (can't see the middle teeth...). These will in time cause more issues so start budgeting for their replacement.
The current (in the photos provided) ft der cage height above the large ring is way way too much. When the cage outer plate is just coplaner/above to the large ring the gap between the teeth tops and cage plate lower edge will be 2-4mms.
It is possible given the wear I see that the ft der cage could have a groove worn/cut into the plate's inside surfaces. This would cause chain jamming during shifting (and Shimano MtB shifters generally don't have a trim feature, so chain rub is more common than on their road stuff).
The der should be able to be tightened around the seat tube well enough to not move or travel up the ST from the stress of poor shifting. Often once a shifting jam has happened the outer cage plate will distort and no longer have that 2-4mm gap above the teeth.
I hope we can assume you never shift the ft under any pedal pressure
Andy
The current (in the photos provided) ft der cage height above the large ring is way way too much. When the cage outer plate is just coplaner/above to the large ring the gap between the teeth tops and cage plate lower edge will be 2-4mms.
It is possible given the wear I see that the ft der cage could have a groove worn/cut into the plate's inside surfaces. This would cause chain jamming during shifting (and Shimano MtB shifters generally don't have a trim feature, so chain rub is more common than on their road stuff).
The der should be able to be tightened around the seat tube well enough to not move or travel up the ST from the stress of poor shifting. Often once a shifting jam has happened the outer cage plate will distort and no longer have that 2-4mm gap above the teeth.
I hope we can assume you never shift the ft under any pedal pressure
Andy
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08-24-22, 07:27 PM
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Andy said it best also that cable is super frayed so I have to imagine the bike is not as well cared for as it could be seeing that. Take care of the bike and it will take care of you, maltreat it and you can easily run into problems.
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08-25-22, 08:36 AM
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Oh my is that worn, replacement is the best solution. New rings, chain, and cassette. Andrew has already mentioned the position of the derailleur, and the possibility of shifting techniques may be in play, but those parts are well past.
08-25-22, 03:33 PM
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ty all for comments.
The above pics are of after the incident- after the FD had been jammed up the seat tube, idk, 1/8" or more. The CS & chain were replaced spring of this year. The chainrings a cpl yrs ago.
So, below are recent pics after chain & cable replaced. The old chain was worn around 1/8" over the entire length. The guy @ lbs said bring the bike in/it could be many things/something is out of adjustment. Well, Im gonna ride it Saturday/Ill find out how it works.
shown in 1st gear.
The above pics are of after the incident- after the FD had been jammed up the seat tube, idk, 1/8" or more. The CS & chain were replaced spring of this year. The chainrings a cpl yrs ago.
So, below are recent pics after chain & cable replaced. The old chain was worn around 1/8" over the entire length. The guy @ lbs said bring the bike in/it could be many things/something is out of adjustment. Well, Im gonna ride it Saturday/Ill find out how it works.
shown in 1st gear.
