Noise and vibration from rear mech.
davecooper
Posts: 290
Completely rebuilt bike last year and used it on a trainer over the winter. The only things I changed on the transmission was the chainset, chain and bottom bracket bearing. All these were of a similar spec to the originals. The rear mech and cassette had only seen a couple of thousand miles at the most. The chainset is a Tiagra triple, the rear mech is a Tiagra 9 speed but with 8 speed levers and cassette. The chain is an HG40 which is supposedly an 8 speed but apparently will work fine with a 9 speed mech.
Although it seemed fine on the middle ring and the middle few sprockets, as I dropped toward the smallest sprocket there appeared to be a lot of vibration and the occasional clunk from the rear mech area. It is at its worst when on the big ring and the smallest sprocket and it sounds and feels awful, almost as if there are meshing problems or the chain is fouling somewhere. I have also realised that it is slightly apparent on the larger sprockets but gets worse as you move towerd the smaller ones.
I have checked everything, chainline, jockey wheels (which I found where initially in the wrong positions), clearance between cage and chain and clearance between jockey wheels and sprockets, cage not bent etc. I cannot see any problems. If I move the cage while pedalling (by hand) it makes no difference either. I am lost as to what is causing this. Any help would be greatly appreciated.
Although it seemed fine on the middle ring and the middle few sprockets, as I dropped toward the smallest sprocket there appeared to be a lot of vibration and the occasional clunk from the rear mech area. It is at its worst when on the big ring and the smallest sprocket and it sounds and feels awful, almost as if there are meshing problems or the chain is fouling somewhere. I have also realised that it is slightly apparent on the larger sprockets but gets worse as you move towerd the smaller ones.
I have checked everything, chainline, jockey wheels (which I found where initially in the wrong positions), clearance between cage and chain and clearance between jockey wheels and sprockets, cage not bent etc. I cannot see any problems. If I move the cage while pedalling (by hand) it makes no difference either. I am lost as to what is causing this. Any help would be greatly appreciated.
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Comments
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Is the chain correctly routed through the rear mech? I have on occasion managed to mis-thread one so it's fouling the little tab that's meant to keep the chain on the jockey wheel.
Is the chain the correct length? The fact that it's noisier in the smaller sprockets suggests it could be too long, but the observation that this is worse in the big chainring suggests the opposite.
As always, photos might help...0 -
I will check the routing and I will take some photos. Thanks.0
