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The rear mech on one of my bikes has become arthritic, as in the cage does not tension the chain properly when in the little ring and lower five cogs. I have sprayed with a dry ptfe lube and manipulated so it eases, but the problem comes back if not been on the bike for a week or two.

Anybody got any ideas how best to solve this apart from replacing or regular lubing.

Never had this before in a rear mech and been cycling for longer than I care to remember.

Thanks in advance.

7 comments

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bashthebox [752 posts] 3 years ago
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I had to get rid of a dura ace mech due to the same problem. Mind you, I just took the shop mechanic at his word that it was knackered, I've never had a go at fixing it. Maybe I should ask my new LBS for their opinion.

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Trull [81 posts] 3 years ago
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So no mention of which mech? Bike? What its used for? Just call me Harry Potter I'll wave my magic wand and give you the benefit of my 20 years of industrial engineering experience.

In related News - the Police have discovered an issue in the local area, involving an incident where an effect caused an issue locally. A local spokesman can neither confirm or deny this.  1

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FMOAB [289 posts] 3 years ago
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While I don't share the tetchiness of Trull, it is difficult to advise without knowing more.

I would advise taking it off the bike and saturating it in GT 85, or similar. Work the mech manually over the full ranges of its movement, soak again and leave it overnight in a bowl. Repeat the process, don't spare the penetrating oil and good luck.

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jason.timothy.jones [293 posts] 3 years ago
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there are a lot of 'it depends' to answer this, depending on Brand/model most are fairly easy to strip to a point of being able to repair/lubricate, if its beyond that it may be time to replace.

What make/model is it, i have a few exploded diagrams floating around that may help

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jason.timothy.jones [293 posts] 3 years ago
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MKultra [393 posts] 3 years ago
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Either your chain is too long or the mech has died, shimano mechs simply loose spring power once they get old enough.

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silly [39 posts] 3 years ago
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Thanks for all the advice. It is a dura-ace 7900 rear mech. Will keep trying with the penetrating oil in the hope it alleviates the problem.

May try the overhaul if it continues - though I have a bad habit of pulling things apart and not getting them back together properly!