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Metal shavings on rear dropout
#1
To be honest, I don't know which category this belongs in. Probably wheels and hubs, now that I think about it. Anyway, my girlfriend was complaining of sloppy shifting on her bike, so since she skipped the country for a few days (without me, I might add...), I figured I'd take a look at it for her. Right off the bat I found that the derailleur hanger was loose, so I tightened that up. Then I noticed that there was a ton of grease on the inside of the rear drive side dropout that looked like it had some kind of fabric threads in it. When I started wiping it up I discovered that the threads are metal shavings, and I'm not sure where they're coming from. I suspect they're either from stripped threads in the nut that holds the derailleur hanger to the frame, or from the fretting that had to have been happening from shifting with a loose hanger, but I have a feeling there might be something messed up in the freehub body because of all the grease on the dropout. There's a little bit of grease on the end of the freehub, too. Has anyone ever run into anything like this?
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#2
Re: the grease
Hubs (well, bearings in general) can / will loose grease when it is warm. They also loose grease if you put way too much into it (which I tend to do, better than running dry). You can just clean it up or take a look at the bearings (easy if it is cup and cone bearings, but check that first!).

Re: metal shavings
No idea. Your guess sounds alright to me
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#3
The guys at the Trek store said the metal shavings were from the chain and the cassette wearing down. I've never seen it that pronounced, I guess. They also said that the blob of grease was just extra chain lube that has collected there throughout the year. I don't really know how well my girlfriend takes care of her bike, so I guess this is possible.
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#4
Metal shavings from the chain and cassette? I haven't seen this (yet) and find it hard to believe. The wear should leave more like a metallic residue because chain and cassette wear are more like a slow abrasive process with a suspension of particles (sand etc) in oil. Since I do not really know how the shavings look like they still might be correct (even if I find this explanation really weird).
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