I got caught in a rain storm yesterday, noticed my rear brake wasn't catching well in the rain, got home and dried everything off and the rear wheel/dropouts were completely black-streaked, covered in some kind of oily sludge. Tried to dissolve it with rubbing alcohol but there wasn't enough. The pads look to have been fouled so I'm going to swap those out (I don't think washing them will do the trick, will it?). I re-lubed the chain twice and the RD. I'm going to hose down and scrub everything this weekend, but where on earth did all this oil come from?!

This stuff obviously came from my bike, since the front wheel is fine. I don't think I ran through any oil puddles although that's a possibility.

  • It could be road grit thrown up by the front tire against the rest of the bike. If it's been dry for a while you'll get a lot of fine, gritty (and possibly oily) dark sludge off the road. (Brake dust, etc.) One rainy day in Belgium the roads were so dirty my chain seized up twice. – DavidW Jun 20 '19 at 14:59
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    Could you make your question more central? Are you asking how to clean the brake pads? If so, please share what kind of brakes you have. – Superman.Lopez Jun 20 '19 at 15:02
  • @Superman.Lopez OP is asking where all the oily sludge came from – Argenti Apparatus Jun 20 '19 at 16:12

The oily sludge likely came from the road, the front wheel threw it up on the the rear half of the bike, but avoided the spray itself.

Use a degreaser product to clean you bike thoroughly, paying special attention to the rims. I find a generic citrus degreaser works well but you can also use a bicycle specific one.

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