December 26, 2005

    My wife bought a new mountain bike and we cannot figure out how to get the back breaks from squeaking when used. I tried break cleaner and towel and nothing. Any suggestions?


    First, I recommend a helpful book: the dictionary. Without one I couldn’t write about this stuff, and it looks like you shouldn’t either.
    Next, process of elimination. Cuz you’ve got a new bike I wouldn’t suspect the bike has dirty wheel rims and brake pads, but just for yucks I’d clean ‘em first—which you say you’ve done. If you didn’t wipe off the insides of the brake pads (slide that rag between the pad and the rim and clean the pad like shining a shoe), do that.
    Another likely cause of squeak: Bad toeing. And I don’t mean biking while barefoot. When braking, the front part of the bike’s brake pads should contact the rim before the back part. In good lighting, look at the brake pads from above, then squeeze the brake lever. If it doesn’t toe correctly, take the bike to a bike shop (ideally, one at which you bought it) for correction. Or to DIY try Park Tools’ pages on brake repair (scroll down to PAD TOEING).

Mr Bike

October 26, 2009

    Thought you might like to hear of a guaranteed way to stop this irritation. It is caused by “stiction”—a relative of friction where the objects slide over reach other and “stick and release” at a very high frequency, hence the squeal.
    All bike brake blocks contain rubber, and natural use puts a thin film of rubber on the rim. Thin films are notoriously easily oxidized; when you oxidize rubber, the result is very sticky. (If you have ever come across “perished” rubber you know what I mean). In fact the thin film is almost identical in properties to contact cement or adhesive.
    Because it is oxidized, the film dissolves only in a limited range of solvents, typically those found in cellulose paint thinners. Simply cleaning the rims rarely works, but I can guarantee success if you use xylene on a paper pad, and if you can't get that, then any cellulose thinners from your local auto accessory shop.

Frank M.

    Thanks, Frank. Tho I wish you'd stop sending bikers to auto stores.     Anyway. Other names for cellulose thinners: acetone, toluene, and methylbenzene. Consistent with the fact that you'll probably find this stuff in stores that sell automotive paint, some consider it environmentally nasty.

Mr Bike

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