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Avid DB1 brakes bleed.

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Avid DB1 brakes bleed.

Old 03-15-16, 04:11 PM
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Avid DB1 brakes bleed.

I have a mtn bike that has Avid DB1 brakes, the brake lever is soft, therefore, I think the brakes need bleeding. The person that owns the bike, tried to adjust the brakes, and now the rear brakes are not working. What do you suggest? Do I try and bleed the brakes? Can I use regular car brake fluid DOT4? or do I need special brake fluid for Avid brakes. Does anyone know how to bleed the brakes?
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Old 03-15-16, 04:50 PM
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Standard automotive DOT4 or DOT5.1 is fine. Use a sealed bottle if you don't have one that's been cracked open within the past month. Glycol based brake fluid is hygroscopic, so the longer it's exposed to air and humidity, the more moisture content it will have, which is bad.

To be fair, I'm not entirely certain why bicycle hydraulic brake systems don't use DOT5 silicone-based fluid. It's noncorrosive and hydrophobic.
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Old 03-16-16, 04:45 AM
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Some disc brake brands, notably Shimano, use mineral oil. All master cylinders (levers) specify which fluid to use, and that should not be deviated from. There are pro/cons associates with the different types of fluid. Note that virtually all motor vehicles use glycol based fluid, and for good reason. The main failing of hydrophic fluids is that any water that gets into the system remains separate, settles to the lowest point (the caliper) and can boil at much lower temperature than the brake fluid causing complete loss of braking. FWIW: I had this happen to me once on a racing motorcycle using DOT5.
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Old 03-16-16, 08:38 AM
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How to bleed Avid disc brakes by SRAM on youtube: https://www.bikeforums.net/general-cy...kes-bleed.html

If you want to buy a bleed kit you can get one for $15 here: Avid Disc Brake Bleed Kit Juicy Elixir Brakes Extra's USA | eBay

I own a trike with Hope C2 hydraulic disc brakes and have the bleed kit that came with it but never bothered to use it for the few times I had to bleed the brakes over a decade of use. More bother than it was worth. The SRAM kits include DOT 5.1 brake fluid so that is probably what you should use.
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