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My bike has a set of Avid Elixir R hydraulic brakes. The front brake barely goes on when I pull the lever and the back brake feels pretty soft. I think I need to bleed them. How do I go about doing this?

I think the brakes got like this because I pressed the brake level when the bike was upside down or when the wheel was removed putting the bike into my car.

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All Avid brakes require the proprietary brake bleed equipment and that a fairly complex procedure is followed. Avid/SRAM sell a brake bleed kit that comprises:

  • two syringes
  • caliper and level hose barbs with hose and clamps
  • T10 Torx allen key
  • DOT 5.1 brake fluid
  • caliper spreaders to hold the caliper apart while bleeding

The kit is quite expensive and several eBay sellers provide a cheaper alternative kits. Any hydraulic brake fluid that complies with the DOT 5.1 standard is suitable for Avid brakes. It is possible to assemble your own brake bleed kit by sourcing some 20ml syringes, M? hose barbs, neoprene hose, hose clamps and using some US quarters or UK 2pence pieces to spread the calliper pistons.

The bleed procedure is documented by SRAM in a youtube video:

and also in their service manual PDF:

https://www.sram.com/service/techdocs/hydraulic-disc-brake-hose-length-adjustment-bleed-guide

The procedure involves:

  • prepare the brake fluid by using a partial vacuum to remove bubbles from the fluid
  • connect a 50% full syringe to the caliper and 25% full syringe to the lever
  • close the brake lever and clamp with a rubber band
  • pull on the caliper syringe gently to remove bubbles from the caliper
  • push the caliper syringe until around 25% of the fluid has transferred to the lever syringe
  • open the lever while gently applying pressure to the caliper
  • remove the caliper syringe and replace the bleed screw
  • pull gently on the level syringe to remove bubbles from the caliper
  • apply the brake lever and repeat until all bubbles are removed
  • remove the lever syringe and replace the bleed screw
  • clean all traces of brake fluid with alcohol or soapy water

At this point you should have properly bled brakes. Test carefully before heading back out on the trail!

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