Brake Bleeding for SRAM Hydraulic Brakes Using the BKD-1

This article will review the bleeding procedure for SRAM hydraulic brakes while using the Park Tool BKD-1 Bleed Kit.

1

Preliminary Info

This bleeding procedure will work on SRAM drop bar and flat bar brakes that do not feature Bleeding Edge. See this article for the Bleeding Edge procedure.

Brake bleeding is considered an advanced service procedure, and requires a thorough technical knowledge of the braking system. If in doubt, or if this procedure is not working, contact the brake manufacturer for model-specific information.

It is important to always use the appropriate brake fluid for the brake being serviced. Never use mineral oil in brakes designed for DOT brake fluid, or vice versa. Never share bleed kits between DOT fluid and mineral oil systems. Mixing fluids can cause damage to components and lead to brake failure, which is dangerous.

DOT fluid is corrosive, and it can irritate the skin and eyes, and damage paint and other finishes - so it is important to take care. Wear gloves and eye protection during this procedure. Have plenty of rags handy for wiping up spills as quick as possible. Isopropyl alchohol is a good cleaner to help clean and neutralize the DOT fluid, if spilled. You may want to also cover your work area to avoid getting fluid on the floor.Dispose of any spent fluid in accordance with your local waste disposal authorities

2

Bicycle Prep

  1. Install the bike in a repair stand if available.

  2. Begin by prepping the lever.
    • If your flat bar lever is equipped with a contact adjuster, turn it opposite the arrow until it stops.
    • Measure the amount of reach from the centerline of the handlebar to the tip of the brake lever. To bleed it needs to be between 75mm and 80mm. if not, make note of your current adjustment and then adjust to between 75mm and 80mm. On some models, this is a tool-free adjustment, while other models require a hex wrench.
Brake Bleeding Flat Bar Adjuster

Turn contact adjuster until clicking stops

Brake Bleeding Flat Bar Reach Measurement

Tip of lever should fall between 75-80mm from center of handlebar

  1. Tie a rag around the lever to catch any spills.
  2. Attach the syringe holder to the handlebar.
  3. Remove the wheel.
  4. Use a pad spreader such as the PP-1.2 to push the pads back to allow for the bleed blocks once the pads are removed.
Brake Bleeding SRAM Prepped Lever 2

Lever prepped with syringe holder and rag

Brake Bleeding SRAM PP 1 2

spread pads to allow for bleed blocks

  1. Angle the bike in the stand so that the path of the hose from the caliper to the lever is consistently traveling upwards. It can also help to remove the caliper and let it hang, especially for rear calipers. This makes the path for air bubbles as easy as possible to follow.
Brake Bleeding SRAM Hose Direction

Position bike and caliper to minimize downward or lateral travel of brake hose

  1. The pads are removed to prevent any contamination.
    1. Remove the pad pin clip with a needlenose pliers, and unthread the pad pin with a 2.5mm hex wrench.
    2. For pads with a split cotter pin, use a needlenose pliers to straighten the pin, then pull it out.
Brake Bleeding SRAM Pad Pin 2

threaded pad pin: remove clip and unthread pin

Brake Bleeding SRAM Cotter Pin

cotter pin: bend pin straight and remove

  1. Pull the pads out. It can help to push from the bottom initially.
  2. install the bleed block and secure with either the pad pin, a rubber band or a zip tie.
    1. If the caliper has two sets of pistons, use both bleed blocks.
Brake Bleeding SRAM Pad Removal

Brake Bleeding SRAM Bleed Blocks

3

Bleed Kit Prep

  1. Install the double ended hoses onto the syringes, with the o ring capture away from the syringe.
  2. Install the red adaptor ends (part #2618) onto the syringe hoses.
Brake Bleeding SRAM Syringe Attachment

Thread double-ended hoses into syringes

Brake Bleeding SRAM Adapter

Thread adaptors #2618 onto hoses

  1. Fill one syringe 1/4 full. This will be the lever syringe.
Brake Bleeding SRAM Quarter Syringe

  1. Hold the hose end up and push the syringe. Eliminate as much air as possible. Clip the hose.
Brake Bleeding SRAM Eliminate Air 1

Hold syringe upright

Brake Bleeding SRAM Eliminate Air 2

push until no air remains in hose

  1. Fill the second syringe 3/4 full. This will be the caliper syringe.
  2. Repeat the process of eliminating air from the hose and clipping the hose.
  3. Remove the bleed screw from the lever using a Torx®-compatible T10 wrench. There is an o-ring on this screw - make sure it also comes out.
  4. Install the 1/4 full syringe into the lever. Ensure the o-ring is seated fully and evenly in the capture of the bleed port as you thread in the adapter. Clean up any spilled fluid right away.
Brake Bleeding SRAM Bleed Screw O Ring

Ensure that o-ring is removed along with bleed screw

Brake Bleeding SRAM Lever Syringe Installation

fully thread syringe into bleed port

  1. Install the syringe in the holder.
  2. Remove the caliper bleed screw and install the 3/4 full caliper syringe into the bleed port.
Brake Bleeding SRAM Syringe Holder

Brake Bleeding SRAM Caliper Syringe Installation

4

Bleeding

  1. Unclip both syringes.
  2. Hold the caliper syringe tip down and push fresh fluid into the system. As you push fluid into the system it will push excess fluid into the lever syringe.
Brake Bleeding Begin

Ensure both syringes are upright to allow free flow of fluid and air bubbles

NOTE: If the fluid coming out is dirty or discolored, push all fluid to the lever syringe, remove the syringes, refill and start the bleeding process over. This will ensure that you brake system has clean fresh fluid.

Brake Bleeding SRAM Dirty Fluid

Dirty fluid entering syringe

  1. Once the lever syringe is 3/4 full and the caliper syringe is about 1/4 full, close the clip on the lever syringe.
  2. Pull the brake lever and hold it down with a toe strap, rubber band, or other suitable option.
  3. Push, then pull, on the caliper syringe to create a vacuum.
Brake Bleeding Toe Strap Lever

hold brake lever down with toe strap or similar

Brake Bleeding Push Then Pull

push then pull on syringe

Once the vacuum is created you may see a few bubbles working their way out of the caliper.

Brake Bleeding Bubbles from Caliper

bubbles escaping caliper

  1. Continue the back-and-forth of pushing on the syringe to create pressure, then pulling on the syringe to create a vacuum again, until no more bubbles come from the caliper.
  2. Undo the toe strap or other holder while holding the lever. Then slowly release the lever while pushing on the caliper syringe.
Brake Bleeding Release Lever

push on caliper syringe while releasing lever

  1. Clip the caliper syringe hose, and remove the caliper syringe.
  2. Quickly reinstall the bleed port screw and clean up any spilled liquid.
  3. At the lever, unclip the syringe clip to allow fluid movement. Pull on the syringe to create a vacuum, drawing air out of the system. Then pressurize by pushing on the syringe.
Brake Bleeding Pull Then Push

pull then push on syringe

  1. Let the syringe equalize and then pull and release the brake lever 10 times. Repeat these steps until there are no more bubbles.
Brake Bleeding SRAM Lever Bubbles

bubbles escaping lever

  1. Push on the syringe, release the syringe to equalize, and you are ready to clip the hose, remove the syringe and replace the bleed port screw.
5

Reset Bicycle

  1. Remove the bleed blocks.
  2. Clean the caliper body, lever, and surrounding areas with alcohol and rags.
Brake Bleeding SRAM spray alcohol

Spray each component with alcohol

Brake Bleeding SRAM Wipe Caliper

Wipe each component thoroughly

  1. Reinstall the pads, pad pin and clip.
  2. If you removed the caliper, reinstall it.
  3. Reinstall the wheel.
  4. Reset the lever reach back to the desired setting and pull the brake lever 3 times. This will self adjust the system to the pad life that is left.

NOTE: If you encounter rubbing, you may need to realign your calipers at this time.

6

Clean Kit

  1. After bleeding, clear the syringes and hoses of all fluid.
  2. To prolong the life of your bleed kit, it’s recommended to clean the whole system with alcohol. Start by running alcohol through the hoses.
Brake Bleeding Empty Syringes

Empty spent fluid into appropriate container

Brake Bleeding SRAM Cleaning Alcohol Syringe Assembly

pour alcohol into syringe assembly and run back and forth

  1. Disassemble the kit and wipe down each piece, especially the parts that came into contact with DOT fluid.
Brake Bleeding SRAM Cleaning Spray Hose End

Thoroughly clean all threaded ends

Brake Bleeding SRAM Cleaning Wipe Syringe

Thoroughly wipe all surfaces

  1. Leave the kit out to dry.
  2. Dispose of fluid in accordance with local regulations (see resources for: US, UK)