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.
Closeup of brake lever contact adjuster being turned counterclockwise by hand

Turn contact adjuster until clicking stops

SBC-1 being held across center of handlebar and tip of brake lever to measure distance

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 lever on flat handlebars prepped with syringe holder and rag

Lever prepped with syringe holder and rag

PP-1.2 being used to spread brake pads in hydraulic caliper in preparation for bleed blocks

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.
Rear brake caliper unmounted from bike and hanging off of frame to position hose at angle
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.
Removing clip and unthreading pin from hydraulic brake caliper with threaded pin

threaded pad pin: remove clip and unthread pin

Bending cotter pin to remove from hydraulic brake caliper

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.
Removing brake pads from hydraulic brake caliper by hand

Two bleed blocks installed into a hydraulic brake caliper on a rigid bicycle fork

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.
Hose being finger threaded into brake bleeding syringe

Thread double-ended hoses into syringes

Finger threading adaptor #2618 onto syringe hose

Thread adaptors #2618 onto hoses

  1. Fill one syringe 1/4 full. This will be the lever syringe.
Brake bleeding syringe using hose to draw hydraulic brake fluid out of a container
  1. Hold the hose end up and push the syringe. Eliminate as much air as possible. Clip the hose.
Syringe being held upside down with hose lifted up to allow bubbles to escape

Hold syringe upright

Rag being held against syringe hose end while pushing out air bubbles

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.
Closeup of O-ring on bleed bolt after removed from brake lever bleed port

Ensure that o-ring is removed along with bleed screw

Adaptor end of syringe hose being installed into brake lever bleed port

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.
Bleed syringe being secured in syringe holder on flat handlbars

Adaptor end of bleed syringe being installed into bleed port of brake caliper

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.
Side by side of upper and lower bleed syringes, both being held upright
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.

Closeup of bleed syringe with dirty fluid entering
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.
Toe strap being secured around brake lever and flat handlebar to hold lever in place

hold brake lever down with toe strap or similar

Bleed syringe being held in hand and the plunger pushed, then pulled

push then pull on syringe

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

Closeup of bubbles in hose end at brake caliper bleed port
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.
Side-by-side images with one hand releasing the brake lever while another depresses the plunger on a syringe
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.
Bleed syringe being held in hand and the plunger pulled, then pushed
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.
Closeup of air bubbles in syringe hose end at brake lever bleed port
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 lever being sprayed with rubbing alcohol, especially around bleed port

Spray each component with alcohol

Hydraulic disc brake caliper on rigid bicycle fork being wiped with a clean rag

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.
Bleed syringe being held with two hands with the hose end emptying used fluid into a waste container

Empty spent fluid into appropriate container

A bleed syringe held in one hand and hose end in the other, working alcohol back and forth

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.
Threaded hose end being sprayed with rubbing alcohol

Thoroughly clean all threaded ends

Bleed syringe with plunger removed, with clean rag inserted into the body for cleaning

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)