Logo for Blu Acciaio
  • Blu Acciaio Editor

From the workshop: brake bleeding

This is another article in our article series: "From the workshop". In these series we write brief notes on bicycle maintenance, ranging from wiring of dynamos to basic service of internal gear hubs. These articles will sometimes deal with the most obvious of maintenance tasks, but still we find them useful as reminders for our future selves, and perhaps also for some of you other amateur mechanics out there..


This article deals with brake bleeding and is mostly based on this excellent walkthrough from Performance Bicycle: https://www.youtube.com/watch?v=9ZYmW8i8TWQ


To complete this procedure you need but a few things: Shimano mineral oil, small flat screw driver to remove the pin locking the brake pads in position, big flat screw driver or similar to push pistons into the caliper, allen key, funnel, funnel adapter, funnel plunger, bleed block, wrench to control the bleed screw, strips, straps, syringe with hose and disposal canister with hose.

Tools of the trade for brake bleeding

In principle brake bleeding is quite simple and straight forward. But often we dont manage to get all the air out of the brake system, which quite quickly will deteriorate braking performance. By following the steps below however, we seem to get the air out, and dont need to re-bleed for a long time. The exact items needed and their dimensions may vary across braking systems, but the procedure should be roughly the same.


1.

Reset all screws adjusting lever travel


2.

Remove brake pads


3.

Align pistons so they are flush with caliper body


4.

Insert the bleedblock. Different calipers require different bleed blocks, but it dont need to be a perfect fit, as long as it stays in place

Bleed block inserted in the caliper

5.

Adjust brake level at 45 degrees to the ground


6.

Remove bleed screw from brake lever, remember to include the o-ring


7.

Fit the bleed funnel finger tight to the bleed port on the brake lever

Some brake levers require an adapter to fit the standard funnel from Shimano

8.

Add a little bit of oil to the funnel to create an airlock


9.

Loosen brake caliper from frame. The bleed port must be the highest point to let air flow

out


10.

Fill the bleed syringe with oil. Fill slowly so the oil dont mix with air. Remember to use the correct oil for your brake system


11.

Remove the rubber cap from the bleed port of the caliper


12.

Attach the syringe to the bleed port of the caliper. Avoid inserting air, but not a big problem if you do. These bubbles will be dealt with later in the process

Ready to insert fresh oil into the system, preferably without new air bubbles..

13.

Open the screw controlling the bleed port of the caliper slightly and start pushing through the oil from the syringe


14.

Keep an eye out for air bubbles in the funnel. When no more air bubbles appear, close the bleed

screw on the caliper and then remove the syringe from the bleed port


15.

Fit the oil disposal canister to the bleed port of the caliper and again slightly open the screw controlling the bleed port


16.

Fill the funnel with oil and pump the brake lever gently a few times. While doing so, tap

the brake hose and caliper to break loose any air bubbles that might remain in the brake system. This is easier said than done if your cables are routed internally

Oil disposal canister fitted to the bleed port of the caliper

17.

When no more bubbles can be seen from the oil flowing to the disposal canister, close the screw controlling the bleed port of the caliper. Do not yet remove the canister


18.

Check that the funnel still has sufficient oil to create an airlock, iIf necessary add more


19.

Apply pressure the brake lever and secure it with a strap, so it remains in a squeezed position

Voile Straps are excellent for applying pressure to the brake lever while you are working the bleed screw

20.

Open and close the screw controlling the bleed port of the caliper in rapid succession as to get out any remaining air


21.

Remove disposal canister


22.

Refit the rubber cap on the bleed port of the caliper


23.

Remove the pressure strap on the lever


24.

Squeeze the lever once again to exit trapped air


25.

Adjust the angle so the lever points slightly upward and squeeze the lever


26.

Adjust angle 45 degrees down again and squeeze the lever


27.

Repeat 24-26 until no more bubbles can be seen


28.

Level the funnel and insert the funnel plunger before removing it frem the brake lever


29.

Top of the reservoir of the brake level with oil and refit the o-ring and screw


30.

Return lever to original position


31.

Remove bleed block


32.

Clean caliper and refit to frame, but leave loose for later adjustment. Insert and secure the brake pads. Make sure to not let any brake fluid come in contact with the brake pads or the brake rotor


33.

Squeeze the brake lever a few times to center the pads and then squeeze and hold the

lever while tightening the caliper to the frame to center it on the rotor



#brakebleeding #bleedkit #shimano

22 views