How to bleed Shimano mountain bike disc brakes?

How to bleed Shimano mountain bike disc brakes?

For MTB hydraulic brakes that use mineral brake fluid, bleeding is necessary if you feel a loss of performance. Here's how to do it yourself on your ATV.

  • Time: 1h00
  • Level : Difficult
  • Tools : Purge kit / Mineral fluid / 2.5 mm Allen wrench / 7 mm open-end wrench / Screwdriver


Steps

Reminder: Depending on the brake model, the procedure may change. It's best to consult the manufacturer's manual beforehand.

  1. Replace pads with the bleed wedge.

  2. Position the brake lever at 45° to the horizontal.

  3. Remove the bleed screw from the lever, then fit the funnel without the stem/cap.

  4. Place the syringe, previously filled with at least 10 ml of mineral liquid, onto the bleed screw on the caliper.

  5. Open the bleed screw with the wrench, then drain the circuit by pressing on the syringe. The liquid will flow back up through the funnel.

  6. Temporarily close the bleed screw when you can no longer see bubbles coming out of the funnel, then remove the syringe from the caliper.

  7. Now place the hose with the collection bag on the caliper and open the bleed screw.

  8. Tap the caliper with the handle of a screwdriver to loosen the bubbles as the fluid flows out. Caution: during this operation, the level in the funnel will drop, so be sure to fill it with brake fluid to prevent air from entering the circuit.

  9. Temporarily close the bleed screw when no more bubbles are visible in the connected hose.

  10. Actuate and hold the brake lever, then quickly open and close the bleed screw several times (for about half a second each time) to evacuate any remaining air bubbles. Close the bleed screw before the lever reaches the end of its travel.

  11. Actuate the brake lever several times to force any bubbles back up into the funnel.
    Probikeshop tip: the lever should be or become hard at this stage.
  12. Position the lever horizontally, then repeat step 11.

  13. Remove the plugged funnel with the rod/plug.

  14. Replace the lever bleed screw.

  15. Wipe off all traces of oil.

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