Tips on bleeding moto brake calipers

May 15, 2026

Hydraulic Brakes Overview

Bleeding brakes requires patience and understanding of the hydraulic system. First we start with an overview of how a hydraulic brake system works:

1. Lever/Pedal Input: You squeeze the handlebar lever (front) or press the foot pedal (rear).
2. Fluid Pressurization: This mechanical pull pushes a tiny piston inside the handlebar or foot master cylinder, forcing brake fluid down the lines.
3. Line Travel: The fluid travels down reinforced lines (often braided stainless steel on high-performance bikes to prevent line expansion).
4. Caliper Action: The fluid enters the brake caliper mounted to the wheel fork or swingarm. It pushes one or more large pistons inward.
5. The Stop: The pistons clamp the brake pads against the spinning brake rotor (disc). Kinetic energy turns into heat, and the bike slows down.

Now, here are some steps and tips to getting a good initial bleed on your brakes:

1. Step one is to make sure your hydraulic lines are firmly tightened down on both the caliper and the lever/master cylinder sides. Give it a real firm tightening.

2. When installing a new caliper, you need to first understand that the system is empty of any Dot 4 fluid. Trying to fill the system from the lever reservoir will take too much time and is not efficient. Therefore, start at the caliper side.

3. You should have a bleeding syringe with flex tube in hand in order to bleed your brakes.

FILL FROM CALIPER

4. Start by filling the syringe with Dot4 brake fluid. Then attach it to the bleed nipple and loosen the bleed nipple maybe a ¼ turn. You will know when you have opened it enough when you starting pumping the fluid using your syringe into the system. Make sure you have the lever reservoir open. You can leave the black seal on but have it loose without the aluminum cover on. This allows the system to breath.

5. Slowly push the syringe pushing the fluid into the caliper. It may take 2 – 3 syringe fillings (depending on size of syringe) before you start seeing fluid in the reservoir.

6. Once the reservoir has filled, close the bleed screw.

BLEED FROM LEVER

7. Now empty the syringe, replace it on the bleed screw.

8. With the black seal on top of the reservoir (to prevent spraying out), pump the lever several times and keep the lever pressed in, open the bleed screw and you should start to see some fluid push back into the syringe. Close the bleed screw and let go of lever.

9. Repeat step 8 3 – 5 times until you start feeling pressure on the lever when you pump it and the bleed screw is closed.

10. Flick on the lever several times during this step starting on Step 7. This encourages bubbles to surface up. You can also tap on the caliper, and hose.

11. If the lever is still feeling soft, repeat from Step 4 and Step 5 – it will go quicker as the system is already full – you are just trying to eliminate any remaining bubbles.

12. If the brake is starting to feel pretty firm, try fulling putting the reservoir cap back on. This helps the pressure build. Repeat steps 4 – 10 as needed.