How to bleed shimano brakes

Shimano hydraulic disc brakes, amongst other popular brands, have completely changed the game for cyclists. They offer amazing stopping power and control on all kinds of terrain. But here’s the thing: if you want your Shimano brakes to work their best and keep you safe, you need to understand how to take care of them. That’s where the knowledge of how to bleed shimano brakes comes in. It’s a process that gets rid of air bubbles in the brake system. This makes sure your brakes stay strong and consistent.

In this easy-to-follow guide, we’re going to walk you through the basics of bleeding your Shimano disc brakes. You’ll find out what tools and materials you’ll need and give you step-by-step instructions. By the end, you’ll feel confident and capable of bleeding your Shimano brakes whenever they need a little TLC.

Remember, your brakes are crucial for your safety. By taking a little time to bleed your Shimano disc brakes, you’ll have the peace of mind that comes from knowing your brakes are working perfectly. So let’s get started and learn how to bleed your Shimano disc brakes. It’s a skill that’ll give you better braking and let you focus on the pure joy of riding.

What is a disc brake bleeding process?

It’s worth noting that brake maintenance isn’t just about cleaning and changing brake pads. Bleeding should be a regular part of your maintenance routine, especially if you’ve noticed any warning signs. If your brake lever feels mushy, if your braking power has decreased, or if your lever travels too far before engaging, it’s time to bleed those brakes. By bleeding them regularly, you’ll keep yourself safe and make sure your Shimano disc brakes perform their best.

Symptoms Indicating the Need for Brake Bleeding

Several symptoms may arise, indicating the need for brake bleeding:

• Soft or Mushy Lever Feel. If you notice that your brake lever feels spongy, it could be a sign of air in the brake system. When you apply the brakes, the lever may require more travel or feel less responsive.
• Decreased Braking Power. When air bubbles are present, they can reduce the overall braking power of the system. You might notice that it takes longer to slow down or stop. Also, the brakes may feel less effective even when fully engaged.
• Excessive Lever Travel. If you have to pull the brake lever farther than usual before the brakes engage, it could indicate the presence of air bubbles in the system. This extended lever travel affects the responsiveness and control of the brakes.
• Inconsistent Brake Performance. Air bubbles can cause the braking performance to be inconsistent, leading to variations in stopping power or modulation. This inconsistency can be unsettling and compromise your confidence while riding.

If you experience any of these symptoms, then it may be a good time to perform a brake bleeding procedure. This will eliminate the air bubbles and restore the optimal performance of your Shimano disc brakes.

List of Required Tools

To successfully bleed your Shimano disc brakes, you will need the following tools:

• Bike stand: This will securely hold your bike in place during the bleeding process.
• 2.5mm, 3mm, and 5mm Allen keys. These will be used to remove and tighten various brake components.
• Flathead screwdriver: You may need this to remove the pad axle and push the pistons back.
• Long nose pliers. These are useful for straightening and bending the end of the retaining split pin and removing and refitting the caliper spring clip onto the pad axle.
• 7mm spanner: This will be used to loosen and tighten the bleed screw.
• Bike oil funnel tool with oil stopper: This specialised tool attaches to the brake lever reservoir and allows you to accurately pour brake fluid into the system.
• Syringe. A syringe will be used to remove old brake fluid and inject fresh fluid into the system.
• Compatible transparent tubing. This tubing will be attached to the syringe and brake caliper to facilitate fluid transfer.
• Fluid bag or plastic bottle: You’ll need a container to collect the old brake fluid during the bleeding process.
• Bleed spacer: This handy tool replaces the brake pads and disc rotor, allowing you to safely bleed the brakes without damaging the pads.
• Mineral oil: Shimano recommends using its own branded brake fluid due to potential variations in quality and characteristics among different brands of mineral oil.
• Isopropyl alcohol: This is useful for cleaning brake components and ensuring a contaminant-free system.
• Cloth or paper towel: These will come in handy for wiping down brake parts and cleaning up any spills.
• Gloves: It’s essential to wear gloves to protect your hands from brake fluid and potential contaminants.
• Safety glasses: These will provide eye protection from any splashes or spills during the bleeding process.
• Velcro strap. A Velcro strap can be used to secure the brake lever in the fully engaged position, allowing for easier bleeding.

How to bleed shimano brakes – Preparation

To ensure a smooth process, follow these step-by-step instructions for preparing to bleed your Shimano disc brakes:

• Place the bike in a sturdy stand or secure it in a stable position for easy access to the brake system.
• Remove the front wheel. If you’re unsure how to do this, refer to our step-by-step front wheel removal tutorial for guidance.
• Take a screwdriver and position it between one brake pad and the piston. Gently push the pad against the other pad, which will force the piston back into the caliper. Repeat this process for the other side.

• If your brake pads are held in place with a pad axle, use long nose pliers to remove the small caliper spring clip.

• Then, using a 2.5mm Allen key or a flat-head screwdriver, remove the pad axle.

• If your brake pads are held in place with a retaining split pin, straighten the end of the pin using long nose pliers. Slide the pin out of the caliper.

• Remove the brake pads. Take care not to touch the braking surface, as the natural oils on your skin can contaminate the pads.

• Use a 5mm Allen key to position the brake lever in a horizontal orientation. This will help facilitate the bleeding process.

• Locate the upper bleed screw on the brake lever assembly and carefully remove it, along with the seal.

• On the caliper, locate the bleed nipple cap or the bleed port cap, depending on your brake model. Remove the cap to access the bleeding point.

• Connect the transparent tubing with an oil bag or bottle to the caliper’s bleed screw or bleed port.

• Secure it in place using a strap, ensuring a tight and leak-free connection.

How to bleed shimano brakes – Draining out the old oil

Over time the mineral oil can degrade when exposed to heat and pressure so it is important to replace it with a new one once in a while. The obvious sign is when the mineral oil becomes severely discoloured. If you need to change the mineral oil first perform the draining procedure.

• Loosen the bleed screw: Using a 7mm spanner or 3mm allen key, gently loosen the bleed screw by turning it about an eighth of a turn in an anticlockwise direction. This will allow the fluid to start coming out.

• Press and release the lever: To facilitate the draining process, press and release the brake lever repeatedly. This action helps in effectively draining the old mineral oil. Continue operating the lever until all the brake fluid has been drained out.
• Tighten the bleed screw. Once all the fluid has been drained, securely tighten the bleed screw using the 7mm spanner. Ensure that it is tightened properly to prevent any leakage.
• Prepare the area: To prevent any spills or drips, cover the area around the caliper bleed point with a paper towel or rag. This will help absorb any residual oil during the next steps.
• Remove the tubing with the oil bag or bottle. Disconnect the tubing that is connected to the caliper bleed point. Carefully remove it while ensuring that the oil bag or bottle is securely held to prevent any spills.
• Transfer the oil: Transfer the drained mineral oil from the oil bag or bottle to a separate container or bottle. This step ensures proper disposal or storage of the old oil.

How to bleed shimano brakes- Removing air from the lever’s reservoir

• Attach the oil funnel without the oil stopper to the brake lever’s reservoir by screwing it in clockwise.

• Fill the syringe with the mineral oil.

• Attach the syringe to the caliper bleed point or bleed port and secure it with a strap to prevent it from coming off.

• Gently loosen the bleed screw to allow for fluid flow.

Removing air from the caliper

• Press the syringe plunger to introduce mineral oil into the system. As you do so, the brake fluid will displace air, and you will observe the mineral oil, along with air bubbles, flowing through the funnel.

• Do not press the brake lever during this process, as it may push out the fluid without removing air.
• Continue the process until there are no more air bubbles coming out and only pure brake fluid flows through the funnel.
• If the syringe is nearly empty, close the bleed screw, refill the syringe, and continue.
• Once there are no more bubbles, tighten the bleed screw to seal the system.

• Replace the syringe with an empty oil bag or bottle to collect mineral oil pushed from the funnel.

• Loosen the caliper bleed point, allowing the brake fluid, along with air bubbles, to exit the caliper through the tube.

• Keep an eye on the mineral oil level in the funnel. Top it up if necessary to prevent air from entering the system, which would prolong the bleeding process.

• Once all the bubbles have been expelled, close the bleed screw to seal the caliper.

• Press the brake lever and use a rubber band or strap to secure it to the handlebar.

• Open and close the bleed screw quickly two or three times to remove any remaining bubbles from the brake caliper.
• Cover the area around the caliper bleed point with a paper towel or rag and remove the tubing with the oil bag or bottle.
• Transfer the remaining mineral oil from the funnel or bag/bottle to a separate container for proper disposal or storage.

• Use isopropyl alcohol and a rag or paper towel to clean the caliper, removing any residue of mineral oil.

• Refit the bleed port cap

Removing the remaining bubbles

• Press and release the brake lever repeatedly. There might be additional air bubbles coming out into the funnel. Repeat this process until no more bubbles appear, and the lever feels increasingly responsive.

• If the lever still feels spongy, consider repeating the bleeding process.
• Move the lever up 30 degrees from the horizontal position and repeat the pressing and releasing of the brake lever to ensure no bubbles remain.

• Now move the lever down 30 degrees from the horizontal position and repeat the process until no bubbles appear in the funnel.

• Insert the oil stopper into the funnel.
• Unscrew the funnel anticlockwise to detach it from the brake lever’s reservoir.

• Transfer any remaining mineral oil from the funnel to a container.
• Place the seal onto the upper bleed screw, and securely refit the bleed screw into position.

• Use isopropyl alcohol and a rag or paper towel to thoroughly clean the lever, removing any remaining traces of mineral oil.

• Take out the bleed spacer.

• Install the brake pads back into the caliper.

• Place the pad axle back into position, and if applicable, reattach the caliper spring clip or retaining split pin to secure the pads in place.
• Refit the wheel. If you’re not sure how to do this refer to our article about how to fit the front wheel on a bike.
• Check the performance of the brake lever by squeezing it to activate the brakes. Verify that the lever feels responsive and provides sufficient braking power.
• Inspect the entire brake system, including the caliper, hoses, and connections, for any signs of fluid leakage. Ensure that there are no visible leaks.

Conclusion

Learning how to bleed your Shimano disc brakes is a useful skill. Taking care of your brake system by removing air bubbles and replacing old fluid can greatly improve your bike’s braking performance and keep you safe on the road or trails.

By following our step-by-step guide and taking the time to bleed your Shimano disc brakes properly, you’ll enjoy better performance and have more peace of mind while riding.

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