How to Bleed Your Mountain Bike Brakes

Although riding a bike can be exciting and adventurous, it’s crucial to check that it’s in good working condition to protect your safety. The braking system is one essential element that must be maintained. The brake lever may become spongy or mushy over time if air enters the brake system. By clearing this air from the brakes, the brakes can once again function as they should. You will learn how to bleed your mountain bike brakes in this tutorial, along with the tools you’ll need, safety precautions, and the procedure for taking the air out of the brake system. You’ll find this manual informative and simple to follow whether you’re a seasoned rider or a novice. So let’s get going!

Step #1 Prepare the Tools You Need

mountain bike brakes

You need to get some tools before you start bleeding your mountain bike brakes. Get all these tools before starting because they are necessary to bleed a brake. Here are some of the tools you need:

  • Syringe or bleed kit
  • Brake fluid
  • Clean towels or rags
  • Pliers or wrench
  • Torx driver or hex key (depending on your bike’s brake system)
  • Bleed block (optional)

Note: In choosing brake fluid, make sure it is the one specified by the bike manufacturer. Also, it must be compatible with the bike’s brake system. And consider its freshness as well.

Step #2 Prepare the Workplace

You need to work in a clean and well-lit workspace. Place all the tools you need in an area that is easy to reach. You also need to set up a container to catch leaks or spills from the brake fluid.

Step #3 Removing Brake Pads

Take the front or back wheel off, depending on which brake you plan to bleed first. For the time being, take the wheel off and set it aside. Remove the bolt holding the brake pads to the caliper using a 3mm Allen key once you have removed the cotter pin.

Make sure to move the brake pads out of the way for the time being to prevent mineral oil contamination. The braking power of the brake pads will decrease if they become dirty.

Step #4 Install a Bleeding Block

If required, force the caliper pistons out with a tire lever. Avoid using a metal screwdriver since you risk damaging or even cracking the ceramic pistons. Use the same bolt that holds the brake pads in to insert the yellow bleed block into the brake caliper. Use a 3mm Allen key to tighten.

Read more: Best Mountain Bikes Under 300

Step #5 Put the Bleeding Cup on the Brake Lever

The brake lever cap screw is located above the lever reservoir. To remove it, use a 2.5mm Allen key. Keep an eye out for the rubber O-ring at the cap screw’s base.

Place the mineral oil in the bleed cup before you screw it into the brake lever. Keep the bleed cup from being cross threaded into the lever. Plastic threads have a high risk of damage if not handled carefully. To guarantee a complete seal, check that the bleed cup base has an O-ring made of rubber. In its absence, air could enter the brake line.

Step #6 Connect the Oil Catcher Bottle to the Brake Caliper

At the bleed port fitting next to the top brake caliper bolt, press the rubber oil line onto the fitting. To ensure that neither air nor oil can escape from the fitting, push the line all the way onto it. While the line is connected to the oil catch bottle, it is perfectly fine for the line to lie inside. Just enough oil is dripping here to fill the catch bottle.

Step #7 Open the Brake System of the Lever And Caliper

To let the mineral oil flow into the reservoir for the brake lever, pull the plug located in the center of the bleed cup.

Open the bleed port at the caliper by turning it an eighth of a turn with the 7mm wrench. Since the brake system’s ends are both open, mineral oil will flow and trickle into the catch bottle. Let the filthy mineral oil fill the catch bottle until fresh mineral oil emerges from the caliper. Below, you can see that the undesirable black oil has already been removed from the system, and fresh oil is now escaping.

Make careful to keep topping off the bleed cup’s mineral oil. The important thing to remember in this situation is to avoid blowing air into the braking system through either open end. If the constant drip flow starts to slow down or stop, you can use the brake lever to force fluid through the line.

Oil has been forced through the line and out of the caliper when the brake lever is pulled and held shut. You don’t want to release the lever because that will result in a vacuum at the caliper. This section is essential.

Release the lever blade, use a 7mm wrench to tighten the bleed port at the caliper, and then reopen the bleed port. If necessary, carry out this procedure several times to keep forcing fluid through the caliper.

Step #8 Close Caliper Bleed Port

Close the brake caliper bleed port with the 7mm open-ended wrench. Keep in mind that some oil may run over the brake caliper as you remove the oil catch bottle and line from the caliper.

Make sure to dispose of the used, dirty oil properly.

Step #9 Install Brake Pads After Cleaning the Brake Caliper

Ensure to keep any mineral oil away from the brake pads. If at all possible, avoid having your hands make touch with the brake pad surface.

Before attaching the brake pads, carefully clean the brake caliper with any degreaser or cleaner.  For the purpose of securing the pads, use a 3mm Allen key. Remember to use the little cotter pin!

Reinstall the wheel in the bicycle and tighten the axle as necessary.

Step #10 Cycle Brake Lever Blade

Your work on the brake caliper should be complete at this point. We’ll finish by performing a lever bleed to eliminate any air bubbles that may still be present in the brake line. When the bleed cup is approximately halfway full, repeatedly pump the brake lever to check for air bubbles rising to the top.

Remove any leftover air bubbles by positioning the breakup and down from parallel after loosening the brake handlebar clamp with the 4mm Allen key. Be careful not to let air through the bleed cup or leak mineral oil.

The intricate design of the brake lever is where air bubbles like to get caught. Open the free stroke screw about two turns from closed using a Philips head screwdriver. To remove any potential air bubbles, reapply pressure to the brake lever. The free-stroke screw should then be fully closed to prevent air from entering the pocket behind the screw.

Step #11 Install the Bleed Lever Cap Screw After Removing the Bleed Cup

Plug the bleed cup and take it from the brake lever once you have eliminated all air bubbles and have a robust lever sensation. Mineral oil should be disposed of properly. Install the bleed lever cap screw to seal the braking system using a 2.5mm Allen key.

Step #12 Clean the Brake Lever and Reposition It

Once more, grab the degreaser or cleaner and wipe any oil spilled on the brake lever. There might still be residual air in the brake system if the brake lever feels squishy. Your bike’s safety is greatly dependent on the braking system working properly. If you don’t have the tools to do the job yourself, bring your brakes to a bike shop to get them serviced by a pro.


The procedure of bleeding the brakes on your mountain bike is easy and requires only a few fundamental tools to complete. You can restore your brakes to their optimal performance if you follow the procedures in this guide. This will allow you to enjoy a ride that is both safer and more assured. Keep in mind that you should always handle brake components with care, use the appropriate type of brake fluid, and work in a clean and well-lit area of the workspace. Happy biking!

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