Blaise Pascal came up with an idea in the 17th century that has since become scientific law. Pascal suggested that when a fluid has pressure applied to it, the pressure is transmitted by the fluid equally in all directions. In the world of motorcycles, this means that your motorcycle is able to efficiently stop using its brakes. These do require some maintenance to keep them working effectively. This guide answers questions like, “Is it safe to bleed your own motorcycle brakes?“
How Do You Bleed Motorcycle Brakes With ABS?
If you’re wondering, “How do you bleed motorcycle brakes with ABS?”, Pascal’s Law is important to know. When you squeeze the brake lever on your bike or press the brake pedal, this causes your master cylinder’s piston to exert force and expel brake fluid. Pressure then expands equally in all directions, moving the caliper piston. This expansion caused by the pressure then pushes the brake pads up against the brake rotors and forces your bike to stop.
The process of “bleeding” your brakes is important to compress and expel air within your brake lines. When air gets in your brake lines, you might press the brake, but the piston will not budge. This is where the term of a “soft” or “squishy” feeling brake comes from. Sometimes your brakes will fail to work whatsoever. Bleeding your brakes is the process of pushing air out of the line and sealing the system.
When a bike already has brake fluid inside it, the process of bleeding the brakes is often straightforward. First, generate pressure by pumping the brake. Then open the bleeder with the brake still engaged in order to expel air. Close the bleeder and disengage the brake. Repeat this process until the brakes no longer feel soft.
What Tools Do I Need to Bleed My Brakes?
In order to bleed your brakes, first ask yourself, “What tools do I need to bleed my brakes?” You will need proper brake fluid along with a brake bleeder wrench. In some instances, a wrench or combination wrench will work for your particular motorcycle. If this is your first time bleeding your brakes, take special care to follow the brake bleeding process to a T. Before beginning the process, always go above and beyond to make sure your bike is completely covered and protected. Brake fluid is known to be especially detrimental to paint and will quickly tarnish a bike’s shiny finish.
Remember to always replace the top on your bike’s master reservoir. While the lid doesn’t have to be tightly screwed on, it should be screwed down at least one or two turns. As you start pumping the system and it begins to build pressure, you run the risk of creating a geyser of brake fluid out the top of the reservoir that can potentially splash onto your bike’s beloved paint.
The bleeding process should always be started at the port farthest from the master cylinder. If your motorcycle manual has specific instructions for the bleeding process, follow those instructions instead. If your bike has dual-disc front brakes, the farthest point is generally the left front caliper. Following this method will drive the most air out in the quickest amount of time, resulting in a quicker job for you. Continue on to the next caliper then to the master cylinder bleed port if your bike has one. This will successfully push out even the harder-to-bleed air from your hydraulic system.
Is It Safe to Bleed Your Own Motorcycle Brakes?
That leads us to the next question – Is it safe to bleed your own motorcycle brakes? The answer is yes, if you follow instructions properly and pay close attention to what you are doing. One quick tip to get your brakes feeling firm is to zip-tie your brake levers down over night. You can also wrap them with a towel to prevent potential damage. Cut the zip-tie or remove the rag the next morning, and your brakes will be ready to go. This process works by applying pressure to the brake lines and driving air into the top of the column. This opens the purge port on your brake line and allows air bubbles to collect and disperse out of the system. If your brake system seems to be especially difficult to bleed, try this fail-safe trick.
In order to bleed your brake system successfully, always use the right brake fluid. Some types of brake fluid are made out of castor oil, while some are made of glycol and other brake fluids are designed with silicone. If any of these types of brake fluids are combined, this can be messy. Only use fluid with the proper boiling point and formulation. DOT 4 can replace DOT 3 fluid, though you should never replace DOT 4 fluid with DOT 3 brake fluid. DOT 5 and DOT 5.1 fluids should never be mixed with one another.
If you are looking to switch out the brake fluid you should do an extended bleed on your system. First, bleed out the vast majority of brake fluid from the line without the line going dry. Then refill the master reservoir and go through the process one or two more times.
If you happen to be unable to achieve pressure within the line, fill up the master reservoir, crack the bleeders, and then watch for fluid to gather at the bleeders. If the caliper on your motorcycle is lower than the master cylinder, gravity will work to your benefit here. Gravity helps to draw fluid through the system and often generates enough pressure to complete the system bleed.
If your bleeder happens to be facing in any direction other than upwards, you will find it difficult to force air to travel against gravity. Air bubbles tend to travel upwards while liquid follows gravity and travels downward. To bleed the system in this scenario, loosen and rotate the caliper until the bleed port is facing upwards. Make sure the pads stay in contact with the rotor; otherwise, you will have to drive the caliper back in.
If you find that your motorcycle has been losing brake fluid frequently, you may have a more serious problem on your hands. Fluid levels are designed to drop as your brake pads wear. If you add too much fluid to your brake system you run the risk of pushing fluid out of the master reservoir when the caliper pistons are driven back into their bores. Brakes are one of the most important aspects of a properly functioning motorcycle. In the event that you do not feel comfortable bleeding your own brake system, always err on the side of caution and take your bike to a professional mechanic to carry out the process for you.
If your master reservoir is not full during the brake bleeding process you will have to start all over again once air gets sucked into the fluid as you attempt to pump the brakes.