How to Bleed Motorcycle Brakes

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How to Bleed Motorcycle Brakes

As motorcycles have become larger, faster, and more widely used, the need for an improved braking system has become more important amongst riders for their safety needs. This means that motorcycles have moved away from mechanical drum brakes to use the more complex disc brakes. These disc brakes come as standard on the front of nearly all modern motorcycles, and require bleeding periodically.

Bleeding the brakes is a routine part of motorcycle maintenance. It ensures that the brakes are in full working order. During the bleeding process, trapped air is removed from the brake line, reducing the probability of brake failure. The bleeding process may need to be completed on just the front, or both the front and back brakes depending on whether the motorcycle has rear disc brakes. Brake fluid is a necessary component for bleeding the motorcycle parts. It can be bought from garages and some DIY shops, as well as retailers such as eBay. Before bleeding the brakes, drivers should familiarise themselves with the various types of brake fluid and understand when to change it.

Why Motorcycle Brakes Need to be Bled

Modern motorcycles use hydraulic brake and clutch systems in order to provide maximum stopping power and to counteract the use of stiffer clutch springs in high powered engines. However, during normal use, the brake fluid used by these systems tends to absorb condensation in the form of water. This addition of water to the brake fluid reduces the hydraulic pressure needed to operate the brake callipers and clutch cylinder. This means that periodic bleeding, or draining, of the brake fluid is required to remove condensation.

Types of Brake Fluid

Although all brake fluids accomplish the same task, they come in two distinct types: mineral and silicone based. Mineral based brake fluids include DOT 3 and DOT 4, while DOT 5 is categorised as silicone based. Choosing the best type often depends on the motorcycle manufacturer's recommendation, as well as what type of climate the vehicle is driven in.

Type of Brake Fluid

Description

DOT 3

Mineral based

Conventional brake fluid

Dry minimum boiling point of 205 degrees Celsius

Wet minimum boiling point of 140 degrees Celsius

Can be safely mixed with DOT 4 and DOT 5.1

DOT 4

Mineral based

Generally not used in motorcycles due to their aggressive braking

Dry minimum boiling point of 230 degrees Celsius

Wet minimum boiling point of 155 degrees Celsius

Can be mixed safely with DOT 3 and DOT 5.1

Does not absorb moisture as quickly as DOT 3

DOT 5

Silicone based

Used in antique or collectors' motorcycles that are not driven for long periods of time

Not suitable for ABS systems

Dry minimum boiling point of 260 degrees Celsius

Wet minimum boiling point of 180 degrees Celsius

Cannot be mixed with any other type of brake fluid

Does not absorb water, but it does absorb air, which makes the pedal feel soft or spongy

Purple

Does not harm a motorcycle's paint

DOT 5.1

Higher boiling point than DOT 3 and DOT 4

Popular in racing vehicles

Dry minimum boiling point of 260 degrees Celsius

Wet minimum boiling point of 180 degrees Celsius

Can be mixed safely with DOT 3 and DOT 4

Absorbs moisture, which reduces the boiling point

Buyers should take special precautions when working with DOT 3, DOT 4, and DOT 5.1 brake fluids as they can damage the motorcycle's paint if there is contact. In addition, the fluid is highly flammable and poisonous.

Bleeding the Front Brakes

Brake fluid should be changed once a year in humid conditions or every 18 months in dryer conditions. As the brake fluid absorbs water, its composition changes and decreases the motorcycle's braking power. Each time the brake fluid is replaced, buyers need to bleed the air out of the braking system.

Preparation

In order to bleed the motorcycle front brakes properly, riders should start by opening the brake master cylinder reservoir. Depending on the type of motorcycle, this process can vary slightly, so it is best to consult the owner's manual. The most common way is to pull the cover off the master cylinder by removing the screws on the rectangular cover on the top. This is best accomplished with a Phillips screwdriver. If there is no cover, riders can just unscrew the cap from the reservoir.

Fill the Master Cylinder

Next, fill the master cylinder reservoir with the proper brake fluid designed for the motorcycle; most frequently DOT 3. It is important to keep the master cylinder from running out of fluid throughout the entire bleeding process.

Turn the Bleeder Valve

Locate the bleeder valve on the brake master cylinder and remove the rubber cap. Then press a quarter-inch diameter clear vinyl hose at the end of the bleeder valve. The other end of the hose should be placed into a clean, clear container. The container should then be filled with the proper brake fluid until the fluid submerges the end of the hose. Next, pull and release the front brake lever repeatedly until the lever becomes firm. Holding the lever inward, then turn the bleeder valve about a quarter-turn with a combination spanner to open it.

Let the Fluid Flow Out

At this point, the fluid should flow through the hose. If bubbles are present, this indicates that more bleeding is required. In this case, buyers should tighten the bleeder valve by turning it before releasing the brake lever and repeating the process until few or no bubbles appear in the fluid flowing through the hose. Once done, remove the hose from the bleeder valve, pinching it to prevent fluid from flowing out. It is important to note that not every motorcycle has a bleeder valve on the master cylinder, in which case this step can be skipped.

Bleed the Front Calliper

Next, look at the top of the brake calliper to find its bleeder valve and remove the rubber cap. Using the hose, repeat the process above to bleed the front calliper. Once complete, it is important to test the brakes by pulling the front brake lever. If it does not feel firm, the entire process should be repeated.

Bleeding the Rear Brakes

Riders should begin bleeding the rear brakes by finding the rear brake master cylinder reservoir and removing the cap. Next, brake fluid should be added to the master cylinder reservoir until it reaches the "max" line. It is important to prevent the master cylinder reservoir from running out of fluid during this process. If this happens, it negates all of the bleeding performed.

Turn the Bleeder Valve

Find and remove the cap of the bleeder valve on the rear calliper. In a similar way to bleeding the front brakes, one end of a quarter-inch diameter of clear vinyl hose should be connected to the end of the bleeder valve, while the other end is placed in a clean, clear container. Add brake fluid to the container until the fluid submerges the clear hose. Press and release the rear brake pedal until it feels firm, typically 5 to 10 strokes, then hold downward pressure on the pedal, while opening the bleeder valve and watching for bubbles.

Close the Bleeder Valve

The bleeder valve should then be closed and the rear brake pedal released. The process should be repeated until no bubbles can be seen flowing through the hose. It is important to note that the rear brakes do not need bleeding if the motorcycle does not have rear disc brakes.

Buying Motorcycle Brake Fluid on eBay

Riders that would like to purchase brake fluid for their motorcycle on eBay can start by going to the eBay home page. From there, you can enter any related key terms into the search bar such as "brake fluid". For a more precise search, try entering more specific key terms such as "DOT 3 brake fluid". Once on a search results page, you can continue to follow the subcategories to further narrow down your choices. For those that wish to browse listings within a certain price range, eBay offers an advanced search feature to help buyers to select a budget limit. This can help you to determine which sellers are offering the best deals on the brake fluid that you are interested in buying.

Know the Seller

Before purchasing brake fluid, you should get to know the seller. Buyers are free to contact the seller for additional information about the product. This is best done by using the "Ask a question" link. Buyers can check to see if other customers have left positive feedback on the seller's profile. Positive feedback indicates that sellers have proved that they offer excellent customer service and good quality products. You can also look for listings from Top-rated sellers. These sellers are known by the eBay community for providing the highest levels of reliability.

Conclusion

Bleeding the brakes is a regular part of motorcycle maintenance. While it is possible to have this process completed by a professional mechanic, riders may choose to bleed the brakes at home. Doing this is often the more cost effective option, saving both time and money. Before bleeding the brakes, riders should make sure that they are equipped with the proper tools and brake fluid required to complete the task at hand successfully. There are several brake fluid DOT ratings; choosing the right one is important for the proper functioning of the motorcycle. While DOT 3 brake fluid is the most commonly used for motorcycle maintenance, buyers should always consult the owner's manual before choosing a type.

If the motorcycle has rear disc brakes, buyers must bleed both the front and rear brakes. Doing this can improve brake performance dramatically and prevent complete brake failure, which may occur as a result of large amounts of air entering the brake line. eBay has a wide variety of brake fluid, designed to fit the needs and budget of every motorcycle owner.

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