How to Bleed Brakes


As part of our Brake workshop we covered the basics on how to change your brake fluid. This is simple and effective maintenance to keep your bike running smoothly and safely. 

You should change your brake fluid once a season. 

Parts of the wheel and calliper brakes

How it all works

With hydraulic brakes, the brake fluid is held in the master cylinder (that cup on your bars), and fills the brake line down to the callipers. The fluid fills down behind the piston in the calliper, and when the lever is depressed, it pushes the piston forward, depressing the brake pads and putting pressure on the rotor. Good brake lines don't expand, fluid doesn't compress, it's basically the law of displacement. 

A well-maintained brake line, free of cracks, and with fresh brake fluid is a key to a responsive and reliable brake.

How Often

Your brake fluid should be flushed once a year.

It is best to change your brake fluid around the end of the season. Due to the nature of brake fluid, which will absorb water from the atmosphere, it’s important to use fresh or new brake fluid, and to keep the cap on the bottle as much as possible.

As the fluid will still absorb some humidity, it’s a great idea to change your fluid before winter storage, to ensure that fresh fluid is sitting in your lines while the bikes is in storage. This means that the internals of your lines and braking system will be less inclined to corrode over time

Pads and Rotors

Your brake pads should always be in contact with your rotor. You will hear them rubbing a little bit.

The constant contact is meant to prevent small particles from getting stuck between the pad and the rotor and causing damage to both. If you have lines worn into your rotor that is what it would be from. If you are changing your Rotor, you should also change your pads, as the damage on your old pads would translate onto the rotor.

 2 piston Calliper brake

Brake Bleed How To

1) Put your bike on it’s center stand, or support as necessary in order to get the master cylinder level. Take off the top cap, and the rubber sealant and clean with a clean rag.

2) Use a syringe to suck out the fluid from the reservoir. Remove all the used brake fluid, and then wipe the cylinder clean.

DON'T depress the brake lever while the cylinder is empty.

3) Fill the cylinder with fresh, newly opened brake fluid (not the same stuff from last year) to the level indicated. BE SURE to use the correct brake fluid as listed on the cap of the master cylinder. Different Dot fluids have different mineral make-up and shouldn’t be interchanged.

4) Put the brake bleeding tube and the appropriate wrench onto the bleed port and put the end of the line into a waste cup (anything will work fine).

5) (The big one) Depress the brake lever

Open the brake bleeding port

You should see some fluid come down the tube.

Close the bleed port

DON'T let air go up the line, into the port. Always close the port before releasing the lever or it will suck air up into the line. 

Release the brake lever

 6) Repeat step 5 until the brake fluid turns colour (becomes clear) then you know you have cleared all the old fluid out of the lines. Close off the bleed port and put the rubber cap back on it.

Check that the level in the master cylinder is still accurate, and close it.

If the cylinder is over filled, it may start to apply the brakes when the brakes are hot, as the fluid will expand when it is hot.

Master cylinder looking good

Hot Tips

-DON'T spill brake fluid onto your paint on your bike. IF you do get some on the paint, don’t rub it in, but simply rinse it away as much as possible with fresh water. The water will dilute the Brake fluid and decrease the damage.

-Your brake fluid should be changed once a season. You should regularly check your fluid if you see noticeable difference in the level of fluid in the cylinder.If you see your braking power go down. you may have a leak in the system or you've boiled your brake fluid through hard use.

-Check your rotor regularly for wear such as discolouration, lots of dust from the brake pads, grooves or cracks. Small nicks and chips may just be from debris on the road, and shouldn’t be a concern, just be aware if they spread into a larger crack.

 


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