Back bleeding your brakes is a quick and simple way to get air out of the brake line. If your brakes ever feel soft or act like there is air in the line, this 30-second trick can make them feel new again. In fading or boiling brakes it will get hot fluid out of the caliper and replace it with cooler fluid from the reservoir.
It is best done with the master cylinder or brake fluid or brake fluid reservoir at the highest point. So with the front brake it is often best to pull the hose and turn the bars to orientate the brake side of the handlebar as high as possible. On the rear brake this isn’t as much of an issue.
Next compress the brake caliper (that is the part that holds the brake pads and squeezes them on the rotor) by holding the wheel and using your knee to push the fluid out of the caliper. Be careful on bikes that have been is use as the caliper is often very hot. Compress it till you feel the piston bottom out. This will have forced most of the fluid back up the brake hose and into the reservoir. Most air trapped in the system will go into the reservoir and float out of the fluid.
Next you must pull the brake lever or compress the rear brake pedal a few times to refill the caliper with fluid and get the system pumped back up. Make sure you take a few seconds between strokes and use full strokes of the lever as not to suck any additional bubbles back into the line. It typically takes 5-8 pulls to fully charge the system. You will feel it get stiff again and often the lever or pedal’s engagement point is now sooner than before.
Do not ride the bike until you verify the brakes are working properly after compressing the caliper and re-pumping them up.
Here is a short video showing you the technique.
One Response to “Tech Tip: How To Back Bleed Your Brakes”
ETicket55 .
Great tip, Jimmy! I would add to your caution about pressing too hard/too far on the caliper as you can force brake fluid past the MC piston seal if you’re … ummm … “too enthusiastic.”