Question: Matt wants to know: Do you have any tips on how to bleed brakes without a bleed kit?
Answer: While there is no true substitute for a good bleed with the manufacturer’s bleed kit, I do have some tips that can help you out if you find yourself in a situation where you don’t have access to a bleed kit. These tips will work equally well on road hydraulic brakes and mountain bike brakes.
Most brake bleeds are done because a brake line was shortened during an installation. Cutting a brake line introduces air into what is usually a good factory bleed. If you are careful when reinstalling your brake line into your lever, you can get nearly all of the air out.
After cutting the hose and installing your hose barbs and olive, lay your bike on its side with the brake lever you are working on closest to the ground. Place a drop or two of your brake’s hydraulic fluid into the open end of the hose and into the open end of the lever. Bring the hose and lever together in such a way that you avoid having any of the hydraulic fluid spill out before the surface tension of the fluid in both components has a chance to adhere to each other. Then press the hose into the lever and let the excess hydraulic fluid spill onto a rag that you have ready to catch it.
Thread the assembly together following the manufacturer’s instructions and then check your bleed. Pump the lever a few times to work any air that might have made it into the line up to the top of the lever. If you have any air in your brake’s hydraulics, you want it to be in the master cylinder reservoir where it will typically stay.
You can check to see if air in your master cylinder reservoir will be a problem by bouncing the front wheel up and down then pulling the brake lever to see if it feels mushy. Bouncing the levers up and down will froth the fluid if there is any air in it and will usually work any air into the piston assembly or the brake line where it will affect your brake’s performance.
If your brake lever feels soft after doing the bounce test, you’ll need to add another step to the process. Pump the lever until all the air works its way up to the top of the master cylinder reservoir. To make sure that the air made it there, pull the lever tight and then hold it. If the lever gets soft after the pads initially contact the rotor while you are holding down the lever, not all of the air has made it up to the top of the lever.
Pumping the lever as well as pulling it tight and letting it go will help to work bubbles up to the top of the system. Placing the bike in the stand so that the caliper is much lower than the lever can help. Once the brake feels solid, set your brake lever so that the bleed port is pointing up and then remove the bleed port screw or the master cylinder cover if your brake has one. Then top off the fluid and reinstall the bleed port plug or master cylinder cover.
Repeat the bounce test to check your work. If your brakes are still inconsistent, you’ll need to do a proper bleed to get the air out.
You may have noticed that this method is a bit of a hassle, because as I said before, there is no true substitute for a proper bleed. So do yourself a favor and do the job right the first time with the manufacturer’s bleed kit.
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