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Hyd Brakes- pistons mostly closed, how to open back up?

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Hyd Brakes- pistons mostly closed, how to open back up?

Old 04-02-20, 06:21 PM
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Toadmeister
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Hyd Brakes- pistons mostly closed, how to open back up?

Tektro Draco Hydraulic disk Brakes.

​​​​​​Doing my first ever Hyd brake maintenance, took pads and spring out to clean them off. Put back in. Now I see the pistons are partially closed and I can't fit the wheels rotor back in between them.

I must have done something wrong? See pic



I may have loosened the bolt/cap near the break handle reivoir, would that have depressurized the brakes? Do I need to bleed the brakes now?
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Old 04-02-20, 06:56 PM
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That will happen if you happen to squeeze the brake lever when the disk/wheel is not in place. As the disc space is now quite tight you will need to remove the pads and press the pistons back in with something smooth that will not scratch the piston. First, clean the piston sides since you have access. I like to use q-tips and isopropyl alchohol. I would clean the disc too since you have the Isopropyl alchohol in your hand. Then apply pressure to push the pistons back into the housing. Make sure to press evenly so the piston does not bind. Then replace your brake pads and install the wheel with disc. If you know pump the brake lever until it is firm and the pads are pressing out to the disc.
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Old 04-02-20, 07:02 PM
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Thanks! That makes sense as I probably did squeeze the break lever. I’ll report back.

i actually did clean those break pads with alcohol, that’s why I took them out to begin with

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Old 04-02-20, 09:20 PM
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Originally Posted by bikeaddiction1 View Post
That will happen if you happen to squeeze the brake lever when the disk/wheel is not in place. As the disc space is now quite tight you will need to remove the pads and press the pistons back in with something smooth that will not scratch the piston. First, clean the piston sides since you have access. I like to use q-tips and isopropyl alchohol. I would clean the disc too since you have the Isopropyl alchohol in your hand. Then apply pressure to push the pistons back into the housing. Make sure to press evenly so the piston does not bind. Then replace your brake pads and install the wheel with disc. If you know pump the brake lever until it is firm and the pads are pressing out to the disc.
turned out all good, thanks!
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Old 04-03-20, 03:15 AM
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Also for what it's worth you really don't need to/shouldn't be cleaning the pads. If they're not contaminated manufacturers suggest letting them run--if they're contaminated, they're pretty porous and are very difficult to get clean again and should just be replaced. Hydraulic disc maintenance includes replacing pads when worn, truing rotors and replacing them when they are less than 1.5mm thick (for most brands), bleeding brakes regularly, cleaning, lubricating, and exercising pistons, etc.

And yeah, pads advance automatically so don't squeeze the lever without a rotor or spacer in there. You can spread them with the pads in using https://www.parktool.com/product/hyd...n-press-pp-1-2 or very carefully using a flathead screwdriver.
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