Rear brake sticking

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Dec 23, 2021 | 02:33 PM

#31

stav

Thread Starter

Intermediate

Joined: Jul 2021

Posts: 31

Likes: 6

From: greece

Thank you all,

Dec 31, 2021 | 02:08 PM

#32

Hey Man

Seasoned HDF Member

Joined: Jun 2015

Posts: 10,284

Likes: 7,766

From: West Central FL

Your pads could be worn down to the point that the brake piston comes out too far or your brake fluid is so old that it has congealed in the caliper. Remove the caliper, pump the brake until the piston pops out and clean out the caliper and reassemble making sure the big "O" ring is replaced in the correct direction. Then clean out the master cylinder, blow out the brake line and flush it with DENATURED alcohol, not Isopropyl alcohol. Put everything back together, fill with DOT5 and bleed the system.

Dec 31, 2021 | 07:31 PM

#33

d24112

Tourer

Joined: Dec 2008

Posts: 271

Likes: 73

From: Stowe Pa

Quote:

Originally Posted by JoeItaly61

I would almost bet its from the piston locking up inside the caliper. It happened to me this summer on my Tour Glide after replacing the brake pads. With the old pads the piston is out farther, when you put in new pads the piston goes in (and takes in some dirt) and starts to work were there is a rough spot on the piston. I pulled the piston from the caliper, cleaned it up (and inside the caliper) hit the piston with some very fine sandpaper (VERY LIGHTLY), and put new seals in. Problem solved!
And naturally CHANGE THE FLUID !!

I agree the piston is locking up from dirt. Here's the quick way to check. Remove the caliper from the bike. Place a wide putty knife or something similar in between the pads. Pump the brake pedal to to extend the pucks and then wash them with brake cleaner. You'll be surprised how dirt comes out. Try this before you go throwing money at it.

Dec 31, 2021 | 08:27 PM

#34

PeterB

Road Master

Joined: Sep 2021

Posts: 759

Likes: 936

From: Under the affluence of incahol.

Quote:

Originally Posted by d24112

^^^^^ Definitely do this. It's common for the piston to develop a ring of corrosion/crud just where it sticks out past the rubber seal. When you put the new thicker pads in, the ring of crud gets pushed back into contact with the seal and causes sticking. Often all you need to do is pump the piston out far enough you can get in there with some Scotchbrite and clean it off then smear a little silicone grease around it to help prevent it happening again. It's a regular part of pad replacement. (or should be.)

It'll help prevent future corrosion if you flush new brake fluid (Dot 5) through the system. Although its not hygroscopic like Dot 4, moisture can creep in around that caliper seal and sit there inside the piston cavity.

The other thing that happens on these older bikes over 20 years old is the hole down the middle of the rubber brake hose closes up and does weird stuff like allow fluid to travel to the caliper, but not back again, which jams the brake on. But as yours is working ok with the old pads, I would suspect the corroded piston as the most common cause.