Brake Pad Squeal while driving

[Guest]

I have a 1977 GS 750 with the front brakes swapped for the 1981 GS dual disc set up.

I recently took my front brake pads off and cleaned them, and after replacing them they squeal while driving.

The squealing stops while I apply the brakes.

Is this cause by the brakes being engaged all the time? (The pads touching the rotors nonstop)

How can I fix whatever is cause this?

Thanks!

[jbthomp]

What did you use to clean them? You should never need to clean brake pads. If they ever get contaminated with oil or brake fluid they will need to be replaced.

[dorkburger]

I just had a similar problem. My rear brake was dragging slightly, so I changed the rear brake fluid and checked the master cylinder for the first time......ever (bad on me). After the pedal travelled more then it had in years, the piston in the master cylinder became stuck and wouldn't pump. I wonder if yours may be holding a bit of pressure on the brakes.

[gettingtobeaguru]

I used brake cleaner to clean them, and followed the instructions on http://members.dslextreme.com/users/...eplacement.pdf.

The left caliper was missing the pad spring, and the pad guides.

The pad shims from both calipers had severe corrosion (maybe rust, or remnants of the grease used by PO).

Also I don't need pad shims on both pads do I? They only go on the side touching the piston correct?


Dorkburger - How did you manage to fix that?

[gettingtobeaguru]

This is the diagram I'm working from when I give part names. It matches up exactly with the brakes on mine.

[gettingtobeaguru]

I've got an order for the proper shims in now. I'll update after installation.

[gettingtobeaguru]

Ok so update. I unbolted the calipers again to add the new shims and all and tried rolling the bike around. It rolls 20 times easier.

This leads to me to look at the pistons and it seems to me that the piston for the left caliper is stuck out.

I'm not sure what the next step should be. Should I pull the piston out and clean, and grease it? If so how do I go about doing that?

[DanTheMan]

Ok so update. I unbolted the calipers again to add the new shims and all and tried rolling the bike around. It rolls 20 times easier.

This leads to me to look at the pistons and it seems to me that the piston for the left caliper is stuck out.

I'm not sure what the next step should be. Should I pull the piston out and clean, and grease it? If so how do I go about doing that?

Don't ever get any grease in you hydraulic brake system! Your caliper needs to be taken apart, completely cleaned, new o-ring installed, new boot, and all passages cleaned out. Then the brake system has to be bled to remove intrapped air.

[gettingtobeaguru]

Thanks Dan, I realize now that's not exactly what you're supposed to do. I popped out the pistons and cleaned, and flushed them thoroughly. I also bought a mighty vac (well a knock off one) that I'm going to use to try and get all the old brake fluid out when I finally get around to bleeding them.

I do have some Ultra Disc Brake Caliper Lube that says it can go on the boots and the O-rings. What are your thoughts about that? I just worry about them drying out prematurely.


Also:
Could I paint the inside of the pistons? I'd tape off the outside completely.

One of them is pretty rusty inside (not the outside at all thankfully), and I wonder if after cleaning some paint would help prevent that from happening again. I'd be using hi-temp header paint, and I'd bake it properly before installing.

Just to clarify no paint would ever touch the outside of the piston. I would loop the tape over the edges so only the inside of the cylinder was being painted.

Thoughts?

[Grimly]

What did you use to clean them? You should never need to clean brake pads. If they ever get contaminated with oil or brake fluid they will need to be replaced.

They get covered in road clag and dust, so cleaning them and the calipers/brackets/sliders is a good thing and comes under the heading of normal maintenance.
I agree with the oil/fluid comment, though. They're fairly resistant to breakdown, but trying to regain function after contamination is usually fruitless.

[gettingtobeaguru]

Just to clarify, I'm not cleaning the brake pads.

I've got the calipers apart, and I'm cleaning them and the pistons. The brake pads are so far untouched.

[GateKeeper]

here is what your calipers can look like,,,and yes I painted the inside of the piston as well

http://www.thegsresources.com/_forum/showpost.php?p=1585272&postcount=590

http://www.thegsresources.com/_forum/showpost.php?p=1619660&postcount=818

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