sticking brake piston.

[streido]

Been getting a squeek/rubbing noise from my front end somewhere for a week or so, had a quick look at my pads last week and they looked fine so i assumed it was prob my speedo cable needing replaced. Been getting a little worse last day or 2 so today i disconnected the speedo and pulled out the cable inner then went for a ride to see if it was def my speedo, it wasnt, still had the noise.

That meant it had to be the brakes themselves so i stripped down the front caliper, pads, pins etc and gave it all a good clean and new grease hoping that would fix it. Again that didnt, was ok for almost a mile then it started again. Srtipped it back down and noticed whenipress the brake only one piston goes out, the other is sticking. It does go out if i hold the other one in and press the brake tho. Im guessing both should go out together if its normal?

Think this means one of the pistons is just not as free moving as the other so its either not going out properly or is causing the pad to drag on the disc? Sound right? If it is how do i fix it? Can i just push out the piston and grease it or does it sound like i may need a whole new caliper/piston assembly?

The noise is doing my head in now 

Going to order new pads anyway and restrip it at the weekend if i dont get time before then to try free up the piston if poss. Just wanted to confirm it is a sticky piston tho in case theres more to it than just grease and cleaning it up more.

Cheers.

[blue]

sure sounds like a good sign of bracks going bad. check your wheel bearing to see if they are ok.sometimes just a little greese well fix theam.

[Peters]

Pull the pistons out of the caliper and clean everything really well. An old mechanics trick to getting the pistons back in is to blow compressed air into the brake line fitting to push the rubber seal around the piston.

[MaryK]

As indicated, remove & clean the piston and also remove the seals. 
Be sure to clean the grooves that the seals sit in..... dirt in there make the seals clamp on the piston, thus not allowing the piston to move back away from the disk.
 If the seals are ok, they can be reused, but usually they don't cost much. 
Silicone lubricant or brake fluid can be used as a lubricant when putting the pistons all back together.

Enjoy the 4th safely,

[streido]

Thanks for the info. I'll prob need to wait till fri after work to start it cos i dont want to be left rushing to finish it for my ride to work the next day just in case i get issues. Def think its just needing a good clean up cos the rest of the caliper parts where pretty grubby. Thinking i might even get away with giving it a good soaking in some penetrating oil for a few hours and see how it moves then 1st. If that doesnt free it up then ill have to strip them out. Dont have compressed air tho so might be a little harder to do? Do i need to drain the fluid before i pull out the pistons or is it still sealed inside so the fluid stays in?

Cheers.

[Peters]

You can drain the fluid or not, doesn't matter it'll all come out with the pistons

[Vivo]

It just needs cleaning. corrosion makes it not move freely.

[zombie]

It's best to hone the piston bores. Water will sit in the lowest portions corroding the bore. A Bike pump will get out the pistons but wrap the caliper in rags as they will shoot out, and bring a hell storm of fluid with them

[streido]

Well i rode to work this morning and for the 1st mile or brake was rubbing/dragging as usual. When i was pulling the brakes i made a point of pumping them in and off instead if just giving it one pull and this seemed to help push out the stuck piston better. I had put some copper grease around them last night as far down as i could and pushed them in and out a few times so that may have helped to free things up a bit. After 4-5miles town riding it seemed to go away and didnt come back the rest of the ride to work. Going to order upsome new pads anyway and buy some brake fluid cos stuff i have in my garage has been there for years so is prob out of date now. If it comes back beforevthe weekend i will strip it all down inc the pistons, that'll fix it hopefully.

Thanks everyone.

[blue]

good news is good to here .good luck

[Peters]

Brake fluid is very sensitive to moisture. It does go bad fairly quickly.

[streido]

Brake fluid is very sensitive to moisture. It does go bad fairly quickly.

I got a new bottle tonight so plan on giving the brakes a bleed tomorrow or fri and another clean up and grease. Hopefully that cures it, think it should do.

[Vivo]

Brake fluid is very sensitive to moisture. It does go bad fairly quickly.

Brake fluids are hydroscopic meaning they absorb water from the atmosphere...

that's why you have to change it every year or so..

[streido]

Forgot to update this so better do it just in case anyone has a similair issue.

Turned out it was because of the pins i think, one had a little corrosion on it that i sanded down and it made it better. Took it all alart again and made sure the pin was 100% smooth and clean, regreased it and when i put it back again with new pads in its been fine.

Dont think i even needed new pads but i had some anyway, kept the old ones as spares.

Still fine now over a week later. No noise. 

[zombie]