Lube the brake pistons and pins? HELP!

Mad German · Oct 20, 2005

I recently bled the brakes and cleaned the calipers and pistons really good. However, now it seems like the brakes are dragging a bit. I'm wondering if I should A) have put some sort of lube on the pins that hold the pads in the calipers and B) applied a light coating of new brake fluid to the pistons while I had most of them exposed.

I put a small piece of wood between the pistons and pressed the brake lever a bit to get them to move out of their regular position. I didn't remove them completely, just exposed more of them than is normally exposed when the pads are installed and the caliper is mounted on the fork. Some of the pistons didn't pop out 'evenly', as if they were hanging up a little. Eventually they all popped against the piece of wood, but they didn't do so 'all at once' like I thought they would have.

When I replaced the pads, I just pushed the pistons back into the caliper (without lubing them with anything-like a light coating of fresh brake fluid perhaps?) and mounted the pads and called it a day.

Should I have greased the retaining pin and put a light coating of fresh brake fluid on the pistons before I pushed them back into the caliper? What do you guys do?

I'm thinking that they might not be retracting like they should since they don't have any lubricant on them. Make sense? Any tips or info you can pass along?

Thanks,
Scott

SportbikerR1 · Oct 21, 2005

You didn't happen to pull one of the rings out and pinch it slightly while putting it in did you? When I did my old ninja I did lube the rings slightly with brake fluid, even though the service manual never says to do that. Maybe someone on here will say wether its wrong or not.

JoeC · Oct 21, 2005

Hey Scott,

A few things to mention here. Regarding the pins, they do seem to get goobered up, but don't put any lube on them. Any time you do a pad service or have things apart, take a scotch brite pad and scrub those things until they're nice and shiney. Then put the pads back in and they'll slide on the pins a lot better.

About your pads retracting and pistons, what you did sounds fine to me. Either nothing or a little brake fluid on the pistons and absolutely nothing else. Whenever you move the pistons in and out to clean them, I think what happens is you change the orientation of the two seals on the pistons. There's a dust seal, and seal that actually holds the fluid where it's supposed to be. First you 're pumping the pistons out to clean them, then push them back in to put things back together, then pump the lever to bring pistons and pads bake into contact with the disk.

What this does is leave the seals kinda flexed outwards a bit. And the seals are designed to retract the piston slightly. So what happens is the braked feel tighter initially - and retract the pistons a bit less - then after you ride a while and use the brakes, the seals settle in to where there supposed to be and the lever travel increases a bit, and the seals retract the pistons a bit more.

This is how my brakes behave after I bleed and clean stuff up, and my explaination about what's going on. I could be wrong, but it seems to make sense.

Hope that helps,

-Joe

JoeC · Oct 21, 2005

One more thing, when I pump the pistons out to clean them - as you mention in your original post, they never come out at the same rate. Some pump out easy; others just seem to hang. And they behave the same even after they're all cleaned up. No big deal, just a little more friction on some of them. This is normal and does not affect how the brakes work once they're all pushing on pad and rotor like they're supposed to.

Lube the brake pistons and pins? HELP!

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