Sticking piston?

Boudreaux · 03-06-2006, 08:36 PM

I recently changed my brake pads on the front, and it feels as if my braking power has actually gotten WORSE...

I have some brake fluid sitting right here that i'm gonna throw in there in the next coupla days, but the fact that braking got worse concerns me b/c i don't want a sticking piston...what are the odds of a piston being stuck being the cause of my braking woes?

'99 Honda CBR F4 11,4xx miles...

RayOSV · 03-06-2006, 09:38 PM

I think that pistons usually stick on retract not when applying pressure. What kind of pads did you use? Did you bed them in properly?

Boudreaux · 03-06-2006, 11:12 PM

Quote:

Originally Posted by RayOSV

I think that pistons usually stick on retract not when applying pressure. What kind of pads did you use? Did you bed them in properly?

I used Galfer HH sintered pads...

As far as bedding them in, i've been taking it easy for the past few rides (not too long) but there was an instance (just 1) where i had to do an emergency brake...but it wasn't major, i don't beleive...I have been doing my best to use 50/50 front/rear braking as well...its been under ~150 miles since i put them in

and let me be more specific...

Worse: I have to apply more pressure on the brake lever to get the bike to stop, i. e. the front brakes feel more "spongy"...

By "stuck" i mean, stuck in the 'back' position, not fully extending. As a result of pushing them back (in) when i put new pads in...but i havnt visually checked this...

RayOSV · 03-07-2006, 01:19 AM

Bedding in refers to the pad manufacturer's recommendations for heat cycles to condition the pads for maximum braking. Some recommend taking it easy for the first 100 miles or so and some recommend a few increasing pressure hard stops right at first.

It sounds like you may have introduced air into the master cylinder. Did your fluid level rise significantly with the new pads? Did you bleed the brake lines when you were all done? Has the brake fluid ever been completely changed? It should be every 2 years or so.

Check that the pistons push both pads in on both calipers and retract freely.

Boudreaux · 03-07-2006, 09:33 AM

Quote:

Originally Posted by RayOSV

Bedding in refers to the pad manufacturer's recommendations for heat cycles to condition the pads for maximum braking. Some recommend taking it easy for the first 100 miles or so and some recommend a few increasing pressure hard stops right at first.

It sounds like you may have introduced air into the master cylinder. Did your fluid level rise significantly with the new pads? Did you bleed the brake lines when you were all done? Has the brake fluid ever been completely changed? It should be every 2 years or so.

Check that the pistons push both pads in on both calipers and retract freely.

I don't know if the fluid level significantly increased...no, i didnt bleed the brake lines when i did my pads. DUnno if the fluid has ever been changed, but i know it needs to be done.

I just figured, even if the fluid was old, i would still see *some* benefit to new pads..i'm bleeding the brakes and putting new fluid in this weekend

Boudreaux · 03-09-2006, 06:26 PM

Alrighty, changed the brake fluid today....totally, new fluid and everything..my next question

Is it possible i have "glazed" over my pads when i had the emergency stop? My buddies dad who was with us when we did the fluid said that "glazing" them over is bad, will it be obvious if i have? or what should i be looking for...

and if they ARE glazed over, are the pads worthless or will it just take longer to get them bedded in?

Süsser Tod · 03-09-2006, 07:13 PM

Glazing will make them noisy, but braking will be there.

Are you still having a spongy brake lever?

Have you noticed if the pad is already making full contact with the rotor? Maybe you took it to light with them and they arent fully "broken in".

For the new pads on my bike, I just installed them and went for a ride, about 150 miles, rode as I normally do, and they did fine at the track.

Boudreaux · 03-10-2006, 12:03 AM

Alrighty, just got back from a really good ride, brakes are working really good...but i've noticed that the resevoir is seeping out brake fluid a little bit. Is this normal? anything to be concerned about? It's not "a lot" but its seeping.

Its seeping from where the cap meets the body...I've got it screwed down pretty good...?

And is it possible I'm going to need to re-bleed the brakes b/c i've introduced new air into the system?

Boudreaux · 03-10-2006, 05:08 PM

I checked it out more closely today...

First, I pumped the brakes a few times after wiping down the cap/reservoir seal...seemed like there was fresh fluid, although it did seem to be the "old" fluid.

So, i tightened down the cap better (which i think was the main problem) and took it for a spin...minimul leaking still occurred, but not nearly as much as before.

Here is what i think went down. When i changed the fluid, i didn't wipe off the part called teh "diaphragm" and i think that putting it back on squeezed out some of the old fluid and also didnt make a really good seal...

I tightened it, like i said, and im going to keep a close eye on it to see if it keeps occuring, brakes feel pretty good.

RayOSV · 03-10-2006, 05:20 PM

There should be NO brake fluid leaking from the master cylinder reservoir or anywhere else for that matter. Keep in mind that brake fluid is caustic and makes a great paint (and skin) remover.

Either the master cylinder is over-filled or the diaphragm isn't fitting right, but it shouldn't leak. There should be a little window to check the fluid level in which you should see at least a small bubble at the top.

Boudreaux · 03-10-2006, 08:17 PM

Quote:

Originally Posted by RayOSV

There should be NO brake fluid leaking from the master cylinder reservoir or anywhere else for that matter. Keep in mind that brake fluid is caustic and makes a great paint (and skin) remover.

Either the master cylinder is over-filled or the diaphragm isn't fitting right, but it shouldn't leak. There should be a little window to check the fluid level in which you should see at least a small bubble at the top.

I see the bubble, and i don't think its unreasonable that the diaphragm isn't fitting right b/c of the old stuff still being on it, b/c i didn't wipe it off...