Freaking weird brake problem...

[Jobberwocky]

I've been fighting my front brakes since I got my project.

The problem: extremely spongy lever. I can use 1-finger it pull the lever to the bar...

The details: I think the problem is somehow in my left caliper. When I squeeze the brake lever the caliper makes a sqeaking-type sound and the bottom of the caliper moves away from the rotor. Not very far, but it makes the caliper do a wiggling motion. The right caliper does neither.

In order to see if the pistons were actually moving I took the caliper off the rotor and applied brakes until the pistons were pushing the two pads together. Oddly enough, this significantly improved my brake lever's feel but it still isn't what it should be.

Whats even more weird is when I moved the pistons back into the caliper (w/o opening any possibility for air to enter) and put them back on the rotor, my lever was back to its terrible spongyness as before.

What I've done to try to fix it: Nearly everything. I've looked up every thread even remotely related to this issue on this forum.
I've:
-Rebuilt master cylinder
-Rebuilt both calipers
-Installed G&J steel braided 2-line setup
-Bled the brakes for hours
-Done the magical lever tying trick for days
-Have not replaced pads due to lots of life left
-Have not replaced rotors due to lots of life left

I'm so freaking annoyed, any help would be greatly appreciated!

[yngveny]

Sounds like you still have air in the system somewhere.
Try cracking the bolt at the MC as you apply the brake, to make sure there is no air trapped (take care not to spill brake fluid to any painted parts)

Otherwise I would suspect air to be trapped in calipers somewhere.

[mammut89]

can I recomend using a one way stop valve when you bleed it. maybe you are already ?

[GytRDunKat]

I concur, sounds like air. Do a search for bleeding brakes, it's been hashed, rehashed, and over hashed many times on here.

[Wild-Bill]

Stupid question time... When you've bled the brakes, did you bleed from BOTH the bleeder valves on BOTH calipers? (Emphasis on 'both' since I've never had a bike before that had two bleeders on each front caliper. Took me by surprise the first time.)

[Jobberwocky]

Ok, thanks guys, but:
-I have cracked the MC, didn't help
-I don't have speed bleeders
-As mentioned in my post I have already searched EVERY thread dealing w this issue.
-I have bled both calipers multiple ways to no avail. (vacuum pump, syringe, traditional way)

Anyone have the problem w the caliper 'wiggling' when brakes are applied?

[methodicreign]

could the caliper bolts be too long and not holding them in place. I had a similar issue with a car a little while back. try shimming them and see what happens

[belgum]

Your disk is warped. Every rotation of the wheel is pushing the pads further back than they return with one squeeze of the lever. Doesn't have to be much out of true to exhibit this problem. Had it with a motocross bike years ago, drove me nuts trying to bleed it before i found the warped disk.

[yngveny]

I believe belgum have a point, would definitely check the disks for warping.

However that should make the lever firm when pumping it while standing still right?
So most likely there is also air in the system somewhere.

[Jobberwocky]

Thanks for the ideas. I don't think it's a rotor being warped because this happens when I'm not moving. When its up on the center stand and I'm bleeding or applying the brakes this happens.

I have to agree that there is air in the system bc of the spongyness but I'm still not sure why the caliper sqeaks and wiggles when I pull the lever.

But why did the lever feel firmer when I took the caliper off and then was horribly spongy when I put it back on?? I don't get it....

[letsride]

Spongy is air in the line. Start first with the butt of a screw driver and gently tap the calipers, line and master cylinder. This will dislodge any air bubble. Then go to the left caliper and open the bleeder all the way and wait till fluid starts to come out then shut, go to the right and do the same thing. After that start back at the left pump the the master about 3 or 4 pumps hold down the lever and open the bleeder a second then close do it. Do it till no air comes out then go to the right and do the same. If there in no air getting in front the system it will bleed out. If you take your time and do it this way it will go easy. When you hold in the lever dont let it go till you lock the bleeder

[Jobberwocky]

Thanks. I've been doing it exactly that way the whole time.

Spent another hour bleeding last night to no avail... I finally got my vacuum bleeder to work properly. As Tmod suggested to me, I teflon taped the threads of the bleeders. Before this, my vacuum bleeder would just suck air through the threads.

I went through probably about 4 or 5 reservoirs worth of fluid with the vacuum bleeder but it didn't help one bit...

[mammut89]

ok lets just assume that there is no air since youve spent that much time on bleeding in 9 gazillion ways.

next in line that comes to mind is this:

on way or another your pads are not touching the disks hard enough.


1. your pads are misplaced and therefore in someway only a small part of it is touching the disk. if there is a kink to the brake pad and its not touching it flush you might get this. I dont know how im supposed to explain this ive got a stupid picture to help:



You might have the same type of problem with your cylinders pressing against walls and getting stuck halfway in.

[letsride]

Lets start from the begining. What did you to. Change lines and so on. Sorry My time is so limited I have not had time to read the whole thread.

[PepeBouchard]

I think Mammut is on to something. When you remove caliper the pads can apparently move enough to fully seat against each other (no sponginess), but not while installed with rotor. I would really look at thye caliper that is 'moving'. You caliper should NOT be moving. Good luck, I really want to hear the final solution.