[Jbone]

The Front brakes have been making a slight rubbing sound lately and I finally had a chance to have a look. The outside pad on the left Calliper is in there pretty tight and is wedged up against the disc, but comes out no problem. But Pads are looking fine and are well within tolerances. The other pad is loser, but still sits in there ok.

However, on the right Calliper the Inside pad is really jammed in there. Had to really work to get it out as it was pushed right up against the disc... hence the rubbing sound when ridding.

Question: How to fix this? Im thinking a good bleeding might be in order. Did a quick purge of the main reservoir to see if there were any air bubbles on the Master Cylinder side, and no bubbles. HAve yet to do a complete bleed.

Anyone have this issue before?

THanks,
J

 

[Shazaam]

Sounds like a piston retraction problem. You need to make sure that all the pistons are retracting when the lever is released. Block the other pistons movement to isolate each one at a time. Replacing the piston seals will likely fix it.

 

[Jbone]

Hmm... sounds like I'll be busy tomorrow. BTW, I also noticed that the back of one of the pads was covered with what looked like lubricant or something, I can't think of why someone would put something like that on the back of the brake pad. Could it be a fluid leak? If the piston seal on that pad was on its way out, would it let some brake fluid out onto the Pad?

 

[DT996]

When Shazaam is right, he's right. Seals will allow fluid buildup which collects with dirt/dust/grime leaving a greasy buildup just like you see.

 

[Shazaam]

Another possibility is that some brake grease or anti-squeal material has been placed on the back of the pad metal backing plate to damp out any metal-to-metal vibration (brake squeal.).

 

[Jbone]

Bled the brakes today and pulled the pads again and had a good look. Left calliper had some bubbles in the line, but not many. But the right one... the one with the inside pad up against the rotor was fine.

As for the pistons, the inside ones are not out as much as the outside pistons. But from how the calliper sits over the rotor this seems like it is how it should be. Kind of hard to describe.... I'll try taking a picture tomorrow and post it up. Further after having another look, I do think that it is brake grease or anti-squeal stuff that on the pads, as my fluid levels are fine and the stuff isn't the same viscosity as brake fluid... Thanks for that bit of wisdom BTW

But in regards to checking to see which pistons are retracting... is there a thread or link somewhere on this site that I can check out to show me the steps? I can kind of guess at how one would go about it, but I'd like to be sure so I don't screw anything up..... this things my daily commuter at the moment

 

[safetyfish]

Brake cleaner and a toothbrush. Spray and scrub the pistons (dont disassemble the calliper just yet, remove the calliper off from the rotor, take the pads out then start cleaning)

Its a messy job and wear gloves. Hopefully thats all you will need to free up the movement of the piston. If that doesnt work, then you could be up for a seal rebuild which is pretty straight forward but you have to be sure of what you are doing.

 

[Jbone]

Thanks for that. I'll give it a shot when I get home from the gym tonight. I'm hopefull that its just a bit of grime jamming it up as the previous owner was pretty good about keeping his bikes in good working order.

 

[Jbone]

Well, I did as Safetyfish said and unbolted the callipers, gave em a good scrub with brake cleaner and an old tooth brush and a shop rag. After giving both callipers the good news with the cleaner I gave the pistons a good shove back into the calliper with the idea of loosening them and sort of resetting them so they'd sit a little more evenly on the pads.
Wasn't sure if I should do that in case shoving the pistons back into the callipers would effect the brake lines some how. But the brakes feel a lot more grabby and responsive and the rubbing is less than it was.
Anyway, brakes are working well.... but if anyone has any input on that particular method, feel free