Screaming! XT 4-pistoners

PB Forum :: Shimano
Screaming! XT 4-pistoners
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flag holytrails
Posted: Aug 31, 2020 at 19:19 Quote
I've got new, brand new XTs on my Tracer. I dont think anything got on them, not even water but dang they scream like a mofo....drives my nuts!

Anyone with this same problem? All my other shimano brakes have been silent
flag eshew
Posted: Aug 31, 2020 at 20:30 Quote
Clean the rotors with rubbing alcohol & a clean cloth. Test them pedaling down the road for a few minutes dragging the brakes. Clean again, drag brakes again. Repeat as necessary.
flag holytrails
Posted: Aug 31, 2020 at 20:46 Quote
eshew wrote:
Clean the rotors with rubbing alcohol & a clean cloth. Test them pedaling down the road for a few minutes dragging the brakes. Clean again, drag brakes again. Repeat as necessary.

I did 1x but ok, its worth repeated tries vs buying new pads.
flag eshew
Posted: Aug 31, 2020 at 23:36 Quote
Hope it worked for you. If not, what rotors are you running?
flag eshew
Posted: Aug 31, 2020 at 23:36 Quote
If you've got metallic pads you can remove them and use a propane torch to heat them up for a good 45-60 seconds. Gently sand after making sure to use a large portion of sand paper to minimize rubbing on the contaminant debris. They do get super hot and that removes all contamination.

I've had to do it 4-5x over the years on various bikes of mine & my friends. Works like a charm & saves the environment & your wallet.
flag holytrails
Posted: Sep 1, 2020 at 1:06 Quote
eshew wrote:
If you've got metallic pads you can remove them and use a propane torch to heat them up for a good 45-60 seconds. Gently sand after making sure to use a large portion of sand paper to minimize rubbing on the contaminant debris. They do get super hot and that removes all contamination.

I've had to do it 4-5x over the years on various bikes of mine & my friends. Works like a charm & saves the environment & your wallet.

Sounds like a good idea. I dont have a torch though but a fire starter/igniter should work.
What grit of sandpaper? 1000+ I'm thinking
flag eshew
Posted: Sep 1, 2020 at 8:31 Quote
The grit shouldn't matter, you'll just be getting rid of the carbon and getting the pads back to their original color.
flag woofer2609
O+
Posted: Nov 5, 2020 at 10:03 Quote
FWIW, on my commuter, I thought I had contaminated pads, or rotors. I did everything; cleaned the crap outta the rotors, burnt, the pads, cleaned the pads, replaced the pads...nothing. I went so far as to switch brakes from another bike which didn't squeal...and? They squealed as well.
For some reason, I don't think the pads are toeing in in correctly, which has more to do with the post or side mounts not being parallel/ perpendicular to the rotor, not the brakes themselves.
You can face the mounts, maybe get a shop to do it.
Just something to think about.
FWIW, this never used to be a problem on this bike, it literally started out of the blue.
Frustrating as all get out!
flag shearflow
O+
Posted: Nov 17, 2020 at 15:21 Quote
Check to see if you have a leaky piston that's leaking mineral oil onto your caliper!

I had this problem on a brand new bike (custom built by myself) and it drove me crazy. I tried cleaning with alcohol, sanding, burning off all contaminants 3 times then reassembling with extreme care as not to contaminate anything and then attempted to re-bed but nothing fixed the problem.

As a last resort before buying new pads and rotor I sprayed the rotors with automotive brake conditioning spray and that seemed to do the trick to quiet them but braking power was lacking. I was super fed up at that point and just settled with the result.

Fast forward after riding a few months and my rear brakes started to get really squishy. I re-bled the system and no matter how hard I tried bubbles just kept coming out. I checked for leaks and found that one of piston seals had a tiny leak and was pooling oil underneath the caliper (which was likely finding it's way onto the pads and rotor). I ended up getting a warranty replacement, installed it and this one is leaking from one of the pistons too. I'm not sure what I'm going to do now but I'm really fed up with these brakes...
flag holytrails
Posted: Nov 17, 2020 at 15:23 Quote
CorBillionaire wrote:
Check to see if you have a leaky piston that's leaking mineral oil onto your caliper!

I had this problem on a brand new bike (custom built by myself) and it drove me crazy. I tried cleaning with alcohol, sanding, burning off all contaminants 3 times then reassembling with extreme care as not to contaminate anything and then attempted to re-bed but nothing fixed the problem.

As a last resort before buying new pads and rotor I sprayed the rotors with automotive brake conditioning spray and that seemed to do the trick to quiet them but braking power was lacking. I was super fed up at that point and just settled with the result.

Fast forward after riding a few months and my rear brakes started to get really squishy. I re-bled the system and no matter how hard I tried bubbles just kept coming out. I checked for leaks and found that one of piton seals had a tiny leak and was pooling oil underneath the caliper (which was likely finding it's way onto the pads and rotor). I ended up getting a warranty replacement, installed it and this one is leaking from one of the pistons too. I'm not sure what I'm going to do now but I'm really fed up with these brakes...

oh good to know!!! Never know what lurks in the dark!!

Yeah, I've got new pads on the way. I'll look for leaks too though. My old pads are toast after burning, acetone, sanding. dang!!
flag holytrails
Posted: Dec 17, 2020 at 17:45 Quote
update

Switched to resin pads and the world is now a better place to live. And no difference in the power.
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