Sobe_Death

I am having an issue where my brakes will squeal sometimes driving at 20-40 mph and when I turn left or right. Pads are Carbotech Bobcats on blank rotors. One of the knuckle assy's is brand new, the other is stock, so I doubt it's both wheel bearings. I also had a problem with cooking the Permatex ceramic caliper lube (purple goop) so I thought that the pins might just be losing lubrication causing the caliper to stick and not slide properly.

Fixes attempted:
-Sanding pads to remove any sign of glazing
-Disassemble the caliper and regrease caliper pins, new rubber boots
-new rotors
-I switched from the purple goo to just plain moly anti-seize compound (2100 degree temp rating)

Any ideas on what else to try?

Sobe_Death

perhaps I should mention that when I do these "fixes", the brakes stay quiet for about a week of daily driving. Then the noise starts back up.

Lakersfan

Sobe:

I reached out to my friction friend who is "really" a brake expert and here is what he said:

"Performance pads are more prone to noise than street pads. Nothing was mentioned about shims. High quality rubber coated shims would help. If not, change friction to StopTech Street Performance."

Disclaimer: You can guess who he is affiliated with.

One opinion. Let's see what else pops up.

theblackpearl

try smothering the back of all the pads with the lube and everywhere the back of the pad mounts to also.

this will collect a lot of dirt on the caliper though

Sobe_Death

I used new OEM shims on the pads with lubricant on the backing plate and between each of the shims. I also lightly lubed the spring clips.

My next try is going to be a remanufactured caliper. Maybe the piston is sticking?

theblackpearl

try being very very liberal with lube. worth a shot before you get a reman caliper.

Sobe_Death

That's what she said

Sorry, I couldn't resist! My problem is that if the caliper is sticking, that can't be happening. I get my brakes up to some pretty high temperatures on the backroads and if they are dragging that's just no good.

BrakeExpert

I'd check the calipers physically to see if the pistons protrude. You may want to check to see if the rotor is balanced, like are your retaining screws loose at all?

Shims help, they really do, but when people put that grease on the piston or caliper's teeth, I don't know what they are trying to achieve. The anti-vibration compound goes between the shim and the pad. I've run metal race pads, and they make noise when braking. Your issue isn't that. Have you ruled out the axles as a source of noise? You know the axle nut torque spec was revised, as my friend's S2k was making noise when the rear axles were torqued to like 150lb-ft, but the new specs are quite a lot more. Have you checked the calipers for modulation? Like mounting em without the pads and making sure they slide back and forth? If one of the slide pins is bent even a little bit, it can cause noise issues. How are the rear caliper boots? Is there any issue at all with the e-brake causing maybe one or both sides to be be engaged at all? Have you checked the ball joint on that new knuckle? Lastly, what sort of noise is this? Where does it sound like its coming from? both sides, front or back? Any wheel vibration?

Sobe_Death

Hey Mike nice to see you chime in. The issue is on both front wheels, though moreso on the passenger side. I have not noticed increased dust or heat from either single wheel. When I turn right or left, it is a low-volume, high-pitch squeal. The calipers do slide back and forth, however they are reluctant to do so every time I check out the problem again; once the pins are regreased they slide freely. The pistons seem to be retracting and extending as they should; when I remove the calipers I am able to easily fit them back over the pads. The rear caliper boots are new as well (<9 months). There is no e-brake drag, and I never engage the e-brake since it is barely useable. Zero vibration or steering wheel oscillation under braking or otherwise.

BrakeExpert

Don't know if this helps. I had a pair of Integra calipers on my car long ago. The slide pins were slightly bent. Like if you finger tightened the bolts, it would be fine, but when you tightened the bolts (caliper to bracket) it would suddenly become harder to slide, because the pin was bent at such a slight angle that it could rotate back, a tiny bit.