2008 135i BMW Performance Rotors and Cool Carbon pads = squeal and grinding

[pablom2c]

Hi,

I'm new to the forum (only been reading for some time) and need your help please. Four months ago I bought a used 2008 135i with 30,000km/19,000 miles and the car needed new brakes. I only use the car on the street (just a little spirited).

So I decided to buy new Cool Carbon pads S/T (due to forum recommendations I read about their performance/low noise/low dust) along with new genuine BMW performance rotors (drilled and slotted). This was around a month ago, so it's been already around 800km/500 miles after installation.

The first week or two after installation I did not get any noise or grinding, but around 2 weeks and 350km/200 miles later I’ve started noticing break squeal more and more often and louder. Also sometimes when coming to a stop with the brakes hard on the pedal I can feel and hear like some kind of grinding on the front of the car. I don't think the ABS is activating because no lights are flashing? The grinding cannot be felt on the steering wheel, there’s no vibration or pulling to either side (wheel bearings and alignment are fine). I can also hear a hum when braking hard (I think this is due to the drilled and slotted rotors right? It's my first time with these kind).

What could the problem be for the squeal and grinding? I have already done numerous bedding procedures following Cool Carbon's recommendations on their website (repeated hard stops and letting the brakes cool). All brake components are correctly lubricated and installed, so my mechanic is very confused and can’t find the problem? He has disassembled the calipers and pads with me watching and applied lube/grease twice and everything seems to be fine and correctly installed. I even tried disconnecting the brake sensors but the squeal was still present.

My mechanic has now recommended to once again change to new pads but this time go with original BMW pads because he is blaming the Cool Carbon pad material causing the squeal.

Besides the noise and grinding the stopping performance doesn’t seem to be affected and seems very good.

Do you have any ideas what could be causing this or other things to check to finally fix this?

I have already read many threads similar to mine but can't find a specific fix and don't know what else to try besides new pads.

I really appreciate your help before spending more money oonce again on new pads, thanks!

[tracer bullet]

I was going to suggest bedding the pads in again but it sounds like you've already done that. I had a higher performance pad on my last car and after a few weeks of daily driving they would start to squeal a bit, but a few hard stops always put an end to it.

The two things after that that come to mind would be the pad installation and pads themselves. There are a variety of ways pads can be incorrectly installed (missing clips, lack of the anti-squeal goop (if it was needed, it isn't always), whatever. Someone who's changed their 1-Series brakes may have detailed input there (I have changed plenty of brake pads, lines, calipers but not on this car yet).

The pad would be the next thing to look at. The drilled / slotted rotors will cause interesting noises (I'd say it's more of a whizzing sound than a hum caused by the drilled holes, the slots not so much). But since most all rotors are simply cast iron, gut feel to me is that the pad is the bigger variable.

[chris82]

I had Hawk HT-10 motorsports pads on for a week before I went to a track event, and they squealed like a bitch on the street, awful squealing and some occasional grinding; what fixed it was really hard braking until I got them heated up and the squealing went away

[pablom2c]

Thanks for your comments, I guess I will keep trying with more hard braking for now.

[pablom2c]

I just wanted to update you guys on the situation: I had contacted Cool Carbon about my problem and after trying different things with the current pads and not getting rid of the noise, they are now shipping me under warranty a full front pad set. I hope this fixes my problem! Just wanted to share with you that they are looking after their customers and offer great customer service.

[Ihave1]

I have the same setup with drilled + slotted rotors and cool carbon pads. Mine are usually dead silent with the occasional squeak when they are cold. It goes away after stopping once. Hopefully your new pads fix that issue.

I do however notice the grinding feeling. I think it's the to the drilled/slotted rotors interfacing the pads. Since its not a completely smooth surface you get the grinding feel in the pedal. I wouldn't be worried about that.

[Chandon]

Eh.. I have cool carbons with drilled & slotted rotors and they're not great. Followed all their bedding instructions and they've been squealing quite loud for about a year now, along with that I also get the "grinding" feel. Still a lot of brake dust too.. Would prefer OEM pads tbh.

[pablom2c]

Thanks for your replies. I guess from your comments then that the "grinding feel" and "hum" must be a characteristic of the drilled and slotted performance rotors, and is not related to the pads. That is good to know.

To be honest I'm quite happy with the braking performance of the pads and in my experience they are low dust, so I will see if the noise disappears with the new pads they are shipping.

[Ihave1]

They definitely work better once heated up and although they are lower dust than OEM they still produce plenty of dust unfortunately