[See-Fu]

I was at laguna seca this weekend and I installed my PFC pads at home. About 2 hours into the drive to the track my brakes developed a severe shake. I thought I could make it go away by bedding the brakes when I was on the track. I had some strange results. Sometimes I would get brake shake, sometimes I wouldn't. All throughout the day I checked the rotor to look for an even transfer layer. The rear transfer layer is beautiful. It's a nice even gray. My fronts on the other hand has spotting and streaks. Any suggestions on how to fix the shake? Thanks

the brakes are brembos w/ PFC 06 in front and PFC 01 in the rear. It was also fairly cold at laguna seca. I got on the brakes hard enough were abs kicked in a few times

[krisa9977]

99.9% chance that you need to replace your front rotors

[flink]

btdt, got the t-shirt.

You'll probably find that driving on the street for a week with cold street pads will clean the rotors up, so nothing needs doing.

I've had some success cleaning rotors with a flap wheel on a 4-1/2" angle grinder.

Cold race pads clean rotors pretty quickly - they're abrasive. Hawk Blue pads are particularly effective - I know one guy who bought a set for this purpose and they worked. Just drive them on the street for a few days.

Of course, getting the rotors turned will freshen the surface.

Me, I'd start out simple - just put the street pads back on and see if things fix themselves up after a couple of days driving.

[See-Fu]

Wouldn't cold race pads just make the shake worse? I think thts when I first noticed the problem

[flink]

Originally Posted by See-Fu

Wouldn't cold race pads just make the shake worse?

Race pads tend to work in two modes. When they're cold, they work in "friction" mode, where they just scrape away at the rotors. They have a high level of abrasive material to support this. The more abrasive, the better the "cold bite" and the more rotor wear.

When the race pads get hot (several hundred degrees F, which isn't very hot), they operate in "adhesive" mode. Various gases come out of the surface and adhere to the rotor and the resistance comes from the making and breaking of chemical bonds.

If the pads get hot, then the transfer of material from pad to rotor commences.

I think thts when I first noticed the problem

Yeah, I expect that you got the pads hot enough to start the transfer process, but not hot or long enough to complete it. Once you get partial pad transfer, that bit of the rotor gets hotter and tends to remain with more pad material transfer.

Once judder comes, it can be hard to get rid of. I have fixed it a couple of times by just braking maniacally hard for several fast laps, simply blowing my way through it.


As long as you drive gently and avoid starting that outgassing process, the race pads will be good rotor-scrapers.

[edwin814]

i had that problem when i first installed the race pads on my e30 m3. after bedding the brakes, the vibration went away.

btw what car were you driving at laguna? i was hoping to meet you.

[See-Fu]

I was there in a Interlagos blue m3 with 3 other bmws. We were oakes in the same row as a bunch of FerrariS


My guess is I wasn't able to keep te brakes hot long enough on the track. I guess I'll bed them when I get home or Maybe sears point will be harder on my brakes

[alanbmoore]

BTDT. I like that.

I had the same problem with PFC 06s, even with new rotors. I'm starting to think that street tires (PS2) just can't generate enough heat for them. I've taken the pads off, and am thinking about selling them.

I just don't know what to replace them with...

[See-Fu]

I don't think it's an issue with the tires. I believe lightwerkz has brake cooling and he's running them fine

[LightWerkz]

Id upgrade to the pfc01 and use them to remove that pad transfer on the rotors. Should help.