wjk_glynn

Hi folks,

After my first track day at Laguna Seca in years (which was brilliant fun!), it looks like I "cooked" my brakes.

By the 4th session (and definitely by the 5th) they were:

• Making grumbling noises
• Exhibiting noticable vibration when braking from high speed
• Pedal was a tad soft (not bad, but enough that you'd notice)

A few months before the track day, I'd had my mechanic refresh my brakes by installing:

• Slotted Zimmerman rotors
• Pagid blue "sport" pads
• ATE Super Blue brake fluid

I assumed that would be sufficient. But in hindsight:

• Either I didn't bed the pads properly in the first place (though I believe I did)
• Or more likely I overheated the brakes on the day and caused uneven brake pad deposits on the rotors.

So I'm likely to change over to Pagid racing pads (a friend is recommending Pagid Orange in the front, Pagid Yellow in the rear -- comments appreciated). [Edit: Fixed typo about what was recommended in front/rear]

But as regards removing uneven pad deposits (assuming that's the issue), StopTech's excellent White Paper site suggests trying:

• Scrubbing the rotors by temporarily fitting "semi-metallic" pads (e.g. Hawk 9012) and performing a specific brake-cycle procedure
• Vigorous hand scrubbing of the rotors with garnet paper
• Blanchard (i.e. rotary surface) grinding the rotors to resurface them

So I'm trying to figure out if it's worth the hassle of even trying those options as replacement rotors are not hugely expensive (e.g. ~$105/each from Paragon).

Have others have been successfull (or not) renewing their rotors once they started juddering?

Thanks.

Karl.

PS: If I do install Pagid Orange/Yellow, can I switch back and forth between them and the blue "Sport" pads for street use without having to bed them in after each swap?

Swagger93

I've done the vigorous hand scrubbing procedure. Your arms will probably go numb, but it worked for me.

pontifex4

I've read that white paper, too, and I just can't see helping the problem by installing temp pads, or doing it particularly well by hand. I think the only thing I would really trust to get a proper surface back (assuming that is, in fact the problem) is having them turned. Can you feel any grooves in them? Also, I've yet to find a place in my town which will turn drilled or slotted rotors.

Van

Probably no bedded properly. Watch this video: http://www.essexparts.com/learning-center/Bed-in?v=0

I've cleaned up rotors with a wire brush on an angle grinder. That doesn't take too long.

Pagid Oranges (and Blacks) are great pads that perform really well at the track. However, I find that PFC (Performance Friction) bed in much quicker and are unlikely to leave thick deposit spots on the rotors...

Re: your soft pedal - when was the fluid last changed, and what fluid are you using?

Oddjob

Most Pagid pads, including the oranges tend to smear deposits onto the rotors when heated beyond their designed temp range. Blacks dont and I would recommend running blacks versus oranges. Certainly would not run blues hard on the track.

The deposits will often wear off over time (on the street). Or put on a race compound pad next time on the track, and that will get it off too. Can take the rotors off and do some hand or power sanding on them. I would not have them turned, and wouldnt replace them until they are worn out (cracked thru).

You can swap back and forth between street and track pads, without issue.

wjk_glynn

There does seem to be surface irregularity according to my finger tips.


Thanks.


ATE Super Blue was put in (at the same time as the new rotors and pads) 1-2 months before the track day. Nothing agressive between the installation and the track day.


Good to know.


Thanks all.

Karl.

mikey_audiogeek

Hi Karl,
Factory rotors are better than Zimmermans. You would probably notice the difference. Were you able to cool the brakes down properly before pitting? If not, that can cause material transfer.

By the way, great writeup of the problem and symptoms! I'd be keen to hear your final solution - I'm running factory rotors with Pagid Blues and 968 cooling ducts.

Best,
Mike

wjk_glynn

My mechanic said the exact same thing. I wouldn't have thought that (i.e. cast-iron is cast-iron), you learn something every day.

I did the usual cool down lap and took time wandering around the paddock before finally parking after each session (making sure not to set the handbrake).

I had new control arms put in. I wonder if they can be retrofitted with the 968 cooling ducts.

Karl.

Oddjob

The coefficient of friction drops off severely when pads are overheated, normally called brake fade - this can give the sensation of a soft pedal.

Porsche rotors are better than zimmerman - longevity, they last longer than the zimmerman rotors. There will not be a difference in pedal feel or difference in overheated pads depositing material on the swept area.

968 control arms superseded 944 arms 18 years ago. So the only late offset new arms available from porsche are the 968 arms and the 951 M030 arms. Depending on which ones you put on the car, you very likely have the mounting points for the lower 968 brake scoops.

Norm Swanberg

Did you warp the rotors or just get stuff from the pads built up? If they are warpped I think they are done for. I warpped a set of not very old rotors and was told to heat cycle new rotors. Brake hard at 40, let them cool, then 50, 60 etc. I have not warpped rotors since.
Norm

wjk_glynn

Hi Norm,

I believe uneven pad deposits. The reason I say this (and I should point out I'm not an expert by any means) is because StopTech claims warped rotors are a myth:

http://www.stoptech.com/tech_info/wp...rakedisk.shtml


I followed Pagid's own procedure described here:

http://www.braketechnology.com/brakepadbedding.html

Karl.

Norm Swanberg

Karl,
I also am not an expert by any means. Before throwing away not very old rotors I took off the wheel and put a screwdriver or something next to the caliper just touching the rotor. I turned the rotor and I could see that the rotor was uneven. I am not saying I know more than Stoptech, but you might try what I did and see if the rotor is wobbly.
Norm

xsboost90

i used to work for a place that turned rotors- warped rotors is definitly not a myth- ive seen some really uneven rotors - that being said if they are warped get new ones. Cutting them down makes them too thin and they get hot much faster, warping more. I have zimmerman crossdrilled rotors and they are starting to crack up after about a year.

mikey_audiogeek

The factory discs have much better and more detailed internal finning with greater surface area. The casting quality is also much better. It looks to me as though Zimmerman carried on making the "original" discs after Porsche superceded them. Porsche upgrade their parts more often than people realise.

I would also bet that the Porsche discs have a much closer tolerance on material spec and probably have some additional (costly) heat-treatment steps.

My Porsche mechanic said that in his experience OE (factory) discs last 50% longer than OEM, and that matches my experience as well. Factory discs for me from now on.

Don't worry if your suspension arms don't have the attachment lug, you can get around this with a little improvisation and a handful of cable ties...