Jim Devine

AP sells temp paint that turns color at certain temps so you know how hot the rotors & calipers are. Until you know, it would be hard to pick the proper pads.
This short article from them explains temps & towards the very bottom under the msds specs
states that grooved rotors are a result of excessive heat.

http://www.apracing.com/Info.aspx?In...&ProductID=976

An excellent video:

http://www.essexparts.com/learning-c...rs/post/Bed-in

It's long & very well done-


AP has been in the race brake business for over 50 years- they have extensive knowledge.
If your front temps are way higher than the rears,
the rears are just along for the ride.
Until you know the true temps, anything else is just a guess. Hope you can get to the bottom of the problem.

RacingBrake

We have just acquired the related spindles and calipers, upon receipt we will give a complete assessment and propose a solution to resolve 928S' brake issues.

RacingBrake has a proven record in providing solutions to brake issues on most popular race cars from small/light weight car like Honda S2000, up to fastest/heaviest super muscle cars such as Nissan GT-R.

What wheels sizes most of you are running; As a general guideline 330mm rotors kit can be under 17", while 350mm rotor kit would require 18" wheels.

IcemanG17

MK
Problem #1..............you didn't break in the pads correctly
#2 You didn't use new rotors, change the type of pads, then you must change the rotor for it to work correctly.
#3 You didn't install the rears as a matched set
#4 What bias bar are you using? 32? 55? Please don't say stock 19? That would explain lots
#5 What about boiled fluid? Is it spitting?

A true two piece setup like Racing Brake offers and properly broke in pads will solve all your issues.

Honestly the 322mm GTS setup with those pads will work just fine at your power-weight. Seans racer 52 has the exact same brake setup and I ran on Casper GTS brakes, ST41 front ST43 rear. It will suck the eyeballs our of your head.....It runs, just with around 220whp...try it....

I gotta ask. Why do you ask for others opinions-experiences to help you out, then totally discount or try to disprove them?

mark kibort

its excessive heat ,based on my knowledge and experience. the facts say, same braking performance. a little more initial bite, but rotor grooving where the brakes were forced to overheat at the end of the main straight of laguna. I can almost gurantee it. Ill put the temp paint or stickers on and see what the calipers are seeing, maybe the paint on the rotors as well. the fade is something ive just driven around and it has been marginal at the other tracks. no other track slows the car down from 130 as laguna and you need to be near 3000lbs or greater, and that means near 400rwhp to have this effect. If I wasn't overdriving the car to get the best lap time in this area, the pads would be fine. I suspect , the rotors are too small.

im running true 18" wheels.

the fluid is stoptech. one of the better fluids out there. MUCH better than superblue ATE. its not boiling.
I broke the pads in very very moderately. NOTHING compared to even a mild lap at laguna during my first two practice laps. Ive been doing this a long time. I did this technique with pagids and the rest, and all it does is help reduce the time at the track, vs a brand new pad. im not killing it as Jeff has thought .. im simulating a very mild lap. they looked brand new when I was done. in fact, it was the least ive ever done on the break in procedure. I simulated a lap, based on time and speed . (e.g go though the gears up to 110mph, slow the car down to 60, accelerate back to 110, down to60, a few times. I added a throttle on downshifts, which simulates downhill and just when I feel like its fading, which happens quick, I back off)

again, what does it matter what my rear pads or rotors are?? im always going to run to the limits of the TIRES, not the brakes. if the rears are better, then ill stop better, its not going to change ANYTHING on the fronts. if they can be overworked, then they are too small. again, ive driven andersons car at laguna. it has NONE of these issues, and if he had no rear brakes at all, it would have NONE of these issues. I have tiny (compared to real race car brakes) rotors! 12.7" is even smaller than the Stoptech st40 set up that ran on the WCTouring cars. they had 14" rotors.

the only difference by using a rear brake system that is better or more biased, is that you will slow faster. remember, when you slow faster, you pull more decal Gs. as it is, im over 75% weight bias to the front under braking. does it matter what rear brakes can do on 325lbs total acting on a rear wheel (750lbs overall in the rear underbraking)? its going to help, as long as it doesn't lock up the inside rear under trail braking and that's part of my style , NOT to do. watch the video of the NSX with poorer braking performance and rear wheel lockup. that's what too much rear bias can do.

mark kibort

great video !!! Jeff, watch it! Please so we can discuss more. thanks Jim. But, its more about street pads. racing pads, are very abrasive and don't seem to leave that layer of pad material down. I do think there is over temperature going on here and the only solution is a larger rotor IMHO.

I have always controlled my heat into the disc, process. (and also for transm,and engine) and proof is in the fact that my rotors have lasted a long long time, with NO warping, no uneven wear or uneven deposit of pad material. I know what that looks like, and it seems be have done correctly.
the rotors have not cracked prematurely, and I did something on the street that barely wore in the brakes. it was a fraction of what I did on the track, and even on the track, the first few laps I was very aware of the temps of the rotors and continuing a bed in process that these guys would have been proud of.

in fact, bed in procedure was probably better, because it was done at higher speeds. they cant recommend 100mph, because that is breaking the law. I always backed off after fade, because that is when the heat is high, and you are doing the beding in process correctly and I waited until they got some cooling before I would do a cycle again. the things I did were identical to the video.
proof also by when I showed up to the track, during practice. and some mild laps to start, the pads killed the rotors, grooved them, and turned white from over heat. only 1:39 lap times for one lap at laguna, while the others were 1:41s etc and were not pushing that hard.

Rob Edwards

Mark, there is no bias/proportioning valve in the Zombie, so no limit on how much pressure the rears see under heavy braking. Judging by the color of the backing plates on the Pagid blacks I pulled out of them, they did plenty of work...

Jim Devine

Early in the video he discusses rotors that they burnish (break in) for some nascar teams. Also, about the last 5 minutes are more competition oriented. Takes watching it more than once to get everything out of it.

If you go to the site of the video, below the video is a detailed print article with pictures- to see it scroll down after this comes up- don't click the video- might be worth printing so you can re read it as necessary.

http://www.essexparts.com/learning-c...rs/post/Bed-in

James Bailey

What is missing is the ABS unit.....something which Kibort still has as I recall. Which makes all the talk about trail braking, threshold braking , and possible fade rather amusing since what he is "feeling" could simply be the ABS kicking in as the REAR brakes or fronts approach lock up...Having the computer maximize/ control the braking allows you to do all kinds of interesting things. That was one of Anderson's comments about running the 911 cup car with ABS was how you could be on the brakes and STILL turn !! Dive under cars under hard braking and live to tell about it

and Rob I think that small cylinder hanging on the brake lines where the ABS unit used to be is the proportioning valve......

Rob Edwards

Hmm. I thought that was just an inline female/female coupler to tie the lines together. When I first bought the car from Mark I asked him about what proportioning valve he used and he said that over time he went higher and higher as the front brakes got bigger and bigger, and eventually got rid of any limiting valve. But maybe I'm mis-remembering. Will doublecheck.


EDIT- talked to Mark A, that's just a coupler. No bias valve.

mark kibort

I ran all the world challenge races without the ABS Ive run many with it, and many without it. Comical you are now going to teach me about trail braking, Jim. Really! threashold braking with or without ABS is very easy. ESPECIALLY with old ABS , because its obvious when it kicks in. I used to use it for early warning detection to prevent lock up, because when it engages, the car slips down the track like 50% braking. 928 ABS I NOT racing ABS. so , its very obvious when it slowly growls at you releasing the braking force, quite dramatically. NOTHING like the ABS on most modern cars, let alone on a Porsche supercup car. you can just stand on the pedal and the brakes do ALL the work. all you need to do is steer and know when to engage the brakes!

so, yes, I dive hard into turns, WHILE braking and its one of my advantages against some of the competitors. I also do a few other things to lighten the stopping load on the brakes at the expense of tires.

let me just clear something up Jim. when im into turn 2 at laguna, I have a very aggressive threshold brake a the beginning of the braking zone. by the time I get from 130 down to about 70, the brakes are fading and I start to press as hard as I can. I then aggressively turn in, while threshold braking. something that gives a lot of my competitors fits. in fact, one time I tried to really press even harder to see if I can engage ABS, and there was not even enough force to do that. the last few weekends, ive pulled the fuse on the ABS , so I didn't even have it running for your information. Found out I had a broken wire at the spindles. Again, I know the car and the feel of the car extremely well. ABS is basically a warning light with noise, feel and action. it doesn't do much of anything but increase stopping distance and keep from flat spotting a tire If you are not careful.

Pfc. Parts

Very useful. I've never been fond of ABS and spent quite a few years road testing it. This makes sense out of a feature I've never been able to make sense of before. Next time I'm on ice I'm going to review my impressions with this one in mind.

Thanks,

mark kibort

im sure they did. it doesn't change the fact that I could into the brakes as hard as I could, without tire slip and not have ANY fade. the reason, is due to his rotor diameter and possibly brake cooling system. I don't think just because you have a bunch of rear bias, that suddenly you don't cook the fronts, especially since so much more braking force is done by the fronts. keep in mind, that the rears are always a little equipped with ABS, in that the wheels are tied to the gear train. So, its like built in abs for the rear, which also desensitizes the rear . that's a lot of inertia tied to the rear wheels at the axles. his car with much larger , slicks in front also helps with slowing the car down with turn in and trail braking.

yes, I watched it several times. its the process that ive perfected for breaking in pads, that not many of my compeitors do. (none of which have had this grooving problem with their rotors) Ive been much more methodical than most in braking in pads. what I do on the street is a fraction of what even a mild lap on the track is. keep in mind, I can run a 1:47 at laguna with out even touching the brake pedal. with the increased speeds down the main straight, to over 130mph, its a huge burden on the brake system to get a 3000lb slowed down. the 3400lb mustangs are doing, it, but they have PFC-01s or 13s now, and 14 " 2 piece rotors. in driving the fast M3s, at 2800lbs, and near the same top speed as the old holbert car, there as NO fade at all in the system, build with the Stoptechs and 14" rotors. that's a HUGE gain in leverage point, with a LOT less pedal pressure to gain the same stopping force.

you see this is something Jeff is not thinking about. with a 14" rotor vs a 13" rotor, you are getting near 10% to 15% greater stopping force for the same pedal pressure. (over the 3" pad surface). this is HUGE.

I'm producing the same pedal pressure with the new pads as before with the old pads. I'm stopping at the same rate of decal. the pads are just to aggressive for the job, to slow the car down without destroying the rotors.

if I get a more aggressive rear pad, it will make my stopping power increase slightly to the factor that the 25% of the weight over the rear wheels can slow the car, vs currently. BUT, I'm still going to ask the front brakes to stop the car at the limit of the tires, not considering the rotors heat condition. the rotors and pads should be able to do this. it seems like the ST41s are too aggressive for a smaller rotor at this rate of decal. like I said, my gingerly driven lap 1:40ish, resulted in groove rotors. that session could have been considered a burnishing , or break in lap. you cook the pads slightly, don't get them white hot, but transfer material to the rotor. mate the surface well to each other. And then qualify with perfectly set up brakes. I did this, and the rotors were chewed to death. again, I've done the exact same bed in process as the video, and what I've done for all the pads in the past. Performance friction PFC -01, Black Pagid RS14, RS-4 Porterfield, and now ST-41s

so the bottom line, is that If I had rear brakes that were more biased, at the limit of the fronts, I would slow to brake release point, a fraction quicker. sure, that would lessen the load of the front brakes due to the extra time im using them. BUT, they shouldn't be at such a limit that the rears should be the limiting , or destructing factor. an increase of power to the engine, a downhill straight, or an increase of approach velocity due sticky tires or lighter weight, would more than increase front brake threshold engagement time to coutner act what im seeing on the car with less rear bias.

and yet again, the grooving was present from the first practice for a bedding set of laps, with lots of rest between laps. 2 hard, 1 rest , 2-3 hard, etc. (even after a pretty decent bedding process on the streets before hand).

mark kibort

I drove for so many years without ABS, when I got it, I was excited to use it, when I used it, it was nothing more than a flat spot safety net. very useful, if used for this purpose. in fact, panic braking, where most folks use ABS, is kind of dangerous. I almost think skidding is better at braking , its so bad (at least on asphalt) all kidding a side, if you did have a panic stop, the ABS would be better than lockup, but completely useless on the track.
and contrary to Jim's assumption..... I'm not engaging ABS...... maybe during the next race weekend, I'll take a video of full abs engagement down the main straight.