garrett376

Wow, those are some beefy pads!!!

Mark, I just raced with POC at Laguna a couple weekends ago - Laguna is the only track that my 996 brakes go soft and all the way to the floor by about lap 8 of a 12-15 lap race (stock setup, PFC 01's F/R). I can run 1 hour enduros at other tracks (Cal Spdwy, Buttonwillow, Miller) and never have any fade at all. Amazing despite the 60-70 degree ambient air temps, the brakes get so cooked at Laguna. No time to cool it seems.

Good luck!

mark kibort

Yep, that would be nice, but surely more effective at watkins Glen, and even at Sears, at the power and speed they are traveling, they certainly need it. another factor, which is pretty significant....... they are not running 25mins on the track. these rotors are cooked for a couple hours and need to be kept a lot cooler. Plus, its nice to have pads that are 25mm thick vs our 15mm thick pads to keep the calipers insulated from some of that heat!

mark kibort

Again, its not so much the time too cool, its the tremendous heat generated down the main straight and not ever dragging the brakes any earlier than possible. (and low duration engagment when braking) however, if you dont do laguna a lot, there are some tricks to the track to really spare the brakes. You should never get a soft pedal there wiith decent brake fluid. I would guess you are running 1:42ish?
The trick is : long fade-y stab of the brake down into turn 2 with big trail brake (this is where all the heat comes from)
then:
quick stab turn 3
quick stab turn 4
2 second stap turn 5
quick stab turn 6
2 second stab turn 7 (corkscrew)
no brakes until turn 9 quick stab
2 second stab into final turn 11.

What you saw is a little dangerous and a little unnerving for your pedal going to the floor. I had that issue, a few races ago, but it was due to some major air in the system. Once it got fixed... it was much better. (got all of the air out at home, but i had some caliper issues to fix too) But, in my race, it started out bad, it didnt get bad by mid race like you had it happen.

Matt Romanowski

With what you described it's an obvious cooling problem. Put some proper ducts on it. Anything else is a band aid.

stujelly

probably a dumb question but if you are running a 25mm pad compared to what I run in the cayman or cup which is 17/19mm, wouldnt it take longer for a thicker pad to cool down once it was heat soaked?

You know the guy to talk to about the PFC pad is derik dong (sp). He represents their product well and knows his stuff.

redtopz

When we raced scca T1 with the old rules we ran our corvettes with stock front and rear rotor sizes which were about 12.8". I used hawk dtc70's and had good luck with them. Rotor quality and cooling ducts were key factors. Stock rotors wouldn't last a day, but good 2 piece stoptech aerorotors or AP racing rotors lasted a long time. Our cars were about 3250 lbs and 370-380 whp.

Redsled

Mark,
Back when all of the Vipers would race with you and Kent Jordan in that monster EVO wewould have to run additional brake ducting to our front calipers due to the weight of our cars and the speed we would carry into turn two. The Viper is just plain heavy. Some even ran ducting to the rears. As others have mentioned your ducting may not be adequate for that track, but fine for T-Hill & Sonoma. I've attached a pic of the shroud I used. Both a 4" and 3" hose was used to get air to the inside of the of the rotor and to the caliper. During the summer months I still had fade for the last 2-3 laps. I have had good experiences with the Carbotech pads. Best of luck.

mark kibort

\
That's kind of my situation. PFC01s are close to the DTC70s (that I was going to change to next, but got the "expert" advice that the ST41s were night and day better. same rotor sizes and power to weight (close anyway). what do you think the difference between the rotor material, besides 2 piece.......... seems like the stock rotors , might be better for heat disapation, but harder on hub bearings!

I like the pics! thanks.... I can do that, and have to find some inlet to carve out to augment the cooling situation. whats that CF piece that mounts toward the rotor?
Thanks..... ill see if the cooling helps. I have a couple of months til the next SCCA race, so I have time to bolt something together and test.

mark kibort

I don't know if its that obvious, because it only happens into the one turn at laguna. But, Ill have to try and see if those 12.6" rotors can slow the car enough and not groove the rotors with all that fade, and the extra pressure applied that didn't do much in the fade condition. however, if there is no fade with the ducts, It wont force additional pressure. so, it might work and will try it.
Im not running the 25mm pad, I can only run the 15mm pad. My friends with the 15" rotors have the thick endurance stacked pads.
Ill have to talk to Derek especially to see if he thinks he PFC01s are as good as the ST41s. I liked them, but I should address this cooling problem first, and eventually, adapt my set up for a larger rotor, and maybe some larger calipers too.

Redsled

"whats that CF piece that mounts toward the rotor? "
That's a Viper CC and ACR-X cooling shroud that can be ordered through Dodge Viper Race Headquarters. There are many variations of that piece to fit other applications. I would try the following site. Lefthander Chassis

flink

Obviously you're exceeding the pad's max operating temperature into T2. I can't find a spec for the PF01 but the DTC70 is 1600F and the XP20 is 2000F, which is peculiarly high.

I've found the DTC70's to be a bit marginal in my 240hp/2700lb thing. I'd get occasional pad fade into thunderhill T14. Replacing the Coleman rotors with Wilwoods (slightly heavier, more vane area) was sufficient to prevent that.

It's hard to say without knowing the PF01's MOT (ask Performance Friction?), but perhaps switching to XP20's will fix this. I have used one set, liked the feel of them a lot, but they're expensive and wore at twice the rate of DTC70's.

However using higher temperature pads is a palliative. The way to reduce peak temperatures is to improve cooling and/or to increase rotor mass. Probably switching to a two-piece rotor would suffice - they are much much better than single-piece ones.

Veloce Raptor

IMHO, the PFC 01 is so much better a pad than the DTC 70, and the newer PFC's (like PFC 11) are better still.

mark kibort

Thats what i heard too, mostly from you and the folks here on the boards.
I still think that even with better air flow, that last few feet of the braking zone, has SUCH huge forces and heat on the rotor, i dont see how it would help that much. its seems like an very very fast heat burst issue, due to over brake pressure in the "Fade" zone. which basically just adds heat with no additonal braking force..... and the agressive pads, just end up "digging in" and just grooving the rotor. (my theory). If there was a pad that could handle that extra heat and still produce stopping power, that would be a solution too.
Ill try the better ducting before laguna before i get the larger diameter rotors and see if that helps

as i mentioned, running 1:39s all day long, i didnt have much of a problem with fade with 330rwhp and 3000lbs. But with the 10mph extra straight speed, and using the same braking points, the fade is so bad, i need to release and brake again to regain bite just before turn in. If i was just to hold the pedal down, i would drive straight off the track by never slowing to fastest turn in speed.

Peak temps will also be reduced with a larger diameter rotor. 15% more torque, or 15% less pedal pressure for the same stopping force. that would be huge. two piece reduces rotor mass, vs a stock rotor actually with a lot more surface area and mass to dissipate heat. I think a pad with higher temp abilities would be a bandaid as you suggest too, but i cant imagine a pad with more grip than the ST41s. But, as i mentioned, i heard the DTC70s were the best, but some "expert' said that was old fashion technology compared to the ST41s.

thanks... ill check it out.

kurt M

This^^

All the typing, pad swapping, wrench dropping and overthunking can be sumed up in 2 words. Increase cooling.


The stink from new pads is not "the resins cooking out" it is the paint.

I am running what would be stock brakes for a 1969 911 on a car with a 993 motor in it. I also have monster air ducting fopr the fronts and they run cool fade free and the consumables last forever. I was able to roast a set of pads and rotors on the same brake setup on a 2100 pound 90 HP 912 with no cooling. The little weedy ducts and hose zip tied to stuff does not work all that well. You need some real air from good sized ducting fed by good sized intakes. Get the air there and everything will work better and last far longer.

Mahler9th

Hi Mark.

I have not read every post in this thread, but...

Like others, I believe that you should examine your cooling set up (if any) and work toward optimization. Even my 1900 pound GT2 car can have brake challenges at Laguna (I had some at RR IV). It is just a hard track on brakes. But you may benefit from optimization at other tracks as well.

A million years ago when I had a 3000 pound 300-350 bhp car (you remember that car I am sure), I removed the driving lights and installed cooling ducts, feeding air to rotor centers with the age-old, time tested Holbert Cool Brake system. Old timers will remember that product for sure.

Worked great and reduced the need for fancy pads and fluids. With that car I went through a bunch of steps which included using temperature paint to see what was happening. I even considered water-cooling, but that was silly until I had the ducting in place.

On my current 911 race car, I also duct air through the front bumper to strut-mounted carbon-kevlar backing plates I made in my garage. All of the air goes to the center of the rotors. This is old school 101 and I think forms a proper basis from which to start.

For front-engined water-cooleds, I always suggest investigating a change to a more aggressive factory-style proportioning valve once cooling has been optimized. That is, for those cars fitted with such a valve when built by PAG. Back in the day there were about 5 choices of factory valves, with the most aggressive rear bias available from the 965 cars. In some cases, some configurations of cars could remove the factory-style valve entirely, getting the rear brakes to take on more load, without he risk of rear lockup.

These two steps, along with decent pad/fluid choices were, and likely should still be, SOP for these cars. Then if that is not enough, bigger systems (rotors and calipers) and so on.

Hope all is well with you and your family.