My first question is: What safety equipment do you have? Roll bar? 6-point? Racing seat?HANS?

How many track days do you have under your belt? As you get more experience, you will recognize that passing much faster cars anywhere but in the upper/instructor group usually means they are driving crappy, not the other way around.

HP alone does not a track car make.

What upgrades do you have? What suspension do you have? ARBs? How are you set up? Alignment? Cooling? What tires are you running? Unless you are adding weight to your car, your braking situation isn't much different than everyone else, SC or not.

Also, why do you think a supercharger all of a sudden means you are driving harder than others/factory specs? I've driven students bone stock cars in the yellow group (intermediate 2) and was able to pass virtually everyone, upgraded or not. Stock 996/997s are pretty fast right out of the box.

As for my car, no it isn't supercharged. But I wonder why you think others must have a SC to have an upgraded suspension or tires. Odd. I'm upgraded more than some, less than others. I would bet I'm right on par with the track junkies here.

Also, I've run more tires than I can count, including various streets, Toyos (RA1 R888s), Michelin (Pilot Sport, Pilot Sport Cups), Hoosier R6s, Hoosier Slicks, Dunlop Slicks, Yokohama Slicks, and I'm sure a bunch of other crap I can't even remember.

Anyhow, feel free to post some track vids when you get back out.

-td <-- already on my 4th track weekend this year...

 

I have a roll bar, 6 point harnesses, GT3 seats, and arm restraints.

Right now the car is making around 435ish to the wheels. Up from around 275 to the wheels when I first started dinking around with it.

As far as suspension goes, Bilstein PSS9's with GT3 sways. Tires... Dunlops. Yeck.

Again, I'm no track star. I'm a complete novice. And I'm certainly not implying that I'm some sort of spectacular driver. My point was that I was passing cars far more powerful than my car in stock form on the straights. Therefore I'm carrying way more speed than what my brakes were designed to handle on the straights and corners, as evidenced by me overtaxing the brake system on both days to the point of failure. And yes, my car is heavier than stock because of the addition of 19" wheels, the roll bar, misc stereo equipment, the supercharger, etc...

I never said you need to have a supercharger to upgrade the suspension or brakes. What I was trying to point out is that my car is unbalanced by me not upgrading the brakes after doing the suspension and engine work. I never noticed it on the street but it became painfully apparent on the track. I had my car tech'd before both track days with complete approval. The fact that bone stock 996's ran all day with no problems and I'm boiling brake fluid and destroying pads ought to say something...

Besides, if my stock brakes were adequate then why don't TT's come with the same brakes I've got? I'm running 100hp more than they do so they should work fine, right?

 

DD, Let us know how your setup works at the track.... if you still have any fade issues, maybe it was an isolated incident since your MC was on its way out.... Ive never had any issues with my brakes setup (stock, ss lines, blue liquid, sports pads, rs brake ducts). In fact at the Glenn, at some parts of the track my brakes squeals (meaning that it is cold). Our track session run 20-30 clips 4x/day.... the brakes hold up really well....
As for the TT comment.... they are like 300-400 pounds heavier than ours. But, then again your cab is prob just as heavy.... so you might need to step up.

 

I've had my car corner balanced. It weight around 3450ish. A little porkey That was pre-roll bar and seats. I'm guessing they canceled each other out though as the new seats are really light compared to my stock full power ones.

The first time I went out there it was with stock pads, regular fluid, rubber lines, and the factory ducts. That obviously didn't go well as I went home in a tow truck.

The second time it was with all the same brake equipment except for the new master cylinder and upgraded fluid. It was better that time, but I still ended up with an enormous amount of pad wear for one day and eventually had complete failure.

Except for the ducts (I'm running the GT3's), it sounds like we have a very similar setup now. We have an event coming up soon. I feel pretty confident that the stainless lines, sport pads, and ducts should help keep things in line to make it through the day with no drama.

 

Most telling is how Porsche abandoned the 996TT brakes in favor of the GT3 sized brakes.
DDs brakes are NOT of a high enough capacity to handle what his car *can* do on track.

 

Which brakes are larger? TT or GT3?

 

I asked Craig: 997 GT3, 997 GT2, and 997 TT all the same - 6 piston
996TT smaller, middle between regular 996 and 996GT3, closer to regular 996 and that is why they have problems when used hard.

 

That makes sense.

I had no idea the 997 GT's and TT all used the same brakes.

 

Excellent! I have great respect for those that upgrade safety before/with performance!

FWIW, you will find out that the front GT3 bar with the short tarett links is not an optimal track solution.

I'm not going to get really technical here, but the long and short of it is, your system is probably adequate given your application. Although a typical response to overheating brakes is to want bigger ones, getting them is often overkill and a waste of money. Keep in mind, you want brakes that are *just* good enough for your application, and not 1% bigger. That is, you want the smallest calipers/rotors that can survive your application. Getting a braking system that is too big adds more unsprung weight and adds substantially more rotational mass.

Here is some some high level info. If you have any questions, feel free to ask, as I'm sure many others can chime in with relevant info.

1) You've don't indicate that you need more stopping power. That is, apparently your car stops just fine for a few laps, but then your brakes fade. THESE are symptoms of too much heat, not necessarily brakes that are too small. Most people think, bigger brakes give me more pad surface area and this is better for stopping, right? Well, actually, pad size is not really relevant in the brake equation. What you get with bigger brakes is more torque and a bigger heat sink. But with bigger rotors, you need to balance the whole braking system, not just one piece (i.e., just the front). You can STILL overheat the system with big [unbalanced] front brakes since your brake bias will be front loaded (more front torque) - AND this may actually increase braking distance as well as produce more heat in the system due to premature ABS engagement. Long and short of it - bigger brakes are not always the right solution.

2) So, as you have come to realize through application, your stock setup is not up to the task of repeated hard braking. But this doesn't necessarily mean that your entire braking system is inadequate. What you need to do is to reduce/dissipate heat so your system will operate effectively without fade, aka manage your brake system thermal capacity. As you know, rotors act as a really big heat sink. Energy (forward motion) is converted into heat through friction between the pads and rotors. Your system is designed to dissipate heat by flowing ambient temperature air over braking elements. Too little dissipation results in an overheated system. Pretty simple really.

Once thing to keep in mind is that stock cross drilled rotors have (probably) 25% less material than solid rotors - maybe 30% less. That's 25% less metal to absorb heat. That 25% of heat has to go somewhere (relative to a solid rotor). Some of it backs into your calipers and then some of that ends up in your fluid. Get past ~500 degrees, and you get boilded fluid and pedal fade. Put another way, cross drilled rotors may heat your calipers up ~25% faster than solid rotors, resulting in fade before your final lap. So if you got solid rotors, you could go about 25% longer [not exact math, of course]. Similarly, if you put on endurance pads that generate less heat, you could go a little longer. And if you added more cooling, you could go a little longer. And if you put in fluid that can take 600 degrees, even longer. [*note that cross drilled rotors may actually have a better initial "bite" due to increased leading edge contact with the pad*] And none of these things will effect you stopping power, just the way heat is managed by your braking system.

To reduce heat you can do many things:
1) get better tires - your "blah" tires will not allow you to use the torque generated by your braking system properly - pushing too hard on the brake pedal will lock the brakes, and hit ABS. As a result, you need longer braking zones under, which generates more heat.
2) use less brake (meaning shorter but higher application) - ride the brakes less - but as noted in #1, you might need a better tire.
3) changing to an endurance pad (Pagid Yellow) - you've done this, and it will pay big dividends. Just don't let them get below 1/3. After this they start to lose efficiency and transfer more heat to the caliper. Some start to chunk.
4) change fluid to Motul 600 or Castrol SRF - you've done this, and it will really help. Keep in mind that if you do boil the fluid, you can get by for the weekend by continually bleeding BOTH nipples in each caliper before your next session. But you should probably flush the system when you can as one "boil" effectively reduces the boiling temperature of the rest of the fluid.
5) changing to a solid rotor (dimpled or slotted) - this will increase the size of your heat sink.
6) change to a slightly bigger rotor - *maybe* go to 320mm or 325mm, but not much bigger. Unless you plan on changing piston sizes, which basically means new calipers anyway. This will give you more torque AND a bigger heat sink. [*you can balance bias with bigger front rotors by using a less agressive front pad in combination with a more agressive rear pad to end up with the "same" system before you changed rotors (e.g., PFC 97F/ PFC01R or RS29F/RS14R)]
7: add GT2 cooling scoops - mega big, but will probably scrape on speed bumps and driveways.
8) add GT3 cooling ducting - this will probably have the biggest effect on keeping your brakes cool out of the air flow solutions available.
9) you could also change ride height and spring rates to reduce weight transfer, but this is probably not necessary or as helpful on a double duty car.
10) put your car on a diet - take out the carpet, remove sound deadening material, remove mufflers, take out back seats, etc.

If you did upgrade your brakes, you would be getting 3, 4, 5, 6 - which you could do for way less $ and not have to change calipers.

I'm no brake specialty engineer, but I would wager that running with stickier tires, endurance pads, DOT4 fluid, and more cooling will probably fix your braking "issue." Put your car on a diet and you should be golden.

-td

 

The above is only partly true. Some of it is just guesstimation.
I have experienced the same thing and battled this trouble for God knows how long.

Correct items:
Additional cooling in the form of GT3 ducting will help more than a little. Suncoast.

**Your #1 goal right now ought to be high temp fluid + Pagids from Rennstore + GT3 ducting from Suncaost 100%**
Then go from there. I'll bet DD has minimal trouble from then on. I'd bet on it.

If not:
What he may be lacking is THERMAL MASS. No enough rotor and, to a lesser extent, caliper.

 

DDs brakes are regular ol' 996 brakes expected to do GT3 style work. NOT GOOD!

 

Which part(s)? If you have the info, why hide it from the class? I'm interested to know where I'm not telling the truth.

-td

 

What size rotors are on a 99 996 and what are the largest I can put on without changing the calipers? - I will change to slotted.

 

Stock is 318mm for the front. Please let us know if you find a good source for slotted in this size, as there are not a lot of choices.

Check LPI racing, Deman Motorsports and PFC. Currently I run the 2-piece rotor/hat from PFC -which is dimpled instead of slotted. Stoptech makes a 322, 324, 325 etc, but you'll need a spacer kit.

http://www.demanmotorsport.com/
http://www.lpiracing.com/pc/Porsche-...ors-c11039.htm
http://www.vividracing.com/catalog/p...5-p-60667.html

-td

 

Don't forget to add the GT3 brake ducts, $35 and two seconds to install. They have wider vanes to get more controlled air in to the disks.

I run PF01 with PF Rotors, SRF fluid, and SS lines and they are sooooo noisy I usually panic brake to shorten the squeeling at traffic lights. They are magic on the track though with zero fade over long 30 minute runs. I run Hoosiers with a very stiff Moton setup so the car is under a much larger load than stock and they have lasted a year now without any problems

I may give Yellows a try here soon.