jstephanus

Just wondering what people have used successfully for upgrading the brakes on a 996tt that have been otherwise tuned. I am using 18" rims.

Regards,

John

cobra06

The stock TT brakes are 2000 H.P. brakes, probably one of the best stock brake systems in the world. Why do you feel you need to upgrade?

msindi

I agree with Cobra (Cobra: did you get my PM??).
I am debating whether to do the Brembo 8-piston systme for looks but it is a lot of money and the stock brakes are just fine.

Jack

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by cjv:
<strong> I believe the GT3 even has small tire contact tread than the 996tt?
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Actually, as compared to the stock Turbo, the new GT3 has a bit more rubber up front (235x40) and the same size tire on the rear (290x30). <img border="0" title="" alt="[Wink]" src="wink.gif" />

<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />

cobra06

Do you really feel that Porsche, using a 2000 H.P. brake system, that does fanatical breaking trials put an inadequate system on these cars?. I have a fair amount of track time with my TT and yet to have a problem with the system. Whats your basis for inadequate braking outside of comparing the current with another Porsche?.

Jack

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by cjv:
<strong>Jack,

Do you mean 295/30 in the rear or is it really 290/30?
<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Chad: Sorry, my bad, I did mean to type 295x30.
As for the standard GT3 brakes, they are, in fact, bigger than the stock Turbo.

KPV

Here is some engineering food for thought, or lunch <img border="0" title="" alt="[Wink]" src="wink.gif" />

In a static situation (similar to a dynamic situation), the friction force on a surface is determined by only two parameters, the "Coefficient of Friction" and the "Normal Force".

The coefficient of friction is a constant value (usually less than 1) that correlates the relative cohesiveness of two different materials. Some example values of the coefficient of friction are as follows:
Concrete to concrete = 0.8
Clean steel to clean steel = 0.25
Multinomer plastic (Smooth) to Concrete = 0.4
In the case of rubber on pavement the coefficient of friction will likely be around 0.8 to 1.0. This is just a guess.

The "Normal Force" is simply the force on the contact patch acting perpendicular to the surface. So, if the car is sitting stationary on level ground, the normal force would simply be the weight of the vehicle at the particular wheel in question. On a hill, it is a fraction of the weight due to geometry (remember.....perpendicular to the surface). Obviously these weights (forces) change when the vehicle is in motion due to redistibution of loads from accelerating, deccelerating and corning so it is not a simple matter.

Anyway, the Friction equation is Ff=uf x N.

The friction force is NOT brakes on rotors!! I am referring to tires on pavement. Now, bear in mind, the friction force is called upon to accelerate, deccelerate (brake) and change direction (turn). There are only two factors that come into play with regard to friction force, the coefficient of friction and the normal force. So, bottom line, to get more friction force (grip for acceleration, braking or better lateral grip), you have to either change the material (stickier tires) or add weight to the wheels.
Again, just my $0.02.

M Danger

FYI theres a pair of GT2/gt3r calipers on EBay right now

Konstantin

the Gt3R use other brakes and not the same as the Gt2.
for this money you can get my calipers and you get the rears for free;-)
The brakes on the Gt3 are just ok for sport street driving (on the Autobahn)
on the track are not enough if you brake hard.
here the result:
<a href="http://www.968turbo.de/GT3total.htm" target="_blank">http://www.968turbo.de/GT3total.htm</a>
if you upgrade to the Gt3 cup cooling ducts it is ok. if you even go to the Gt2/Gt3Cup 2002 brakes is even better.
What the 996TT really needs is the Gt2 six piston calipers and better cooling. The 355 mm rotors are ok for this car. you need the 380 mm rotors ONLY if you race long endurance races.

Konstantin
PS if you think your brakes are good enough then they are good enough.
PS the bigest advandage with bigger brakes is the better cooling and avoid overheating problems and NOT the better brake performance.
PS3 the Gt3 cup brakes are about 10% better than the street Gt3. ( both with cold brakes)
if the brakes are hot the diference is almost 30%
If the brakes are really hot then......... see the pic on the link I posted before :-(

HBdirtbag

Konstantine just brought up an issue i've been wondering. Why aren't people just swapping on the GT2 six pots? Won't they work w/ the rotors already on the car. And what it seems like alot of people forget is that heating is SOOO important w/ brakes. You need to keep them cool or else they will cook.

now another question, can you install a brake fluid cooler similiar to a tranny cooler to help keep temps down on the track? would it make it too cool for street driving? I know you have to give and take.

Oak

The GT2/GT3 Cup 6 piston calipers and rotors will not just bolt up to the turbo carriers. By Design was able to locate new aluminum carrier castings to accommodate the 6 piston calipers for the FWD of the turbo. From what I understand these carriers are rare and difficult to locate, not sure why? If I remember correctly the new carriers weighed less than the stock carriers, so the unsprung weight was a moot point. The 6 piston calipers are extremely light, virtually the same weight as stock.

From what I've been told the rears calipers are from Porsche Motorsports and the internal pistons are larger.

The GT2/GT3 Cups rotors are 350mm which weigh a few pounds more than the stock 330mm turbo rotors. With the lighter carriers and slightly heavier rotors, I had no noticeable difference in unsprung weight.

Most notable increase in performance was the initial bite and the torque leverage, and modulating, also have not had any issues with brake fading.

On a side note, I have been using the P90 pads which are awsome with the steel rotors. These were formulated for the PCCB rotors, but seem to be working well with steel rotors. Easy on the rotors.
<img src="http://gallery.rennlist.com/albums/Brakes-and-Suspension-Mods/101_0126.sized.jpg" alt=" - " />
<img src="http://gallery.rennlist.com/albums/Brakes-and-Suspension-Mods/GT2_rear_calipers.sized.jpg" alt=" - " />

Konstantin

just add a cooling kit (brake ducts) and that`s it. It is more than enough cooling there and works in street AND track. This is also the only difference between the cup and the street Gt3 front bumber

You can fit the Gt2 brakes even on a stock 996 NA very easily. You just need the front " steering knucles" from the Gt3 cup. After that it is almost bolt on.

Konstantin

T2

What about unsprung weight reduction - that is one primary reason I upgraded to the PCCB's. The car is a different beast with the PCCB's. T2

Joe@Fabspeed

Automakers put biiger more efficient braking systems on cars for many reasons. Porsche uses bigger more capable braking systems based on the weight and usuage of the vehicle. If you have a 996TT streetcar that never ever goes to the racetrack youll never ever need bigger brakes even on the Autobahn. If youre a casual drivers ed user with 8-10 laps sessions on street tires you will still be okay with just a pad change.

Perhaps Cort Wagner or a Supercup pro might like (but not require) bigger brakes.

If you are in a racing situation big braking systems act as massive heat dispersion systems (giant rotors) and big rotors and big pads will give you more capacity and time between replacing rotors or pads.........which in an endurance race is important. In a perfect world in which money was no object and FIA rules/Grand AM didnt object Porsche and others would use the smallest lightest weight carbon carbon brakes they could get away with and then just replace for the next competition.......just like the F1 boys.

Of course for DE, streetdriving, clubracing.......bigger brakes that look like they came off a Boeing 747.....look cool and last long..... so often when pads/rotors and other stuff is shot......they get installed all the time.

Konstantin

we change pads AND rotors twice a weekend on the supercup cars (but only on the fast drivers)
Now you know a secret why our driver won the championship last year;-)
a new pad and rotor has a better "feeling" and make about 0,1 sec pro lap. I doubt a normal Porsche supercup driver will notice this. The same for the average racer and of course for the common street driver .

PCCB are lighter feel better but have an advandage only if you are braking very hard and the normal steel rotors and pads get very hot.
For every day use they brake as good as the steel rotors.

Konstantin