996TT Brake DIY - Sorting Fact From Fiction by Mikelly

12 minute read

996TT Brake DIY - Sorting Fact From Fiction

Compliments of Mikelly @ www.renntrack.com

There is a lot of "mis-information" out there about what will and won't work with the 996TT and it would be nice to have all the info in one thread...

For instance:

Front Brake Issues

GT2/3 Calipers - Direct bolt on

GT2/3 Rotors - NOT a direct bolt on.

To be able to use the GT2/3 Rotor, which is a different offset than the AWD Turbo Rotor Hat, you would need to replace your suspension upright (The part the strut and hub/axle and balljoints/Tie rod connect at) would have to be replaced. This is a DIY that could be done, but an alignment would be needed and these suspension uprights are not cheap.

Alternatives for the OEM wheel? Unless you have a custom brake hat made, the only alternative is to run the 997Turbo brake Rotor with the GT2/3 caliper. The 997 Turbo rotor is 350MM and clears the OEM 18inch turbo wheel, as does the OEM GT2/3 caliper.

What about the Performance Friction Option??? Nope. PFC does NOT offer a Turbo offset hat in their popular rotor setup. 

OEM Options for plus sized brake systems...

UMW - Kevin sells the complete 350MM front and rear OEM 997 rotor and the updated 997 Calipers in a kit. This kit is remarkable in several areas. First, all parts are OEM upgrades, so servicing the systems is a non-issue if you want to retain Porsche OEM parts. Second, the caliper redesign is impressive, especially on the 997T Rear caliper, which is slightly larger and has a new center bridge to aid in stopping caliper flex. The front calipers are standard GT2/3 fare, which is superior to other designs and fits under the OEM turbo wheel. Check with UMW for specials and availability, but this kit is truly the "whole" package and you won't save a dime putting it together yourself, trust me, I tried.

Suncoast - Suncoast offers a front package of the 997T front 350MM rotor/gt3 6piston caliper. It's all Porsche OEM and a decent "start" of an upgrade. This kit will clear the OEM turbo wheel. Check with Suncoast for this kit... The price difference between the suncoast kit and the UMW kit doesn't save you anything if you eventually want to upgrade the rears as well. You'll spend more money in the longrun on the rear setup by purchasing it later.

AFTERMARKET Options

BREMBO big kit 355 MM brake kits. These kits are well made, massive calipers with additional bracing to fight caliper flex, and lighter two piece rotors. The issues with these kits revolve around wheel clearance (none of them clear the OEM wheel) and pad choices *(apparently there are few selections in compounds).

Brembo is now making 2 piece rotors for the 996TT in both sizes for OEM apps that do not require their caliper kit.

GIRODISC has started making a nice two piece floating slotted rotor for the 996TT for front and rear!!

Rotora Brake kits can be had in several plus sizes, including two different configurations for calipers, both four and six piston. The same warning as with the Brembo brake kit applies. Be careful of wheel fitment.

Wilwood Brake company supplies some of the largest and most aggressive systems for raceteams world wide, and are used by many popular teams. They will put together a kit to suit your needs. Beware that their calipers are much bigger than the OEM stuff, and wheel clearance will again be an issue.

For rear axle:

Brembo and Girodisc both are making a rear rotor in both oem and 350-355mm sizes.

If you won't care about retaining your emergency brake, you can swap your rear rotors to a two piece design as well, and plus them up. Otherwise your only plus sizing for the are the 997 Turbo rotor, and either using your 996 Caliper with a 12MM spacer and 997Turbo bolts, or going to the $1100 997Turbo calipers along with the 997Turbo rotor. 

Floating Vs. Fixed two piece rotor design:

Our calipers are a "Fixed" calper design. Using a "fixed" rotor, which our OEM rotor is, adds stress to the overall braking system. It also adds more weight to the rotor. By going with a floating rotor, you will reduce weight, and allow for slight deflection in the rotor as the materials expand and contract under constant heating and cooling. The down side to the whole "floating" rotor design is the noise. On a road going car the noise of the rotor floating in the hat can be a tad bitt annoying.

Rotor "ONLY" options:

Coleman Racing ( www.colemanracing.com ), Stock Car Products ( www.stockcarproducts.com ), and a host of other race car fabrication companies will make you a rotor to your specified size. I've dealt with both companies over the years in a previous life making and selling suspension parts for another platform. Both companies support the hobbie/grass roots guys with tight budgets. They can make you a rotor to your specific offset, thickness, size, and type: solid/slotted/drilled - You tell them what you want and they make it!

This is a Coleman Racing rotor made for another Rennlister that eventually sold the setup to me... I've tracked with it with great success and low rotor/pad wear so far. It used an 8inch 12 bolt rotor hat custom made of aluminum. Mine is a fixed rotor design, since I still drive the car on the street. The hats cost about $550 per pair and the rotor replacements are about $350 per pair plus hardware (12 rotor bolts each) and shipping. The rotor I use is directional vein vented and slotted. 

You could certainly get a 330MM stock sized vented rotor made up to replace the OEM 996 Turbo units, keeping the cost down, and run these with the proper pads and brake fluid and have a respectable performer in the brake department.

Pad material choices can impact the life of your rotor. Do your research and talk to those who have experience with various types of pad material. Choosing the wrong pad will shorten the lifespan of your rotor, as the aggressive pad material will eat the rotor quicker. I prefer pagid yellows, and feel that if they're good for a 24 hour of LeMans race, they'll last me quite a while. Porsche uses these pads due to their rotor-friendly nature. Again, good enough for LeMans, Good enough for me!

COOLING THESE BRAKES!!! 

One area the OEM brake system suffers in is boiled fluid. Below is a list of the more common performance fluids and their boiling points.

Brand Wet Dry

Castrol SRF 518°F 590°F 

Motul RBF600 420°F 593°F 

GS610 417°F 610°F

AP-600 410°F 572°F 

Brembo LCF 600 399°F 601°F 

ATE-Super Blue 392°F 536°F 

Valvoline 333°F 513°F 

Castrol LMA 311°F 446°F 

Ford HD 290°F 550°F 

Wilwood 570 284°F 570°F 

PFC-Z rated 284°F 550°F 

AP-550 284°F 550°F 

Most race shops recommends Castrol SRF or Motul RBF600 or Brembo LCF 600 due to their high wet boiling points. All brake fluids absorb moisture, some faster than others (except silicone which is not recommended for anti-lock brake systems). Castrol SRF resists moisture contamination (non-hygroscopic) more than any other fluid tested, therefore change intervals can be greatly extended. This reduces the effective cost over a season of tracking. Many drivers say that they can run the same fluid all year long with only bleeding off the fluid in the calipers for each event. This way a can or two will last all year. Other fluids (hygroscopic type) require additional flushing of the system for each track event to maintain the lowest percentage of moisture and the highest boiling point. For cars over 3000 pounds on high speed road courses every race race engineer I've spoken with recommended brake fluids that do not fall below 400°F wet boiling point. I prefer to bleed my brakes before each weekend and I personally use Motul, due to the cost per bottle. I don't like to open a bottle of brake fluid and then re-use it 30 days later, because I'm concerned about the hygroscopic nature of brake fluid and the amount of moisture in the air. Once you open a container of fluid, it should be used and discarded. Others will argue this, but brake performance is one area I don't mess with... $20 worth of discarded fluid after a bleed is worth it to me... I use it over the course of a weekend and then chuck the unused remains.

Brake cooling goes beyond fluid. You need cool air to duct into the area of the brake/wheel assembly to cool the rotor/caliper/pad/wheel bearings/balljoints... yup, your suspension benefits from cooler air... Next time you have a wheel off, notice the heat shields Porsche designed to help stave off heat soak... Fresh air helps all the way around... 

My DIY brake cooling ducts I originally used... These worked effectively but hung down to low and were dragged on speed bumps or other "stuff" that wasn't flat. I've since replaced that system with the GT3RS race cooling ducts made by Porsche. They also hang a little low, but will perform well and get more air into the wheel housing than the stock 996TT units without the hose/ducting route issues.

Brake lines: A popular "upgrade" on many platforms is braded brake lines. I am not so sure that the OEM porsche brake lines need replacing. When I spoke with a couple of race shops, they adviced that the lines fromt he factory were more than sufficient and many left them alone... I bought some steel braded lines from Pelican Parts with the intention of installing them, but opted out after the several discussions with shops who had success without swapping...

One area you must be aware of is pad wear. Do NOT let your pads drop below 1/4inch of thickness if you track your car. The amount of heat generated when tracking your car is more than the 1/4inch of pad material can protect your piston cups/seals from. 

Tools of the DE trade...

I recommend bleeding your brake system before each event. A motiv pressure bleeder is an excellent "one man" tool to aid in bleeding in a very short period of time. Along with that, I use a catch bottle from CDOC and I bleed the circuit from right rear, inner bleed screw, to right outter bleed screw, then left rear inner to left outter, right front inner bleed screw to right front outter, then left front inner blled screw to left outter. I generally don't pressurize my Motiv beyond 14# and I never use the system to "add" fluid. I simply top it off at the end of the bleed. 

UPDATE as of 1/20/2009:

If you do not want to rear this whole thread, READ THIS FIRST:

There are a number of solutions out there, but most of us have found that you can get by with the OEM brakes as a beginner or intermediate driver if you run Motul or SRF (See the chart above), GT3 RS or GT3 Cup Car cooling ducts, and proper brake pads (Pagid Yellows or Yellow front/Black Rear seem to work best).

If you are intermediate to advanced in your driving, you will notice greater endurance, and more consistancy by going to the larger brake systems available, including those offered by Brembo. But make sure you "need" them, as the rotors and pads are much more expensive.

Attached are some pics of the RS29s that had 15 days on the rears and 9 Days on the fronts. The chipped off pad material is from prying on the pads to push the cups back into the calipers before removing the pad.

Some weight data for those interested:

996TT Original Equipment (Iron Disc)

Front Caliper with Pads: 10.1 lbs

Front 330mm Disc: 23.4 lbs

Rear Caliper with Pads: 7.9 lbs

Rear 330mm Disc: 18.9 lbs

996GT3/997TT Front, 997TT Rear Disc (Iron Disc)

Front Caliper with Pads: 13.1 lbs

Front 350mm Disc: 25.6 lbs

Rear 350mm Disc: 21.9 lbs

996TT/GT2 Factory PCCB

Front Caliper with Pads: 13.1 lbs

Front 350mm PCCB Assembly: 12.0 lbs

Rear Caliper with Pads: 7.6 lbs

Rear 350mm PCCB Assembly: 12.0 lbs

Brembo 380mm 6-piston Monobloc Front GT Kit

Front Caliper with Pads, Bracket: 11.9 lbs

Front 380mm Disc: 19.6 lbs

Brembo 345mm 4-piston Monobloc Rear GT Kit

Rear Caliper with Pads, Bracket: 8.9 lbs

Rear 345mm Disc: 14.2 lbs

Brembo 380mm 4-piston Monobloc Rear GT Kit

Rear Caliper with Pads, Bracket: 9.1 lbs

Rear 380mm Disc: 16.6 lbs. 

These are the part numbersfor the front brake ducts:

996 341 183 90 and 996 341 184 90: 2001 996 GT3 Cup.

996 341 117 90 and 996 341 118 90: 2004 996 GT3 Cup, 996 GT2 MY 2001/2002 and 996 STREET GT3 MY 2002.

996 341 117 92 and 996 341 118 92: 2004 996 STREET GT3RS.

996 341 117 91 and 996 341 118 91: 2003/2004 GT2 and STREET 2004 GT3.

997 341 483 91 and 997 341 484 91: 2005 997 Cup.

997 341 483 92 and 997 341 484 92: 997 STREET GT3