stout

The "should" seems a logical assumption, BUT the braking system is up to things these days -- like "priming" the pads.

Maybe that's all it's "up to," maybe not.

I think we might be getting off-topic here, though, and am willing to take part of the blame...

pete

Carrera GT

Update your avatar and your signature pic and we'll start talking ... : )

Nothing fancy about a $50 pyro -- I saw a keychain pyro at the race shop at Sears on the weekend -- $30?

Definitely some people are hard on brakes, heavy on the pedal. It's one of the more subtle aspects of "smooth = fast."

It's been a popular tweak to put on Pagid blacks to increase rear bias in the 996 GT3 and RS calipers and blacks on the rear with 993 Big Reds on a Turbo. And that simple technique to increase effective rear bias does a lot, but it's not relevant to what we're seeing in the 997 GT3 -- and again, I'm not calling it as a defect along the lines of the failing rotors and pads of the 996 era "first gen."

03-turbo911

Since the affected cars all appear to be PCCB brake equipped, I don't see TC as the culprit here. I've run all day with no hint of brake fade or soft pedal on a track that is infamous for eating brakes for lunch. Mine's steel by the way.

997gt3north

- my guess, and we may never find out, is that the compound they chose for the pads is too soft - i.e. they didn't want buyers to have to purchase new rotors after 20,000 miles

- and now that they have effectively dialled in more rear bias + pump the pads to get a quicker response, you add a little limerock 65 second laps with huge braking into bigben + 30 seconds later big braking into the Uphil + 10 seconds later above average braking into Westbend and then finally more brakes 10 seconds later into The Downhill + not great stock fluid

and

- then you get brake fad

- then you get lots of heat and above average pad wear on the overworked rars


If I remember one of the first times I took my heavy S4 to the track and I left in street pad sent by stoptech - I can say that besides brake fade I also didn't exactly get good rotor life (basically kille them in a 2 day event)

It looks to be that the pad just weren't made for a heavy braking track - and thus they are great for street dring and help the rotors last 100,000miles

So, who wants to be the first to try some kind of Pagid or other pad on their ceramics (19s, 29s, etc)

JasonAndreas

Normally the proportioning valve hangs off the hydraulic unit but in Porsches with computer controlled front/rear brake bias (EBV) the valve is replaced with the pressure sensor. What someone needs to do is find the "Brake Proportioning Control" line in the 997GT3 Running Gear section of Poses. It will say EBV, Excluded, Without or ~55Bar.

The general brake system description in Poses;

--------------------------------------------

The new 911 GT3 now comes with "Traction Control" (TC), a system that improves driving stability when accelerating.

Just as it is used in the Carrera GT, 911 GT3 Traction Control activates the following systems:


ABS (Anti-lock Brake System)
ABD (Automatic Brake Differential)
ASR (Anti Slip Regulation)
EDTC (Engine Drag Torque Control)
If the drive wheels start to spin, ABD first brakes the individual wheel that is slipping the most. If both wheels are spinning,
ASR is activated and decreases the engine power by overriding the engine control and reducing acceleration and the ignition angle.

EDTC intervenes if the rear wheels start to lock because of the engine drag torque (e.g. when downshifting on a slippery road). In such a situation, EDTC can quickly open the throttle by demanding more power from the engine control, thereby restoring driving stability.

--------------------------------------------

The standard 911 GT3 brake system, with its grey cast iron brake discs, improves on the 911 GT3 (996) brakes. To do this, it includes components from the new 911 Turbo and Carrera GT.

The front brake discs are taken from the 911 GT3 (996), but they are combined with 6-piston brake calipers from the rear axle of the Carrera GT. The brake-caliper pistons are thermally insulated with ceramic insulating inserts. Even under extreme loads, therefore, brake fluid is better protected against overheating. New brake-air spoilers and air-deflecting blades also ensure optimal brake cooling.

The complete brake system, including brake ventilation, is fitted to the rear axle of the new 911 GT3. The diameter of the brake disc has been enlarged to 13.8 in. (350 mm) to further increase brake performance, as have the pad areas and piston diameter.

The 911 GT3 is fitted with a 9-inch tandem brake booster, as on the current 911 Carrera 4 models and the new 911 Turbo. However, the brake force ratio (i=3.5) has been tuned specially for the 911 GT3.

frayed

On a sidenote, EDTC is marketed as a system intervening just as you have stated. Will it intervene in an oversteer throttle lift situation? To me it would seem

JasonAndreas

Here is the rest of the technical data for the brakes from Poses, unfortunately the proportioning info is located somewhere else.



WM 4600TW Technical data/Brake wear limit
Technical values
Location Description Type Basic value Tolerance 1 Tolerance 2
Brake booster (vacuum) All (Turbo, GT3/GT3 RS) Tandem/diameter 9 inches
Brake booster transmission ratio (i) Turbo Factor 5.5
Brake booster transmission ratio (i) GT3/GT3 RS Factor 3.5
Diameter of brake master cylinder, front/rear All Diameter 26.99/26.99 mm
Brake master cylinder stroke, front/rear All Dimension 20.5/15.5 mm
Brake disc diameter, front Diameter 350 mm
Brake disc diameter, rear Diameter 350 mm
Effective brake disc diameter, front Diameter 284 mm
Effective brake disc diameter, rear Diameter 292 mm
Piston diameter in six-piston brake calliper, front All Diameter 2 x 38 mm
Piston diameter in six-piston brake calliper, front All Diameter 2 x 32 mm
Piston diameter in six-piston brake calliper, front All Diameter 2 x 28 mm
Piston diameter in four-piston brake calliper, rear All Diameter 4 x 34 mm
Effective brake pad area, front Area 448 cm²
Effective brake pad area, rear Area 248 cm²
Total brake pad area Area 696 cm²
Pad thickness, front Measured value approx. 12.0 mm
Pad thickness, front (wear limit) Measured value 2 mm
Pad thickness, rear Measured value approx. 12.0 mm
Pad thickness, rear (wear limit) Measured value 2 mm
Brake disc thickness, new (front) Measured value 34 mm
Brake disc thickness, new (rear) Measured value 28 mm
Minimum brake disc thickness after machining, front Brake disc can only be reworked symmetrically, i.e. equally from both sides! Measured value 32.6 mm
Minimum brake disc thickness after machining, rear Brake disc can only be reworked symmetrically, i.e. equally from both sides! Measured value 26.6 mm
Brake disc wear limit, front Measured value 32.0 mm
Brake disc wear limit, rear Measured value 26.0 mm
Peak-to-valley surface roughness of brake disc after machining (max.) Measured value 0.006 mm
Thickness tolerance of brake discs (max.) Measured value 0.02 mm
Lateral runout of brake disc (max.) Measured value 0.03 mm
Lateral runout of wheel hub (max.) Measured value 0.03 mm
Lateral runout of brake disc when installed (max.) Measured value 0.06 mm
Pushrod play Measured at brake pedal plate Measured value approx. 1 mm
Diameter of parking-brake drum Parking brake/hand brake (drum brake acting mechanically on both rear wheels) Diameter 180 mm
Diameter of parking-brake drum, wear limit Diameter 181 mm
Width of parking-brake shoe Measured value 25 mm
Thickness of parking-brake pad Measured value 4.5 mm
Thickness of parking-brake pad, wear limit Measured value 2 mm
Brake booster diameter (vacuum) All (Turbo, GT3/GT3 RS) Tandem/diameter 9 inches
Brake booster transmission ratio (i) Turbo Factor 5.5
Brake booster transmission ratio (i) GT3/GT3 RS Factor 3.5
Diameter of brake master cylinder, front/rear All Diameter 26.99/26.99 mm
Brake master cylinder stroke, front/rear All Dimension 20.5/15.5 mm
Brake disc diameter, front Diameter 380 mm
Brake disc diameter, rear Diameter 350 mm
Effective brake disc diameter, front Diameter 315.8 mm
Effective brake disc diameter, rear Diameter 292 mm
Piston diameter in six-piston brake calliper, front Turbo Diameter 2 x 36 mm
Piston diameter in six-piston brake calliper, front Turbo Diameter 2 x 32 mm
Piston diameter in six-piston brake calliper, front Turbo Diameter 2 x 28 mm
Piston diameter in six-piston brake calliper, front GT3/GT3 RS Diameter 2 x 34 mm
Piston diameter in six-piston brake calliper, front GT3/GT3 RS Diameter 2 x 30 mm
Piston diameter in six-piston brake calliper, front GT3/GT3 RS Diameter 2 x 28 mm
Piston diameter in four-piston brake calliper, rear All Diameter 4 x 34 mm
Effective brake pad area, front Area 448 cm²
Effective brake pad area, rear Area 248 cm²
Total brake pad area Area 696 cm²
Pad thickness, front Measured value approx. 12.0 mm
Pad thickness, front (wear limit) Measured value 2 mm
Pad thickness, rear Measured value approx. 12.0 mm
Pad thickness, rear (wear limit) Measured value 2 mm
Brake disc thickness, new (front) Measured value 34 mm
Brake disc thickness, new (rear) Measured value 28 mm
Brake disc wear limit, front Minimum brake disc thickness (wear limit) is stamped on the brake-disc chamber. Example: Min. Th. 33.7 mm Measured value mm (Read value on brake-disc chamber) X.XX
Brake disc wear limit, rear Minimum brake disc thickness (wear limit) is stamped on the brake-disc chamber. Example: Min. Th. 27.7 mm Measured value mm (Read value on brake-disc chamber) X.XX
Wear limit: Surface changes in front and rear brake discs Wear limit: Connected surface fracture > 1 cm² and/or surface roughness of brake disc > 80 micrometer. Replace PCCB brake discs on each axle. Surface changes Values and procedure for: checking front 46 51 02 PCCB brake discs/checking rear 46 54 02 PCCB brake discs.
Thickness tolerance of brake discs (max.) Measured value 0.02 mm
Lateral runout of brake disc (max.) Measured value 0.03 mm
Lateral runout of wheel hub (max.) Measured value 0.03 mm
Lateral runout of brake disc when installed (max.) Measured value 0.06 mm
Pushrod play Measured at brake pedal plate Measured value approx. 1 mm
Diameter of parking-brake drum Parking brake/hand brake (drum brake acting mechanically on both rear wheels) Diameter 180 mm
Diameter of parking-brake drum, wear limit Diameter 181 mm
Width of parking-brake shoe Measured value 25 mm
Thickness of parking-brake pad Measured value 4.5 mm
Thickness of parking-brake pad, wear limit Measured value 2 mm

Technical data - 911 Turbo/GT3/GT3 RS
Operating brake (foot brake):
Dual-circuit brake system with brake-circuit division per axle.
Internally ventilated and perforated grey cast iron brake discs on front and rear axle.
Six-piston monobloc calliper on front axle and four-piston calliper on rear axle.
The brake callipers are painted red for visual differentiation.
Porsche Stability Management (PSM 8.0) on the 911 Turbo (as standard).
Traction Control (TC) on the 911 GT3/911 GT3 RS (as standard).
Location Description Type Basic value Tolerance 1 Tolerance 2
Brake booster (vacuum) All (Turbo, GT3/GT3 RS) Tandem/diameter 9 inches
Brake booster transmission ratio (i) Turbo Factor 5.5
Brake booster transmission ratio (i) GT3/GT3 RS Factor 3.5
Diameter of brake master cylinder, front/rear All Diameter 26.99/26.99 mm
Brake master cylinder stroke, front/rear All Dimension 20.5/15.5 mm
Brake disc diameter, front Diameter 350 mm
Brake disc diameter, rear Diameter 350 mm
Effective brake disc diameter, front Diameter 284 mm
Effective brake disc diameter, rear Diameter 292 mm
Piston diameter in six-piston brake calliper, front All Diameter 2 x 38 mm
Piston diameter in six-piston brake calliper, front All Diameter 2 x 32 mm
Piston diameter in six-piston brake calliper, front All Diameter 2 x 28 mm
Piston diameter in four-piston brake calliper, rear All Diameter 4 x 34 mm
Effective brake pad area, front Area 448 cm²
Effective brake pad area, rear Area 248 cm²
Total brake pad area Area 696 cm²

Test values/wear limits - 911 Turbo/GT3/GT3 RS
Note

Depending on the wear of cast iron brake discs, two condition criteria can make replacement necessary:
Cracking in the holed (perforated) brake disc friction plates is in an advanced state.
Minimum brake disc thickness is not retained due to wear (material erosion due to friction).

Location Description Type Basic value Tolerance 1 Tolerance 2
Pad thickness, front Measured value approx. 12.0 mm
Pad thickness, front (wear limit) Measured value 2 mm
Pad thickness, rear Measured value approx. 12.0 mm
Pad thickness, rear (wear limit) Measured value 2 mm
Brake disc thickness, new (front) Measured value 34 mm
Brake disc thickness, new (rear) Measured value 28 mm
Minimum brake disc thickness after machining, front Brake disc can only be reworked symmetrically, i.e. equally from both sides! Measured value 32.6 mm
Minimum brake disc thickness after machining, rear Brake disc can only be reworked symmetrically, i.e. equally from both sides! Measured value 26.6 mm
Brake disc wear limit, front Measured value 32.0 mm
Brake disc wear limit, rear Measured value 26.0 mm
Peak-to-valley surface roughness of brake disc after machining (max.) Measured value 0.006 mm
Thickness tolerance of brake discs (max.) Measured value 0.02 mm
Lateral runout of brake disc (max.) Measured value 0.03 mm
Lateral runout of wheel hub (max.) Measured value 0.03 mm
Lateral runout of brake disc when installed (max.) Measured value 0.06 mm
Pushrod play Measured at brake pedal plate Measured value approx. 1 mm
Diameter of parking-brake drum Parking brake/hand brake (drum brake acting mechanically on both rear wheels) Diameter 180 mm
Diameter of parking-brake drum, wear limit Diameter 181 mm
Width of parking-brake shoe Measured value 25 mm
Thickness of parking-brake pad Measured value 4.5 mm
Thickness of parking-brake pad, wear limit Measured value 2 mm

Information on machining cast-iron brake discs
Possible complaints
Damage due to lack of use (rusting). This causes vibrations in the steering wheel, noises and brake pedal pulsation.
Brake disc becomes distorted as a result of serious driving, e.g. on a racing circuit.
Too much lateral runout when new brake discs are fitted on dirty or distorted wheel hubs.
Procedure
Check brake disc for cracks, minimum thickness, lateral runout, thickness tolerance, flatness and surface roughness.
If necessary, (depending on the actual brake disc thickness and the brake disc wear limit) machine the brake disc using one of the disc brake dressing machines approved by Porsche. For a list of recommended disc brake dressing machines, see Workshop Equipment Manual, Chapter 3.4.
The brake disc must only be reworked symmetrically, i.e. equally from both sides! Observe the operating instructions for the disc brake dressing machine!
Technical data for 911 Turbo/GT3/GT3 RS - PCCB brakes (option)
Operating brake (foot brake):
Dual-circuit brake system with brake-circuit division per axle.
Internally ventilated and perforated PCCB brake discs on front and rear axle.
Six-piston monobloc calliper on front axle and four-piston calliper on rear axle.
The brake callipers are painted yellow for visual differentiation.
Porsche Stability Management (PSM 8.0) on the 911 Turbo (as standard).
Traction Control (TC) on the 911 GT3/911 GT3 RS (as standard).
Location Description Type Basic value Tolerance 1 Tolerance 2
Brake booster diameter (vacuum) All (Turbo, GT3/GT3 RS) Tandem/diameter 9 inches
Brake booster transmission ratio (i) Turbo Factor 5.5
Brake booster transmission ratio (i) GT3/GT3 RS Factor 3.5
Diameter of brake master cylinder, front/rear All Diameter 26.99/26.99 mm
Brake master cylinder stroke, front/rear All Dimension 20.5/15.5 mm
Brake disc diameter, front Diameter 380 mm
Brake disc diameter, rear Diameter 350 mm
Effective brake disc diameter, front Diameter 315.8 mm
Effective brake disc diameter, rear Diameter 292 mm
Piston diameter in six-piston brake calliper, front Turbo Diameter 2 x 36 mm
Piston diameter in six-piston brake calliper, front Turbo Diameter 2 x 32 mm
Piston diameter in six-piston brake calliper, front Turbo Diameter 2 x 28 mm
Piston diameter in six-piston brake calliper, front GT3/GT3 RS Diameter 2 x 34 mm
Piston diameter in six-piston brake calliper, front GT3/GT3 RS Diameter 2 x 30 mm
Piston diameter in six-piston brake calliper, front GT3/GT3 RS Diameter 2 x 28 mm
Piston diameter in four-piston brake calliper, rear All Diameter 4 x 34 mm
Effective brake pad area, front Area 448 cm²
Effective brake pad area, rear Area 248 cm²
Total brake pad area Area 696 cm²

Test values/wear limits for 911 Turbo/GT3/GT3 RS - PCCB brakes (option)
Note

The following condition criteria can make replacement necessary depending on the wear of the PCCB brake discs:
Surface changes in the brake disc friction surfaces at an advanced stage.
Minimum brake disc thickness is not retained due to wear (material erosion due to friction).

Location Description Type Basic value Tolerance 1 Tolerance 2
Pad thickness, front Measured value approx. 12.0 mm
Pad thickness, front (wear limit) Measured value 2 mm
Pad thickness, rear Measured value approx. 12.0 mm
Pad thickness, rear (wear limit) Measured value 2 mm
Brake disc thickness, new (front) Measured value 34 mm
Brake disc thickness, new (rear) Measured value 28 mm
Brake disc wear limit, front Minimum brake disc thickness (wear limit) is stamped on the brake-disc chamber. Example: Min. Th. 33.7 mm Measured value mm (Read value on brake-disc chamber) X.XX
Brake disc wear limit, rear Minimum brake disc thickness (wear limit) is stamped on the brake-disc chamber. Example: Min. Th. 27.7 mm Measured value mm (Read value on brake-disc chamber) X.XX
Wear limit: Surface changes in front and rear brake discs Wear limit: Connected surface fracture > 1 cm² and/or surface roughness of brake disc > 80 micrometer. Replace PCCB brake discs on each axle. Surface changes Values and procedure for: checking front 46 51 02 PCCB brake discs/checking rear 46 54 02 PCCB brake discs.
Thickness tolerance of brake discs (max.) Measured value 0.02 mm
Lateral runout of brake disc (max.) Measured value 0.03 mm
Lateral runout of wheel hub (max.) Measured value 0.03 mm
Lateral runout of brake disc when installed (max.) Measured value 0.06 mm
Pushrod play Measured at brake pedal plate Measured value approx. 1 mm
Diameter of parking-brake drum Parking brake/hand brake (drum brake acting mechanically on both rear wheels) Diameter 180 mm
Diameter of parking-brake drum, wear limit Diameter 181 mm
Width of parking-brake shoe Measured value 25 mm
Thickness of parking-brake pad Measured value 4.5 mm
Thickness of parking-brake pad, wear limit Measured value 2 mm