Brembo 2-piece disc, brake fluid, and pad install on GMG Racing’s 991 GT3

GMG Racing 991 GT3 – Brembo Performance Install & Review

GMG Racing, an Official Brembo dealer, is one of the premier high performance and professional racing shops in Southern California who specialize in Porsche track preparation. GMG Racing’s background in professional racing campaigning multi-car efforts in the Pirelli World Challenge series with both Porsche and Audi FIA GT3 platforms. Using this extensive racing experience accumulated over the years, GMG Racing also offers up the same upgrades supplied by their technical partners that they trust on the racetrack.

James Sofronas, owner driver of GMG Racing, also owns a personal 991 GT3 shop car to showcase GMG’s capabilities on and off the track. One such way is by holding track day and driver training specifically for 991 GT3 owners at The Thermal Club raceway which is very demanding on brakes and tires.

GMG Racing 991 GT3 Trackday. Photo Credit : GMG Racing

GMG Racing 991 GT3 Trackday. Photo Credit : GMG Racing

One of the first major upgrades done to the GMG Racing’s 991 “WC-GT3” was improve the braking reliability, longevity, and performance under track use. GMG Racing swapped out the Porsche OE discs, pads and fluid on the 991 GT3 with Brembo 2-piece discs, Race Technologies pads, and Brembo Racing HTC64T fluid.

GMG Racing 991

GMG Racing 991 “WC-GT3”

INGREDIENTS REQUIRED:

  • Porsche 991 GT3
  • GMG Racing
  • Brembo 2-piece front disc assemblies.
  • Brembo 2-piece rear disc assemblies
  • Your choice of front and rear pads although Race Technologies TS20’s were used.
  • 6 bottles of Brembo HTC64T Racing brake fluid.
  • Tarett Engineering brake caliper studs (*optional, supplied by GMG Racing)
GMG Racing 991 GT3.

GMG Racing 991 GT3 in stock form.

BRAKE DISC COMPARISON

While the 991 GT3 has very sophisticated brakes for an OE brake package, there is always more that can be done with certain components to improve overall longevity and performance. The OE Porsche brake discs, pads and fluid are all engineered with comfort, serviceability and cost effectiveness in mind.

Brembo OE co-cast discs

Brembo OE co-cast discs

As the braking system’s primary function is to dissipate heat, Brembo uses purpose-designed discs in order to increase the fade resistance and thermal capacity of the system. These discs are directionally ventilated for enhanced cooling and slotted for better performance and continuously refreshing the pad surface. Brembo 2-piece discs are made up of a proprietary advanced cast-iron alloy which offers an exceptional coefficient of friction and resistance to thermal shock and fatigue.

The same Brembo Racing discs trusted every weekend in professional motorsports are also utilized in the Brembo Performance program (GT, GT-R & club race systems).

The OE 991 GT3 co-cast Brembo discs are sized 380 x 34 mm in the front and weigh 24 lbs, and 380 x 30 mm in the rear weighing at 23.4 lbs. The Brembo Racing Heavy Duty “HD” type V front disc assemblies are 24.5 lbs, and the rear Type III assemblies are 22 lbs. The 991 Turbo discs are substantially heavier than the GT3 discs as the Turbo models are harder on front brakes than the GT3 models. Brembo 2-piece disc assemblies on a 991 GT3 or Turbo will offer a net gain in weight savings.

Brembo Porsche OE discs vs Brembo Performance 2-piece disc assemblies

Brembo Porsche OE discs vs Brembo Performance 2-piece disc assemblies

There are many advantages to replacing the OE discs on a Porsche GT3 or Turbo, some of them are:

  • OEM Integration: Brembo upgrades are designed to work seamlessly with the OE Master, ABS and existing brake systems (Example: Integration with the rear parking brake)
  • Weight Savings: Reducing overall un-sprung weight helps improve vehicle dynamics such as handling, braking, and acceleration.
  • Durability: The Brembo discs for these Porsche disc assemblies come from the Brembo Racing program. These discs feature proprietary metallurgy which is resistant to fatigue, cracking, and are engineered for maximum longevity on the street or track.
  • Different Slot Types: Extensively used in professional motorsports, Brembo type III and type V disc face types can be used to tune or adjust the brakes’ technical characteristics to the chassis or driver.
  • Range: Brembo offers lightweight and heavy duty “HD” disc options to suit the needs of the driver, car model (Turbo or GT3) /setup and environment.
  • Replacements: Brembo replacement rings are comparably priced to OE, and when the Brembo discs are worn, only the outer disc ring and hardware needs to be replaced.
  • Drivability: Brembo 2-piece discs maintain the drivability of the OE brakes by using anti-rattle hardware. Brembo’s specific anti-rattle disc hardware utilizes a spring fastener in order to slightly preload the assembly which eliminates the noise (clattering) generally associated with floating discs.

Brembo OE Porsche disc vs Brembo 380 mm 72 vane racing disc

Brembo McLaren spring

Brembo McLaren spring

NOTE: Brembo’s specific anti-rattle hardware which is commonly used in high performance brake disc assemblies was actually developed in the 1990s. This innovation was initially engineered exclusively for the McLaren F1 supercar which is why the hardware is often nicknamed the “McLaren” spring.

 BRAKE DISC INSTALLATION

GMG technicians Ruben and Sergei (who drives a 997 Turbo himself) used their extensive Porsche know how to install the Brembo 2 piece disc assemblies on the GMG 991 GT3 shop car.

GMG Technicians working on GMG 991 GT3

GMG Technicians working on GMG 991 GT3

 FRONT DISC ASSEMBLIES

The OE front discs were the first to be installed. The Brembo performance 2-piece discs and Race Technologies pads are a direct replacement to the OE units. GMG made sure to push the pistons all the way back in to ensure proper stack width (2 pads and brake rotor total width). The Porsche center lock “lug” was then removed and the Brembo 2-piece disc assembly and pads were then installed. Once the Brembo performance disc assemblies were fitted, the OE Caliper was re-installed using brand new caliper studs. The entire process was done on the front right disc, and then the front left disc.

Porsche 991 GT3 OE front brakes

Porsche 991 GT3 OE front brakes

Porsche centerlock unit

Porsche centerlock unit

Brembo Porsche OE front disc vs Brembo 380 mm racing disc and pads.

Brembo Porsche OE front disc vs Brembo 380 mm racing disc and pads.

The Race Technologies TS20 compound was specified as the baseline pad since the car will be street driven and used on the track. The TS20 offers low noise, dust and good pedal feel. It is also an excellent dual purpose compound for street and light track use.

Brembo 2-piece disc assembly fitted

Brembo 2-piece disc assembly fitted

Brembo 2-piece disc assembly installed

Brembo 2-piece disc assembly installed

Since the GMG Shop car is also their test car, the car will see extended track time on many southern California circuits. A Brembo Type V 380 x 34 mm front disc was specified for the lowest disc and pad wear under heavy track conditions. An optional Race Technologies endurance compound was also supplied for dedicated track use.

  • Brembo Type V (endurance face type): motorsport developed face type with marginally less initial response compared to the type III face type. The Brembo Racing type V face type was also designed to have lower pad and disc wear for certain long distance endurance races (mostly 10, 12 and 24 hour races).

REAR DISC ASSEMBLIES

Once the front disc assemblies were installed, GMG then turned their attention to the rear discs and pads. The exact same installation procedure was followed for the rear disc assemblies as well. The rear right corner was installed first, and then the rear left corner was installed. GMG installed new caliper studs on the rear as well when re-installing the OE Porsche calipers. Race Technologies TS20 compound pads were used for the rears as the baseline pad.

Porsche 991 GT3 rear brakes

Porsche 991 GT3 rear brakes

Porsche OE 991 GT3 rear discs vs Brembo performance Type III discs

Porsche OE 991 GT3 rear discs vs Brembo performance Type III discs

Tarrett Engineering Caliper studs used by GMG Racing.

Tarett Engineering Caliper studs used by GMG Racing.

GMG installed Tarett Engineering caliper studs.

GMG installed Tarett Engineering caliper studs.

RT TS20 rear pads

RT TS20 rear pads

The Brembo Type III 380 x 30 mm rear brake disc was specified for optimum balance and brake release under heavy track conditions. This is because the 991 GT3 shifts its’ brake balance towards the rear under braking. The smooth release characteristics of the Brembo Type III face type can help a driver avoid rear tire in stop lock up while still maintaining optimum braking performance.

  • Brembo Type III (aggressive face type): motorsport developed face type with an emphasis on high initial response while maintaining a smooth pedal release.
Brembo 380 x 30 Type III rear disc fitted.

Brembo 380 x 30 Type III rear disc fitted.

Brembo Performance Type III rear discs installed on GMG 991 GT3

Brembo Performance Type III rear discs installed on GMG 991 GT3

As mentioned earlier in this article, the Brembo 2-piece disc assemblies are compatible with the Porsche factory parking brake. One does not have to compromise and lose the parking brake functionality when installing the Brembo disc assemblies.

BRAKE FLUID AND BLEED

Upgrading brake fluid for spirited, track or racing use is easily one of the most overlooked things when thinking of upgrading any component or part of the brake system. Brembo’s HTC64T brake fluid is the top fluid used in the top professional racing categories around the world (Examples: F1, FIA GT, LMP1). This is because the Brembo fluid offers low compressibility, good after boil recovery, and high boiling points.

  • Brembo HTC64T Typical Applications: Open Wheel*, Stock Car, Rally, Endurance & Sprint GT**, Track Day.

*Brembo HTC64T is one of a very few select fluids being actively used by F1 teams.

**Brembo HTC64T and LCF600 Plus are both racing brake fluids which are actively used and homologated for FIA GT3 & GTE based sports-car racing.

  • Independently proven low Compressibility at severe temperatures.
  • Dry Boiling Point: 335 C (635 F)
  • Racing Use Only
Brembo HTC64T

Brembo HTC64T (used in F1, FIA, GT, LMP1)

Brake fluid performs a very critical function as it is the “life blood” of the brake system, as it is the foundation to hydraulically transfer brake pedal effort to the brake caliper’s pistons. Brake fluid also performs a vital function of lubricating caliper piston seals brake fluid performance (or the lack of) can directly affect brake pedal feel, pressure and consistency through the operating temperature range. It is also one the most cost effective ways to improve brake pedal consistency (avoiding spongy pedal) under high temperature use.

Once the Brembo performance 2-piece disc assemblies and RT pads were installed on all four corners, the OEM brake fluid was flushed and bled with Brembo Racing HTC64T brake fluid. As the fluid was being bled on each corner, GMG made sure to keep an ample amount of new fluid filled in the master cylinder reservoir to ensure that air did not enter into the hydraulic system.

Brembo fluid bleed

Brembo fluid bleed

Brembo HTC64 being poured in

Brembo HTC64 being poured in

ON TRACK IMPRESSIONS

To evaluate the results of the new Brembo discs, fluid bleed, and RT pads, the GMG Team took the 991 GT3 shop car to Thermal Club.

Driver (James Sofronas) and GMG Team comments: Testing out a new setup @thethermalclub today! @jamessofronas had the GMG 991 GT3 out and with the new Brembo Brake pad and Rotor setup says that the car is even more amazing! A predictable pedal feel without activating the ABS too early. A must have for any car that is going to see some track time! Combined with Pirelli Trofeo R tires it is just a winning combo!

Thermal Club Track layout. Image: Thermal Club

Thermal Club Track layout. Image: Thermal Club

Thermal Club located in Palm Springs, California often has very high ambient temperatures which can be demanding on the car, tires, and brakes. The effectiveness of brake cooling is only as good as the temperature of the air flowing thru the brake ducts (if the ambient air is hotter, the brakes will not cool down as much). The track layout and surface can be very similar to some of the European GT tracks, featuring many high speed to low speed braking zones, and a high level of mechanical grip (the more grip you have, the harder you can brake). GMG Racing has setup their shop GT3 understanding the demands of the various tracks around Southern California, and the Porsche 991 GT3, for optimal results.

GMG Racing 991 GT3 and R8 LMS Ultra at Thermal

GMG Racing 991 GT3 and R8 LMS Ultra at Thermal

Modern sports cars have very sophisticated OE ABS systems and engaging the ABS under braking can lead to poor threshold braking, lack of pedal feel, and potentially result in a slower lap time. Having a high overall level of braking confidence and control, usually allows the driver to spend less time on the brake pedal. If the brakes offer enough performance and control for the driver to stay out of ABS engagement (depending on their driving style and car setup), the result is usually a faster lap time on track.

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Brembo Carbon Materials (CCM, CCM-R, and Racing Carbon)

Brembo Carbon Materials (CCM, CCM-R, and racing carbon)

 

Brembo Offers 3 Types of Carbon Based Discs:

  1. Carbon Ceramic (CCM): street use
  2. Carbon Ceramic (CCM-R): street and track use
  3. Carbon-Carbon: race use

Original Equipment Carbon Ceramic Material (CCM):

CCM discs supplied for the OEM are designed to offer significant weight savings over typical cast iron OEM discs while offering outstanding performance and very long life under typical street use. However, OEM CCM discs have limitations for serious performance driving and dedicated track use.

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Carbon ceramic offers significant weight savings over typical cast iron OEM discs

OEM CCM discs do not wear in the same way as cast iron discs. The life on CCM discs is determined by the loss of disc mass as the material oxidizes. This cannot be verified by simply measuring the overall disc thickness like traditional iron discs. Each disc assembly is weighed after assembly and then the minimum allowable weight is permanently etched into the bell. In order to check the weight after use, a cleaning procedure must be performed before checking the weight.

An exhaustive on-road and on-track test program is needed during vehicle development in order to manage airflow to the discs in order to provide enough cooling to achieve satisfactory component life. Oxidation increases rapidly with temperature and it is for this reason that extended high temperature use such as experienced on the race track dramatically reduces the discs life.

OE carbon ceramic (CCM)

OEM carbon ceramic (CCM)

OEM CCM discs are designed to be used with very specific brake pad materials. While there are other pad materials supplied on the market by various pad manufacturers claiming to be “CCM friendly”, there is currently no established validation process for such materials. Pad materials developed for cast iron brake discs will have considerably different results when used on CCM if the various factors are not considered. Pads used with CCM discs also have much greater surface area than would be present in a similar performing cast-iron system which somewhat offsets the weight savings of the disc.

  • Production Process Time: Relatively quick production time (for a carbon-based material), approximately 4 weeks (1 month).

Brembo Racing IndyCar Carbon racing discs & pads

Brembo Racing IndyCar carbon racing discs & pads

Brembo Racing Carbon-Carbon:

Brembo carbon-carbon materials are used in the top levels of professional motorsports in such racing categories as open wheel (i.e. Formula 1 and IndyCar) and sportscar racing (i.e. LeMans and LMP1) amongst others. The latest motorsport carbon-carbon discs offer stable performance over a wide temperature range, are extremely lightweight, and are highly wear resistant.

Brembo F1 carbon-carbon disc

Brembo F1 carbon-carbon disc

While many companies market high performance and racing carbon materials, there are only a few manufacturers who sell carbon-carbon brake materials to the top levels of professional motorsports. These are: Brembo, Carbone Industrie, and Hitco (a subsidiary of the Brembo SGL Group). Brembo supplied over 60% of the Formula 1 field in 2014 and is the sole supplier for IndyCar, Along with supplying brake systems to both factory run Porsche and Audi LMP1 efforts in the FIA WEC (World Endurance Championship) for 2015. It is quite normal for an LMP1 car racing at the 24 hours of LeMans to finish the endurance race without any disc or pad change.

Side profile of a carbon-carbon disc.

Side profile of a carbon-carbon disc.

Racing carbon-carbon systems differ from other brake systems in that they utilize a pad that is also made of carbon-carbon material very similar to the disc material. There are specific carbon-carbon formulations for the disc and pads that can be chosen to suit the system to the needs of the racing series, car, track, or driver.

Wear occurs in a carbon-carbon system both through material thickness reduction, as well as by oxidation. During a braking event, the temperatures reached in a carbon-carbon system can be well in excess of those seen in a racing cast-iron system, but the airflow management must be such that the temperatures are brought down significantly to avoid excessive oxidation. Racing carbon-carbon systems do not work well at low temperatures, and are for motorsports use only.

  • Production Process Time: Approximately 28 weeks (7 months) for production from start to finish.

Brembo CCM-R discs.

Brembo CCM-R discs.

Brembo CCM-R:

Brembo created the CCM-R material by applying the knowledge gained through developing and supplying carbon-based brake materials for both OEM road use and racing applications. Brembo CCM-R discs are sized and cross-drilled similar to the OEM CCM material discs, however, the base material, production process and construction is more in-line with Brembo carbon-carbon racing discs. CCM-R discs were developed with high-performance and racing use in mind.


Debut of CCM-R for the Nissan GT-R (R35)

Brembo CCM-R material comparisons to CCM:

  • Increased material strength, thermal conductivity, and coefficient of friction
  • Reduced temperatures
  • Significant increase in disc life, especially under track conditions
  • Density similar to CCM, but potential for reduced weight due to ability to reduce disc and pad dimensions
  • Wear extent can be determined by visual inspection

CCM-R discs and pads are delivered pre-bedded with a specific friction material for street and track use which will operate in a wide temperature range. If the customer is using the vehicle for primarily track or race use, a race-only material can be specified.

  • Production Process Time: Approximately 28 weeks (7 months) for production from start to finish.
Porsche 997 GT3R Hybrid Equipped with Brembo Racing brakes - ALMS 6 hour endurance race

Porsche 997 GT3R Hybrid Equipped with Brembo Racing brakes – ALMS 6 hour endurance race.

Porsche 997 GT3R Hybrid Equipped with Brembo Racing brakes  - ALMS 6 hour endurance race

Porsche 997 GT3R Hybrid Equipped with Brembo Racing brakes – ALMS 6 hour endurance race


Pre-Bedding:

Pre-bedding is the process of transferring pad material to the disc surface in a controlled environment. It is critical to have a transfer layer of pad material on the CCM-R disc to generate friction. Due to the material strength of CCM-R and the high level of surface hardness, it takes considerable pressure and temperature to transfer pad material onto the disc surface. This is done on a high inertia brake dynamometer using very specific computer controlled programs at the Brembo factory.

Carbon ceramic pads that were used to pre-bed the discs

Carbon ceramic pads that were used to pre-bed the discs

Brembo CCM-R discs pre-bedded and matched to specific friction materials.

Brembo CCM-R discs pre-bedded and matched to specific friction materials.

Representative Component Weights:

  • Brembo 355x32mm, 53mm annulus Cast-Iron 72-vane disc ring: 16.5 lbs
  • Brembo 360x32mm, 64mm annulus CCM-R disc ring: 7.5 lbs
  • Brembo 355x32mm, 53mm annulus Carbon-Carbon disc ring: 5.8 lbs

Typical Pad Weights – For Perspective:

  • Brembo 6-piston 26mm thick Cast-Iron disc race pad: 1.8 lbs
  • Brembo 6-piston 17mm thick CCM-R disc pad: 2.7 lbs
  • Brembo 6-piston 26mm thick Carbon-Carbon race pad: 0.7 lbs
Brembo CCM-R Grain Structure and Brembo Carbon Carbon grain structure

Brembo CCM-R Grain Structure and Brembo Carbon Carbon grain structure

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