Porsches have been known for superior braking performance since the 356 C. The 911 has always had a favorable brake-swept-area to weight ratio and the Factory’s latest automobiles maintain that tradition. The latest street braking systems, the Big Red brakes, are capable of generating 2000 HP of braking! These brakes are larger than any of the 917 or 935 brakes that were used on cars having up to 4 times more power than the Twin-Turbo 993’s.

In the tradition of Porsche, it is possible to upgrade any 911/914-6/930/964/993/996/Boxster to the latest factory braking system or add aftermarket brakes that are even larger. Of course, the limitation is the size of the wheels that you use. To utilize the largest braking systems, you need to use 17" or 18" wheels with the correct offsets to maintain suspension clearance.

Lets talk about the things that you need to consider when deciding to upgrade your Porsche’s braking performance. The first thing to discuss is brake fade. There are two main causes of brake fade:

     2) Pad material failure.

Brake fluid overheats when the calipers and the brake pads transfer excessive heat into the fluid causing it to boil. Boiled brake fluid changes to compressible vapor which causes the spongy pedal you feel with hot brakes. The other type is caused by the overheating of the pad material. The surface of the pad at the rotor contact face turns to a liquid and lowers the coefficient of friction rather drastically. This is caused by using the wrong pad compound for the application, or not bedding the pads properly and experiencing the phenomenon known as "green fade". We will discuss this when we talk about brake pads.

There are several parts of the overall braking system that can be upgraded individually; other components require installation as matched parts.

In this order, you should consider:

Improving  brake cooling should be the first thing you do when deciding to improve your brakes and prevent fade. Installing big brakes will do little good unless you remove the accumulated heat from the rotors and calipers, since adding larger brakes simply builds additional heat into the wheelwells and hub/bearing assemblies. You need to force air through the rotors and out of the fenders before you will be able to take full advantage of the larger brakes. Brake fade from the added heat will eventually overheat the calipers and boil the fluid unless you address this issue first!

There are several brake cooling kits on the market that work quite well. These inexpensive kits utilize brake scoops that force ducted air into the eye of the rotor. Certain front spoiler styles have openings where a creative person could attach cooling hoses that route air  to the brakes. This helps stabilize rotor temperatures and lowers the amount of heat transferred to the pads and calipers. Consequently, the less heat that is transferred to the fluid, the less chance of brake fade caused by boiled brake fluid. This will also help maintain the proper working temperature of the pads. Autocrossers may not need additional brake cooling since that application requires the brake pads to maintain their temperature for best frictional characteristics. The lower speeds in autocrossing does not put same demands on the braking system as track events can.

High-Performance Brake Fluids

The next item to upgrade is brake fluid. No matter what brake fluid you use, you need to change the brake fluid at LEAST every year. We strongly recommend the system is flushed once per year to prevent internal caliper corrosion and remove the old fluid that has absorbed moisture, thus significantly lowering its boiling point. All non-silicone brake fluids are hygroscopic by nature. This means that the fluid will slowly absorb moisture over time and the dissolved water in the fluid boils at 212 deg F, lowering the system’s boiling point drastically. In fact, one to two good hard stops with old fluid can boil the system instantly, causing the pedal to sink to the floor while you are trying to get stopped! Brake fluid is relatively inexpensive so change it once a year. Your calipers and its internal parts will last a lot longer if the fluid is kept clean and dry.

Everyone has their favorite method of flushing or bleeding the brakes. We strongly recommend the pressure bleeding method as the best way to flush the old fluid out and rid the systems of air bubbles without overstroking the Master Cylinder. We use a pressure bleeder that is portable for use at the shop or racetrack. This allows one person to flush the brakes and keep the master cylinder full.

There are several choices for good brake fluid. We have listed the most popular ones and their physical characteristics as related to braking performance. The most relevant number to compare is the wet boiling point. This tells you something about the fluid’s affinity for water. The lower the wet boiling temperature, the more moisture fluid will absorb. True racing-type brake fluids are quite expensive and frankly unnecessary unless you are must use small brakes such as in Historical Racing venues or using carbon-carbon brakes. We list those specifications for comparison only. Rennsport Systems uses and recommends ATE Super Blue or Type 200 (gold) for their performance and cost effectiveness.

Lots of people ask about what DOT 3, DOT 4, and DOT 5 really mean. These are a set of specifications about dry and wet boiling points for each grade of brake fluid. As you will see, this is a guideline only. You must read the specification on the product’s container. All brake fluid should be purchased in small cans, and if not used immediately, discarded. Once the seal on the container is broken, the contents start to absorb moisture.

                                        DOT-3 DOT-4 DOT-5

Now, for comparison, here are the specifications for some of the most popular high-performance brake fluids in use.

     Boiling Points              Dry      Wet

Quite a variation! Before you make any fluid purchases you should know a few things. AP 600 is not compatible with any other fluid. It was formulated for F1 and other cars using carbon-carbon brake components that will see temperatures of over 1000 deg/F. Castrol SRF, another very fine product, will set you back about $ 73 per liter while the Motul and Ate Super Blue brake fluids can be purchased for about $12 per liter or less. This is why we recommend those two products. They will perform quite well when changed on a regular basis. Under certain circumstances of track conditions, vehicle weight, brake swept area, and engine horsepower, one may require the use of a super-duty fluid such as the Castrol SRF. Be sure that you have effective brake cooling before resorting to these measures. You should also be sure that the brake fluid that you decide to use is compatible with what you currently are using. Check with the brake fluid’s manufacturer to be sure!

This is the next item on the agenda for improved brake performance. There are many choices of brake pads from very reputable suppliers to choose from. There are many factors that affect the choice of brake pads that include:

     4) Personal preference

Since each brake pad compound has an optimal temperature operating range, the factors listed above will influence the pad operating temperatures. As an extreme example, the old Ferodo DS11 racing compound didn’t develop much friction until the pads reach close to 450 deg/F . This made them quite unsuitable for the street, or even cars with large brake swept areas that take some effort to reach these temps. On a heavy car or one with solid rotors, these pads worked OK, however there are now excellent performance pads that have good friction characteristics starting as low as 200 deg/F. These items can work just fine on the street as well as the racetrack.

Most performance brake pad manufacturers will provide the working temperatures of their product range and make ballpark recommendation for each application, that are surprisingly accurate.

Performance-racing brake pads come in several compounds including Carbon-Metallic, Carbon-Kevlar, Asbestos-Free and other proprietary combinations. All of these have their strengths and weaknesses such as rotor wear differences, pedal "feel", and friction-temperature linearity.

Unfortunately for your checking account, these ‘magic’ brake pads are not cheap, however the performance gains make them quite cost effective. Until these types of pads became available, owners of early 911’s using "S", SC, and Carrera sized brakes simply had to accept the shortcomings of their car’s braking systems unless they could afford to install Turbo brakes or larger.

Here are some street and racing pads that are currently used:

     1) Porterfield Racing’s R-4 series of Carbon-Kevlar compounds

     2) Hawk Brakes CarboticÒ line of Carbon-Metallic pads

     3) Performance Friction’s complete line-up for many types of applications

     4) Pagid pads; they offer 5 compounds for street and racing. A favorite for Porsches!

     5) Ferodo’s street & racing compounds (Sometimes hard to get)

All of these manufacturers make street and race compounds. Some race pads can be used on the street such as Pagid Orange. Carbon-based performance brake pads do have some drawbacks that some people may not like. All of these pads will make black dust on the wheels to varying degrees and they tend to be noisy. Squeaks, screeches and other odd noises are just part of the package when using these types of pads. Although there is little you can do about the dust besides not using the brakes, noisy brake pads can be effectively quieted down by using an anti-vibration shim on the back of the pads as well as chamfering the leading edges of the pad material. This will make them almost as quiet as street pads.

To prevent the phenomenon known as "green fade", all brake pads must be "bedding in" before you will achieve the maximum friction that your pads are capable of. Green fade occurs when the pad material is overheated before it has a chance to cure. The binders and glues that are used to mold the material together are boiled out and turns to liquid where the pad meets the rotor surface. This is a very scary situation since you get very little warning and the pedal remains firm and high. Bedding the brake pads allows the working surface of the pad to ‘cure’ so that the boiling out process happens in the first few heating cycles. This process occurs continuously through the life of the pad, but the effect is most obvious at first.

Each brake pad manufacturer has their own specific instructions on how to bed their pads properly. When you install new pads, you should gently warm the pad up by making 25 to 30 stops, gradually increasing the brake pressure, but never getting them really hot. This takes bit of practice to perform properly. After making those series of stops, you then make a good hard stop from 110 or so mph, down to about 30 mph and park the car without holding any pressure on the pedal. Let the brakes cool enough that the wheels are cool to the touch. At this time, you should have "cured" the pad material so that it creates its highest coefficient of friction.

Rotors and Calipers

Porsche has used many different combinations and sizes of rotors, calipers, and pads since 1965 on the 911/930/964/993/996/Boxster series of cars. Even the  996 and Boxster's received a new one-piece monobloc caliper from Brembo that is less expensive to manufacture than the current multi-piece caliper.

Porsche has upgraded the rotor and caliper sizes as the weight grew and performance increased.  Rotors from 11.9" to almost 15" have been used and calipers from small two-piston cast iron to massive 4-piston alloy ones have been used on Porsche street and race cars since the sixties. The new 996 GT-2 uses a new ceramic rotor package that is supposed to last for 100K miles. This will be optional on the 996 Twin-Turbo

Porsche rotor sizes didn’t change much between 1969 and 1989. The Carrera 3.2 models had slightly thicker rotors (4mm) than their predecessors. The 78-on 930’s used a derivative of the 917/RSR 4-piston brakes that set the benchmark of performance at that time. Even today, the 930 Turbo brakes are quite desirable for installation on early, light 911’s using 15" wheels. The 964-series began the march to ever increasing brake sizes due to increasing weight and the beginning of the 3.6 litre engines. C4’s from 1989 and C2’s from 1990 to 1994 used larger, thicker rotors than the Carreras. The C2 Turbo cars were the next leap in rotor sizes that are still in use today.

Porsche used cross-drilled rotors with mixed success. The Zimmerman rotors used on the 930 Turbo brakes were very soft and crack prone, even though the holes were chamfered. The later Brembo rotors will also show some wear when used with most performance brake pads. Some of the best rotors in the world are made in Britain by AP and Alcon. Those rotors, when properly adapted, seem to be superior to the Brembo ones in terms of wear and crack resistance. All drilled rotors will crack sooner or later if overheated. Slotted rotors are more durable in this regard however they are heavier. One reason that most large iron rotors are cross-drilled is to save some unsprung weight. Since nice big, light, carbon rotors cost $1000 each, saving some weight without bankruptcy, is important. Plus, carbon rotors possess very little friction until they reach 500-600 degrees F. Porsche's PCCB ceramic matrix rotors while very light, seem to have mixed success when used for   track events.

The first performance brake caliper used on Porsche street cars was the aluminum "S" caliper. Prior to that, various iron calipers were used; particularly the "M" and "L" versions. "S" calipers were used on all 911S cars, early Carreras, and 75-77 930 Turbos; the latter application with poor success. Those cars have too much power and overall weight for such little brakes.

The Carrera 3.2’s used iron calipers in a similar size to the "S" ones. Starting in 1989, the C2/C4 and 993 series were equipped with various sizes of 4 and 2 piston calipers made by Brembo. These were loosely called 928S-4 brakes due to their introduction on that car. Offered in many different versions for 944 Turbo, 928S-4, C2/C4 as well as front and rear versions, these have proven to be the centerpiece of Porsche Brake upgrade kits. Various rotors from Alcon, Brembo and Zimmerman allow these to be fitted to almost any type of 911.

The interchangability of all of these brake components is one of the great features of a 911. In most cases, you can adapt the latest Big Red brakes from the 993 TT to almost any 911 if you use the correct wheels. Of course, you cannot easily adapt the latest Bosch ABS V, however judicious use of the brake pedal will allow full use of these big brakes.

Here are some rough comparisons between all of these Porsche Brake systems. Due to variations between caliper piston sizes, and rotor diameters in each application, it’s very hard to make direct comparisons.

                    Rotor Sizes F/R          Pad area/sq-cm

Again, use this data only for a rough comparison, not for predicting brake performance.  There are far too many variables to make those projections. Suffice to say, that installing any of the 930 / 964 / 993 brakes on an earlier lighter car will be an impressive and worthwhile improvement! There are even larger brakes from Porsche using 380mm rotors that are found on the 993 3.8 RSR and 996 GT-R (RS) racecars.

Master Cylinders

This part of the package is quite easy. Porsche used several sizes of master cylinders from 1969 to the present, ranging from 19mm to 24mm. Brake pedal efforts varied as well from the non-boosted brakes used on the pre-75 cars to the latest hydraulically boosted Twin Turbo ones.

The main reason to update a Porsche equipped with a 19mm master cylinder is when installing any of the 4-piston calipers as used on 930’s and the later C2/C4/993 brakes. You must use a 23mm master cylinder to ensure moving enough fluid per stroke into those large volume calipers. This will prevent the brake pedal from sinking to the floor when actuating these big brakes. The 19mm master cylinder simply doesn’t have the capacity to move enough fluid to move 4-piston calipers.

Porsches that came with high capacity master cylinders are:

     3) All 993-996 25.4mm

     4) All 993-996 Twin-Turbo's 25.4mm

The 89-94 C2/C4's use a 20.6mm master cylinder  If you have excessive brake pedal travel after installing the Big Red TT brakes, its recommended that you use the larger 23.1mm master cylinder from the Turbo.