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The article in the link below is designed as a roadmap for upgrading the brakes on a modern Porsche 911, based on the environment and manner in which the car is being driven. The primary focus is on the 911 T trim level, as it and the Base 911 come from the factory with the smallest and most primitive brake package Porsche offers. As such, the brakes on Carrera T have the greatest room for improvement. Everything in this article is also applicable to the other 911 trim levels, but the comparative weights and capabilities will be slightly different vs. the stock brake components on those trim levels. The article is loaded with lots of great tech info, comparative weights and measurements, and many of the considerations we all face when using our Porsches on the road and track.
We've helped thousands of Porsche owners with their brakes, and the info in this article is drawn from our experience providing solutions for each of their unique situations. I hope you find it useful, and thanks for reading!

Complete article here: Porsche 911 Brake Upgrade Guide


Below are a few snippets from the article:

Overview of how an HPDE impacts your brake choice:

HPDE (High Performance Drivers Education) / Track Day / Time Trial / Time Attack

At a track day, you will always put more heat into your brake system than you ever will on the street or at an autoX. Please reread that sentence! Track Days are really the first venue mentioned thus far where battling heat becomes paramount for having an effective and reliable brake system. HPDEs typically have a diverse mix of vehicles being run, a wide range of speeds achieved, and vastly differing driver ability across run groups. As such, it's difficult to recommend a single blanket brake solution for a given vehicle driven at an HPDE. We will therefore preface the next portion of our brake recommendations with a brief look at some of the variables encountered at an HPDE or time trial.

After countless discussions with customers on this topic over many years, we believe there are a few critical considerations when upgrading your brakes for a Track Day or Time Attack. These factors will determine just how much thermal capacity your brakes will require:

Track layout

Tire choice

Vehicle modifications

Driving style and experience

A careful examination of these factors in your personal situation will help guide you towards the most appropriate brake solution. Keep in mind that all these factors are related and cannot be considered in isolation from one another.

Track layout

During a brake event, the rotational energy of the spinning discs is converted into heat and spread throughout your discs, pads, caliper pistons, caliper body, and brake fluid (as well as the surrounding suspension components via radiation). The faster the discs are spinning at the initiation of a brake event, the greater the amount of energy converted, and the greater the amount of heat that needs to be dealt with. Therefore, a track with long straights followed by tight turns generates the greatest amount of brake-related heat. The higher your terminal speed at the end of the straight, and the longer you are on the brakes to slow for a turn, the more heat you’ll be pouring into your brake components. When facing a series of long straights followed by tight turns, the issue is compounded even further. The temperature rise on your brake components is both dramatic and rapid during each intense brake event; then the components are immediately doused with cooling air during the subsequent lengthy straight. These rapid temperature swings are what cause the most stress-related brake issues, not necessarily the absolute temperature the brakes reach.

The distance between stops also dictates how much heat is retained in your brakes. If a track layout has a steady succession of medium straights and tight turns (think Carolina Motorsports Park), your brakes might not reach the same max temperature as they would on a track with longer straights, but they won't have much time to cool between stops, creating heat soak. Flowing tracks with long sweepers are much easier on brakes (i.e. Willow Springs or Roebling Road).As noted above, tracks with very long straights followed by tight turns are the most devastating to your brakes (Watkins Glen, Road America, Circuit of the Americas). A close look at the track(s) you'll be regularly driving will help determine just how much stress your brakes will need to endure, how much thermal mass you should seek in your brake discs, and how much fade resistance your pads and fluid will require.

Tire choice

Brakes don’t stop your car, your tires do. Brakes convert the kinetic energy of the spinning discs into heat, but the tires generate friction with the track surface and actually slow the car. Tire choice has a large impact on how much brake your car can leverage, and how much heat will be generated by your brakes. The stickier the tire, the more brake you can leverage, the shorter your stopping distances will be, and the more brake heat you will generate. More grip = more heat. If you're running low grip all-season tires, or if it rains at an event, your tires won't be able to generate as much friction with the track surface, and you therefore won't tax your brakes as much.

Vehicle mass and horsepower

All else held equal, more massive, more powerful cars place a greater strain on their brake system. A Corvette ZR1 will generally require a much larger pad and rotor as a heat sink vs. a Miata. That is partly because of the mass, and partly because of the horsepower. What may surprise you, however, is that the speed component has more impact on your brake requirements than mass does. Higher speeds increase brake demands at an exponential rate, while adding mass increases brake demands at a more linear rate. If you strip 200lbs. out of your car (easier to accelerate), have a quality coilover system (higher cornering speeds), and add 40hp (greater acceleration out of turns), you may be placing less demand on your brakes in terms of vehicle mass, but you'll need to slow the car from higher speeds when entering brake zones. While it may be counterintuitive, the car might be tougher on your brakes despite its reduced weight (Again, outside the scope of this article, but to learn more on this topic, please research the formula K.E. = 1/2 m v2). Again, the relevant point to this discussion is that more massive, more powerful vehicles require larger, more durable brake components, and anything you do to your vehicle to alter its power output or weight will impact your brake requirements.

Driver experience

If you've never driven anywhere but the street, your first couple of trips to the track will most likely not tax your brake system too heavily, right? Not exactly. You being a complete track newb won't necessarily protect your stock brakes from total destruction. Novice drivers may be easier on the brakes for several reasons: Their corner exit speeds are lower, their terminal speeds entering brake zones are therefore lower, and there's less kinetic energy being transferred into heat during a given stop. That said, novice track drivers also tend to stab wildly at the brakes, stay on the brakes far too long, oscillate between on and off brake, and inflict all sorts of brake abuse a pro driver would never do! The result can be some serious brake punishment. It's therefore impossible to make a blanket statement that a novice driver will be fine on stock brake pads. Reality has proven that statement false countless times, particularly on the faster, heavier cars our customers often take to track days.

So where do these factors leave us when upgrading our brakes for a Track Days, HPDE, or Time Trial? The critical point is, every modification you make to your car and the nut behind the wheel will change the demands on your brake system, and you must adjust accordingly. Just because you successfully used a certain pad compound before, doesn't mean it will work again after you've installed bigger turbos and Hoosiers. Chances are that after your 25th HPDE, you'll be taxing your brakes in a different manner than you did during your first event. You'll be hitting higher speeds, entering and exiting corners faster and on a different line, and your car will likely have more grip and power than it did when you started (you'll also likely be much poorer, but happier!). If you typically run Limerock Park (a short track without many big braking zones) but decide to make a trip to Road America (a crazy fast track with huge brake demands), you need to reconsider how your brakes will be taxed. You must constantly evaluate the overall capabilities of your brake system, and not be afraid to try new brake setups as both you and your car evolve.

Finally, if you want to play it safe and not risk damage to the major components of your brake system, don't EVER drive an OEM brake pad on a road course. It may be more convenient and seem economical to run stock pads, but it will eventually cost you time and money in the long run. There's also not much worse than wasted track time. When you're sitting in the pits watching your buddy rip down the front straight, and your stock pads are a steaming pile of dust stuck to the inside of your wheels, you'll be wishing you spent a couple hundred bucks and took the hour on Friday night to change your pads and bleed your brake fluid! Please read this article on the Essex Blog for even more reasons not to run your OEM pads on the track: “Can I Run my OEM Brake Pads on the Track?”

Now that we have a better understanding of how taking our car to the track impacts our brake system, let’s look at track-specific brake upgrades for the Carrera T:

2-piece Discs

Two-piece Brake Discs- Unsprung weight is the devil to the avid autocrosser. You should always be looking to maximize weight reduction within the boundaries of the rules (or outside those boundaries if you’re clever at it!). Weight reduction in the wheels/brakes/suspension area is particularly beneficial to all aspects of acceleration, turning, and braking, which is the core of autoX. Two-piece discs can in some cases offer substantial weight savings. Aftermarket two-piece discs will have aluminum hats that are lighter than the stock iron pieces, and their overall construction and vane design may offer further weight savings. Since you probably won’t be burning your discs up at a rapid rate, the initial cost of a two-piece disc may be worth the weight loss (commonly $600-$1800 per pair). Just make sure to check the price of replacement iron before committing, since you will eventually need to change the discs which are wear items. Also, keep the size and mass of the discs in mind. A larger-than-stock 2-piece disc may weigh more than the OEM units, which is even more likely on the Carrera T since the OEM discs are so tiny.

AP Racing 2-piece J Hook Discs bring numerous benefits to the table that are especially valuable on the racetrack. Taking your discs from 330mm to 350mm in the same 34mm thickness provides an increase in thermal mass, which means you have a larger heat sink to store brake heat. The larger disc diameters spread brake heat over a larger surface area, improving heat radiation. The advanced internal vane design of the AP Racing J Hook pumps considerably more cooling air through the discs, which reduces the amount of heat soak in your brake pads, calipers, and fluid. The AP iron disc metallurgy is more resistant to cracking, and our 350mm discs don’t have any weight penalty vs. stock despite their larger size. The J Hook slot design distributes heat evenly around the disc face and reduces uneven pad transfer, and the J Hook slots are less likely to crack than a drilled hole. The larger J Hooks also look better and fill the wheels up a bit more! These features all converge to ensure that your brake discs will run cooler than your stock discs, have less heat transfer to your other brake components, less propensity to crack, and a offer a considerably longer service life for your discs, pads, and fluid. In summary, there is no downside, yet a whole bunch of upsides to running our 2-piece J Hook Discs on the racetrack.

• Note- A common question we receive is, “If I upgrade to your 2-piece J Hook Discs that mate to my stock calipers, will I later be able to add the AP Racing calipers? ”The answer is unfortunately, “No”. The AP Racing Radi-CAL calipers run on discs of different dimensions vs. the stock calipers. One of the biggest differences is that the radial depth of the AP and OEM discs are considerably different (radial depth is the height of the disc face…the difference between the outer diameter and inner diameter).To learn more about why discs aren’t easily interchangeable, please watch our video, “Will the Brakes From a Different Car Fit my Car? "Again, if you choose 2-piece brake discs to mate with the OEM calipers, and later decide that you want a complete brake kit, you will need to essentially start over and buy the complete brake kit , including the new discs designed to mate with the AP Racing calipers.
• The next logical question then becomes, “Will your 2-piece discs be enough for me, or should I go with a complete brake kit?”That depends completely on your car and how you plan to drive it. Our earlier discussion about modifications, tracks being driven, etc. all factor into how much brake heat capacity you will require. If you plan to stay at stock power, on street tires, running a relatively easy braking track, and you tend not to be terribly hard on brakes, then 2-piece discs may be ample for your needs. If you plan to do a Stage 2 tune, run racing slicks, frequent Watkins Glen, and you tend to be hard on brakes, a complete big brake kit will be a much more appropriate option to provide you the fade resistance and durability you’re likely seeking. If at any time you want more personalized recommendations for your specific needs and situation, we will be happy to guide you through this process based on our prior experience with thousands of Porsche clients.
  • Front AP Racing J Hook Disc Pair for the 991.2 and 992.1 Carrera T
  • Rear AP Racing J Hook Disc Pair for the 991.2 and 992.1 Carrera T

Choosing a disc size

Once you have decided which AP caliper width and finish you prefer, your next choice is disc size. We offer one kit with larger discs, and one with smaller discs. Please note that once you choose a disc size, you cannot later change your disc size. For example, you cannot purchase our rear 365mm kit, and later decide that you want to run our larger rear 380mm discs. The rear calipers have different piston sizes depending on which disc size you choose, and the caliper brackets and disc hats are all completely different in the two kits and are in no way interchangeable. Once you have chosen a kit size, you have no options to change your disc size on the front or rear, so please take your time and choose wisely! Also, the larger front 390mm kit should be paired with our larger rear 380mm kit, and our smaller 372mm front should be paired with our smaller 365mm disc kit. Which disc size you choose should be determined by:

• How much thermal capacity you want/need (based on your modifications, intended tracks, driving style, etc. as discussed above). Our larger 390x36mm discs are considerably more durable than the 372x34mm discs, which are immensely more durable than the OEM 330x34mm discs. The downside to the larger 390mm discs is that they are slightly heavier than the 372mm discs. However, the largest 390x36mm discs still only weigh about the same as the OEM 330x34mm discs, despite the huge size difference!
• What size wheels you plan to run. Our 372mm disc kits can fit inside wheels as small as 18”, but our 390mm disc kits generally won’t fit in anything smaller than a 19” wheel.
• “So, should you go larger or smaller?” If you aren’t worried about shaving every ounce of unsprung weight, you discover that our 390mm discs will fit the wheels you intend to run, you want the greatest durability out of your discs, and plan to add a huge slug of horsepower to your car while driving tracks that punish brakes, choose our larger disc option. If you want to gain considerable thermal mass while still shedding as much unsprung weight as possible, and want to run the smallest, lightest weight wheels possible, our 372mm kit would be your choice.

Some imagery from the article: