I thought I'd share a few things I've learned over the past years of endless tinkering with my Boxster S, one area being the brakes.

Disclaimer #1: Brakes are a critical safety component of your vehicle. All information presented here is for "entertainment purposes only". I'm not liable for anything. You get what you pay for, etc.

Disclaimer #2: For those that are convinced that THEIR Porsche is the finest product that Porsche has ever engineered and can never be improved upon, please move on to another post. There is nothing here for you.

Okay. With that out of the way, the first question that needs to be asked is why mod your brakes? Porsche equips their cars with some of the finest brakes on the planet. They are made by Brembo, but I hesitate to call them Brembos because Brembo does not sell them, rather they are made by Brembo to Porsche specifications. One particular feature/quirk of Porsche brakes is that they use a very large annulus which you just don't see in other brakes. This is an important feature to note. Another important thing to note is that Porsche brakes are in high demand by the VW, Audi, and Volvo crowd so you can fetch a pretty good price for your old brakes on the used market.

Some reasons to mod your brakes:

* More brake torque--this is generally not a major concern unless you're running sticky rubber. Most stock brakes can lock street tires.
* More heat soak/dissipation--once you get past green pad fade, this can be a problem, but not one you're likely to encounter in street driving--more for track or serious hard backroads/canyon driving.
* Bling--You've got 19" wheels and those brakes look tiny.
* Optimization--although your stock brakes typically have no problem locking up street tires, a LOT can be done to optimize the setup, especially in terms of operating temperature ranges, friction, and brake bias.

Background information: Brake torque is largely determined by three factors: (1) the combined area of the pistons in the caliper (F=p*A), (2) the effective radius at which the pads are gripping the rotor (T=FxR), and (3) the coefficient of friction of the pads (mu). So, all else being equal, going to a big brake kit (BBK) 318mm -> 350mm only gives you about 10% more brake torque. That can easily be obtained with a pad change. Further, that BBK probably may also have added unsprung weight and shifted your brake bias even further to the front. So, you spent $2K, have worse braking, but increased heat soak and added bling. The moral of the story is you really have to understand what you are trying to achieve. For many people, the stock brakes are just fine. Don't worry.

What not to do: I read over and over that the front brakes do most of the work, so just upgrade the front brakes. Unless you are trying to improve the heat soak of the front brakes (rotors), a big brake kit for the front can reduce your braking ability by further increasing front brake bias and possibly increasing unsprung weight. Some manufacturers, like StopTech, do take brake bias into consideration, though.

I've read and researched a lot about brakes and done a number of things which I'll group into arbitrary stages below. There are a number of folks out there with tremendous brake experience as well--some who have even gone so far as to custom fit PCCB, but I just wanted to share my experiences and knowledge. This is not the be-all end-all of information.

 

This is just optimizing the brakes you already have, and a lot can be done in this area.

* Regularly change your brake fluid and use something appropriate for the type of use/abuse.
* Properly corner-balance your car and make sure your suspension is up to snuff so that all of your tires are as evenly loaded as possible.
* If you need additional heat dissipation, look into available brake ducts (Porsche calls them spoilers) from GT3s and such for better cooling.
* Use braided stainless lines if your OEM ones are old.
* Try potentially several different pads or get some good recommendations. Sometimes it is hard to find this information from manufacturers, but you want a stable level of friction (mu) over the operating temperature that you plan on using. Don't make the mistake of fitting racing/track pads for street use as you will not get enough heat in them during normal driving. In the worst case, when they are cold and wet, they will not work, and you will rear-end someone.
* Try fitting higher to much higher friction compound pads in the rear. I have found way too much front brake bias in my Boxster, and shifting the brake bias to the rear leads to very real gains, say on the order of 0.1Gs. Note when trying this trick, it is VERY important to use pads that have very similar friction/temperature curves.

To be honest, I was very disappointed with my stock brakes, but after playing around with "Stage 1" mods, corner weighting and pads in particular, I found some handsome gains in braking and was quite satisfied. The limits I ran into were that there were just limited selections of pads with similar friction/temperature curves (shapes) but with high differences in absolute friction to cause a significant increase in rear brake bias.

 

This is where I started getting crazy. Through an absolute fluke, the front calipers off a base Boxster (298mm x 24mm) fit the rear brakes of an S (299mm x 24)--or non-S 996. Actually, the pads are a mm or two taller in which case the pads may hang off the edge of the rotor by a mm or so. The whole reason for doing this is that the pistons in the front calipers are significantly larger than the stock rear pistons. Porsche uses 28mm and 30mm pistons almost exclusively for all their rear calipers. The front pistons in this case are 36mm and 40mm giving a whopping 72% increase in rear brake force. To my surprise, I didn't die, and the ABS still wasn't engaging the rear brakes. Even putting in higher friction compound pads in the rear (with an accordingly absurd amount of rear brake bias), I was able to get the rear ABS to engage, but even trying to get the rear end loose, the ABS held and did it's job. As a side note, on the 997 GT3, Porsche increased the rear piston sizes to 34mm (about a 37% increase). With this setup, I probably got about 0.1Gs out of the deal.

To do this stage 2 mod, you need to buy a set of new base Boxster calipers (don't bother with used). I got mine from Sunset Porsche. I freshly painted them with G2 caliper paint and used Xenonmods stickers. To be honest, they look indistinguishable from stock except the color is a hair off. Porsche's red actually has a hint of orange in it. Then, I eBay'ed my old calipers for almost what I paid for the new calipers from Sunset. Net, including paint and another set of pads was like $200. Not a bad upgrade.

P.S. Here's a picture of my Stage 2 rears:

 

So why even a stage 3? Well, I wanted even more rear brake bias. The only way to do that was to increase the rear rotor diameter. I also wanted aluminum 2-piece floating rotors. Why? The same reason why people "need" a 911 Turbo or a GT3. I'd spent a couple years researching all the dimensions and trying to find someone to fabricate the custom rotors. There are a couple places out there, but honestly, I was not impressed with their quality. A huge problem that you run into is that there are almost no rotor blanks out there with an annulus big enough to fit Porsche calipers and pads. In fact, that causes a problem with the Performance Friction 2-piece rotors--they use steel hats which weigh more than OEM and have pad height interference problems. In order to fit aluminum hat hardware, you must grow the diameter of the rotors (front and rear). Well, I finally found a company that would make the custom rotors for me. I have no affiliation with the company and will post the name later since I'm not even sure they're set up yet for volume production of these rotors. The quality of the work is really too nice to even mount on a car. The top guns in the company used to work for Porsche and Brembo. They know what they're doing, and they have some nice equipment. Their work is pure eye candy. They were also patient enough to work with me for OVER 1 YEAR with countless measurements and prototypes. The incentive for them is they are also making a Cayman S set (which would also likely work on Boxster S and non-S 996s/997s) with minor differences to mine.

I still need to change my front tires, but now that they have been fully broken in, I can say that I am quite satisfied with my stage 3. The braking is really insane, and the brake bias is about dead perfect. My brakes are 340mm front and rear with excellent cooling and heat soak. Considering the aluminum hats, I saved 2 lbs per corner in the front, but lost about 3 or 4 lbs per corner in the rear. My goal was to net very close to stock weights and front unsprung weight is more noticeable to me. I also retained the parking brake. Considering that PCCB saves 50% but this is over the weight of 350mm steel rotors, I figure I'm within a pound or two of PCCB but with slightly smaller rotors and with a lot less cost. With steel rotors, I can also trash on them as much as I want and use any odd pad. With PCCB, I'm sure there is even more ultimate heat soak/dissipation capability, but for my needs and for the weight of my car, my setup is perfect--for me.

I'm posting this first on 6Speed since it is a rather mod-friendly board and it is a Boxster/Cayman board. I know there are strict rules on selling/sponsoring. I am not affiliated with the company that made my custom rotors, but will post their contact info and rough pricing once I talk to them and see where they are in supporting Porsches in a more general production manner.

P.S. Here's a picture of my Stage 3 rears. Note, these are cross-drilled (spouse-friendly) one-offs. All "normal" rotors will be slotted.

 

Finally, I snapped an overall pic of my car.

 

long read, but good. very detailed info