Originally Posted by enzotcat

Just about ready to pull the trigger on this (they are literally sitting in my shopping cart waiting for me to press the "checkout" button ) for my 991.2 C2S with 20" Carrera S wheels (and rear axle steering).

@JRitt@essex - two quick questions

1. Just to confirm - the customer example you cited above with a 991.2 C2 with 20" Carrera S wheels had no fitment issues, correct?
2. Other than the Ferodo DS2500 pads, what pads from other manufacturers fit the brakes. I've got nothing against the Ferodo pads at all - have zero experience with them - but am curious as to what my options are if I don't like them. Is there anything "special" about the calipers that requires some kind of special pad shape?
3. To confirm as well - you recommend completely removing the heat shield for these brakes. I have to ask the question - what is the downside of removing this heat shield? Surely Porsche had a reason for putting it on in the first place. What am I compromising as a result?

Thanks!

Originally Posted by JRitt@essex

Good question! Brake bias and balance are a confusing and messy topic. I've been involved in about 743 discussions on this topic over the past 20 years participating in various automotive forums. After 43 pages of discussion, people still tend to walk away a bit confused!

The three factors that impact brake torque are:

1. Disc effective radius/diameter- How far does the caliper sits away from the hub? As the caliper is pushed further out, the lever arm gets longer/there is a brake torque increase with all else held equal.
2. Total caliper piston area- As the overall piston area increases, there is a greater clamp load on the disc with all else held equal.
3. Mu (coefficient of friction) of the brake pads- How much friction do the pads generate? As the mu increases there is an increase in brake torque with all else held equal. Pad mu is typically held constant in all discussions of swapping out calipers and discs, with the assumption that the same brake pad compound can be run in the OEM brake calipers or the aftermarket ones. A major complication with the mu value of a brake pad is that it is constantly changing with temperature. It usually rises step-wise with heat until the pad compound's fade point/max operating temperature is reached, at which point the pad no longer generates much friction.

Our Road and Competition Brake Kits are all designed to very closely mimic the OEM brake torque output at both ends of the car. That is accomplished by carefully and concurrently sizing the discs and caliper pistons. One is not altered without taking the other into consideration. For example, if we increase the disc diameter in our front kit vs. stock, we decrease the overall piston area to produce the same overall torque output as the factory setup. As such, installing our front kit on your car while leaving the rear stock would only have a negligible impact on brake bias. In most cases, the shift in brake bias is only in the 2-3% range. To put that in perspective, installing a more aggressive racing brake pad compound in your factory front calipers (and heating them to track temps) while leaving everything in the rear alone, would typically have a greater impact on brake bias than installing our front kit while using the same front pad compound you were using previously.

More specifically to your point regarding an asymmetrical increase in disc size at one end of the car. On your car for example, the increase in disc size vs. stock is larger in the rear 330mm --> 380mm vs. the front (350-->380mm). Having proper brake torque and balance is just a matter of having the proper piston bores in the rear to counteract the larger relative increase in disc diameter. The ABS system is programmed using a specific torque output based on the disc sizes, caliper piston sizes, master cylinder, etc. There is a fairly narrow window in which all these parameters must fall, and that window has shrunk as ABS systems have become more sophisticated. If you were to install a combination of disc size and piston bores that diverges too far from stock, the ABS system can go into a tizzy. This is something we often seen when people take the OEM brakes off of one model or trim level and put them on a different model or trim level for which those brakes were not designed. In the Porsche world, it's usually someone trying to apply GT3 brakes to a lower trim level. In the BMW world, it's someone trying to install Mercedes AMG brakes on an e92 M3. In the Subaru BRZ world, people try to install larger WRX STI brakes on their car to gain more heat capacity. When that is done however, there is no adjusting the pistons sizes. The components are what they are, and when mated to a disc of a given size, the brake torque output is not variable. Our situation is a bit different however. We have a range of calipers that appear identical on the outside, but have slight variances in the piston sizes. As such, we can tailor our systems to match specific brake torque outputs as needed.

When people install the OEM brake components from another car, they are many times trying to achieve an increase in brake heat capacity, which is the fundamental reason for upgrading to a big brake kit in the first place. While in many of these cases the calipers and discs will physically bolt onto the car without any modifications, that doesn't mean they will actually be optimized on the chassis in question! Blindly slapping a bunch of larger components on the car without considering the brake torque output at both ends of the car is a recipe for issues. If the combination of disc and caliper piston sizing diverges too far from what was initially installed on the vehicle in question, the result is typically premature ABS intervention, longer stopping distances, etc. In other words, the brakes may look cool, fill the wheels, and even provide a larger heat sink. However, if the brake torque doesn't match what was on the car in the first place, they can be a substantial step backwards in terms of performance.

When done properly with the correct components however, a big brake kit not only provides the increased heat capacity one is typically seeking in larger brake components, they also offer superior response, stopping distances, ABS intervention, etc.

Here's a video we shot on our brake kit design process. In this case I'm speaking about our Competition Kits, but the same things all apply to our Road Kits as well:
https://youtu.be/46HyPkF_2RA

Originally Posted by Dark_horse

Almost ready to pull the trigger on the road kit. One question I have is that after 30k miles of driving on the street my rear brake pads and rotors are almost gone while the fronts still have plenty of life. Will this kit solve the rear brakes wearing out faster issue?

Originally Posted by Dark_horse

Ummm I see, Yes 30k is not bad but I'm used to the fronts always going out first on every other vehicle I've owned.

Originally Posted by Dark_horse

Almost ready to pull the trigger on the road kit. One question I have is that after 30k miles of driving on the street my rear brake pads and rotors are almost gone while the fronts still have plenty of life. Will this kit solve the rear brakes wearing out faster issue?

Originally Posted by enzotcat

Just got my car back with the new BBK installed. Just from an initial drive, the stopping power seems to be more than the stock rotors, and apparently I essentially went through my stock brake pads (7mm remaining on the front, 4mm remaining on the rear) in 2 track days (9 x 20 minute sessions) with the upgraded power, so this is a timely upgrade. Hopefully the DS2500s will last a little longer, but I'm not gonna hold my breath on that based on what I've read. Opted for the red calipers to keep as much of a stock look as possible.
Well they at least look more powerful .

Originally Posted by JRitt@essex

What tracks are you running? Thanks so much again for your support!

Originally Posted by JRitt@essex

The front vs. rear pad wear issue is a function of the vehicle layout. Because of how the weight is positioned and transfers on a rear engine car, the rear brakes have a greater contribution towards scrubbing speed than on a front engine car. Also as noted above by enzotcat, if you are using driver aids like yaw control as noted above, rear brakes tend to wear more quickly because the car is using the rear brakes to help tuck the nose in turn.

The primary benefit of a big brake kit is to resist fade after repeated stops as one would experience on a racetrack. The discs, pads, and calipers work together to reject, absorb, and shed more heat than the OEM brakes can. That is typically accomplished through greater thermal mass (larger discs), superior efficiency/more airflow (disc and caliper design), and specific materials designed to reject heat (disc metallurgy, caliper piston material, brake pad compound, etc.).

Originally Posted by enzotcat

The ones I did earlier this year were Lime Rock Park, CT and Club Motorsports in Tamworth, NH - those were the ones that nuked my brakes. Prior to upgrading my turbos and tuning the car I'd get 6-7 track days out of the stock brake pads. I suspect the extra speed I'm carrying as a result of that caused much more heat buildup, which in turn made my stock pads last less long.

I have a couple more track days scheduled for Club Motorsports later in the year, and have some scheduled for New Hampshire International Speedway as well. I may make it to Thompson Speedway, CT, but that's a little up in the air at the moment.

Originally Posted by Dark_horse

I went to my cart to Purchase the brakes on the 20th and they were back to full price. I guess I read the dates wrong as I thought the last day was the 20th.