fsmich

Hmmm, your 991.2 GT3 kit is sized with 394/380 rotors. A tuned 991.2 GTS is faster AND heavier than a GT3. Why the 372/365 setup?

JRitt@essex

Because on the GT3, we HAD to go bigger. We literally didn't have a choice from a technical perspective, or we would have gone smaller to save unnecessary weight. The 991 GT3 comes with a 380mm disc from the factory, and the caliper is oriented on the suspension spindle to accommodate a disc of that size. If the AP Racing and OEM calipers had attachment bolts that were the same distance apart, you could potentially bolt the AP Racing caliper directly to the suspension upright, and run them on a 380mm disc. However, the mounting bolt spacing on the OEM calipers is wider than the bolt spacing on the AP Racing calipers. That means a caliper adapter bracket is required to fit the AP Racing calipers to the car. As soon as you sandwich a caliper adapter bracket between the spindle and the caliper, you're pushing the caliper further out towards the wheel barrel, and mandating the use of a larger diameter disc. The caliper is now sitting further away from the wheel hub, and you need a disc that reaches out further to the caliper. Our 372mm system is more than ample for a GT3. If we could have used a 372mm/365mm on the GT3, we would have. It physically doesn't work on that car however due to the brakes and suspension that came on it from the factory.

Bigger is not always better. Efficiency, design, materials all have a dramatic impact on brake capability. Our Competition Kits in particular are derived from a racing mentality. In the pro racing world, teams scrap and scream to remove ounces of weight from the cars. Anything that is larger than necessary to get the job done is simply dead weight to drag around. That is how we approach our design. If you want to go faster and a 14" disc will work, a 15" disc will simply add weight, increase the moment of inertia, and hinder wheel fitment. Sure it will look pretty behind 20" wheels, but that's not what this product line is about.When comparing discs, you can't simply look at the diameter and decide that one will be more effective than another. The number of vanes, air gap, wall thickness, vane shape, metallurgy, hat attachment design, etc. all have to be taken into account. It's not just disc size that matters. It's all about design and optimization.

Wheel fitment is also of critical importance in our design process. As mentioned above, most of our customers run the smallest, lightest wheels available for the platform. I won't go into all of the merits of doing so, but obviously unsprung weight, lower rotational mass, cheaper tires, etc. all factor in. Our systems are packaged tightly to allow for a wide range of wheel fitment. Using an extremely large diameter disc kills wheel fitment, and the utility of a track-optimized brake system.
Another example...The F87 M2 Comp is one of our best brake kit sellers for precisely the reasons above, and the F87 M2 Comp is harder on front brakes than a 911 due to its weight, drivetrain layout/weight distribution, turbo engine potential, etc. With the engine hanging behind the rear axle, the 911 uses less front brake and more rear brake than an M2. The F87 M2 comes with OEM front discs that are 400x36mm and weigh 30.4 lbs...and it won't fit inside an 18" wheel. Our 372x34mm front system for that car has ample heat capacity, shaves 26 unsprung lbs. from the nose of the car (the 372mm discs weigh 21 lbs. each), and fits inside 18" track wheels. The AP disc design flows far more air and has superior metallurgy, so it doesn't have to be gigantic to get the job done.

Again, bigger isn't always better. Design, materials, and efficiency are all very important!

Okay...now that we're clear on all the above...if you really do want a larger disc, as 4.0 mentioned above, we just recently released two front systems for the 991 GTS that runs on a 390x36mm disc. This system was originally developed for the 992 Turbo S. There are two caliper choices:

Narrow front caliper (CP9661)= https://www.essexparts.com/ap-racing...-992-turbo-ENP
Wide front caliper (CP9669)= https://www.essexparts.com/ap-racing...-992-turbo-enp

The front disc we use in the systems above has considerably more thermal capacity than the 394x34mm disc in our GT3 systems, and more thermal capacity than the 380x36mm discs in our Road Kits. So, if you plan to throw stupid horsepower at your GTS, these could be the ticket for you.

Below is a note from one of our broadcast emails announcing our new 390mm kits for the 992.1 GTS. Again, this is another case like the F87 M3 above, in which we reduce the size of the OEM brakes, maintain ample thermal mass, and dramatically reduce unsprung weight (comparable to PCCB without all the carbon ceramic disc nightmares).

Carrera GTS

The story with the 911 GTS is more of everything, and that includes the factory brakes. Torn from the monstrous 911 Turbo, the fronts feature a ten-piston caliper over a 408mm or 420mm (PCCB) discs, mated to a 380-390mm rear. The problem with the gigantic stock brakes is that they are extremely heavy and require huge wheels to cover them. Our solutions for the Carrera GTS actually reduce the size of the brakes vs. stock, with the goal of unsprung weight reduction and superior wheel fitment while still offering ample thermal capacity. Here's the really cool part...our four-wheel Radi-CAL Competition Kit with iron discs weighs almost identical to the OEM PCCB setup, and can shave as much as 50 unsprung lbs. vs. the OEM iron brakes depending on caliper and disc choice! That doesn't even include the weight savings available from smaller, lighter wheels and tires, since our kits will fit inside wheels as small as 18" depending on the chosen disc size.

I'm happy to offer more specific guidance on which of our brake kits is most appropriate to anyone who wants to tell me more about their personal goals with their car.

JRitt@essex

Also...not sure if you've seen it, but a few months ago I wrote a 911 Brake Upgrade Guide which can be found here: https://www.essexparts.com/news-blog...qIGyokkgZKE5rn

I haven't yet had a chance to add the new 390mm kits into that article, but I need to do so. Thanks!

thesaintusa

@JRitt@essex

On your website it mentions that if you run your car in the winter to try and avoid the Competition kit.

Will the Road kit work with a 19" wheel?

JRitt@essex

It's going to be very, very tight with 19" wheels, and will depend on the specific wheel. We publish wheel fitment templates for every brake kit we offer. Your best bet is to use our template. Below is some guidance on where to find those and how to use them:



This is me fumbling about with one of our templates.

JRitt@essex

The only significant difference with using a Road Kit or Competition Kit in the winter is the piston dust boots. Dust boots keep gunk from accumulating on the sides of the pistons. As long as you're sure to wipe the sides of the pistons down before pushing them back into a caliper during a pad change, you've accomplished the same thing as a piston dust boot. That's literally all they do. Frankly, the ENP Competition Kit caliper finish would be just as durable for winter use as the painted road caliper finish. The anodized Competition Kit caliper finish would not be as durable to winter gunk, road salt, etc.

ANY aftermarket BBK will require similar maintenance and present the same problems in foul weather conditions. The most vulnerable area for problems is the attachment point between the iron disc and aluminum hat. That's why you don't see a whole lot of OEM two-piece discs using an aluminum hat. Over the years many OEM's (including Porsche) use a dual-cast iron design with as few moving parts as possible. What happens is, that road salt and other gunk gets wedged between the hat and iron disc ring, and it is essentially impossible to remove short of taking the disc apart. The salt eats away at the aluminum hat, eventually flaking, chipping, etc. Again, this is a problem that will be encountered on ANY aftermarket big brake kit. Also, the same sort of things happen with the caliper brackets on just about ANY aftermarket BBK. They're almost all anodized aluminum.

JRitt@essex

Also of note, our huge front 390mm kits will fit some custom 19" wheels. Again, you need to check the template with the specific wheel in question. If anyone needs a set of Forgelines, we are an authorized reseller of their wheels and we would be happy to put together a nice wheel/brake package for you.

Tier1Terrier

@Speed2k

The plot thickens a little bit here. I wanted to do some deeper verification. I've heard back from 2 different Ferodo suppliers (Essex and Apex) that the 991.2 Carrera S FRONT PAD ONLY for the DS2500 is indeed the same as the one for the GT3.

Accordingly, These pads should work for the 991.2 Carrera S as you originally stated. Great!
DS2500 Ferodo FCP4664H (GT3 size) -Front
DS2500 Ferodo FCP4713H - Rear

Unfortunately, I did not get a good confirming response about the Sebro rotors listed above from FCP Euro. According to a technical specialist at FCP Euro, he said regarding the Sebro rotors listed above "Unfortunately none of those rotors will fit your vehicle." His name is "Jason M".

Are there any actual FIRST HAND accounts of someone doing a direct swap on a 991.2 Carrera S with THESE SPECIFIC Sebro rotors? Or are you just assuming that because the rotor diameter and thickness is the same that it's a direct swap. (That would be a reasonable assumption.) The only thing I could imagine is if the depth of the hats are different then maybe there could be a fitment issue. Otherwise the person at FCP is simply responding with whatever their computer tells them but not necessarily having expert technical knowledge. Additionally, they would probably rather sell 991.2 Carrera S owners the more expensive 'OE/OEM' rotors than have them buy ones that are made for older generations even if the fitment is the same. That's just my cynical perspective but may or may not be the case. Regardless, I just spoke on the phone with someone there who confirmed that they only go by what the computer tells them, but they offered to have a Porsche parts "specialist" call me back to provide further clarification. I will update this post if/when I hear from them.

EDIT: I did find THIS THREAD where there appear to be only a few experiences with this pad/rotor combo. One of them @snake eyes discusses how he destroyed this rotor/pad combination after just 2.5 track days. Then there was some discussion as to whether or not he was just "unlucky".

Speed2k

Not surprised by the answer from FCPE. As mentioned in the other thread, it's been tried and it works. The first link in the first post was to @markk222 posts where he says that he installed these parts onto his 991.2 GTS.

As for the other thread, there are too many variables to say. Perhaps he's a fast driver on a track that's hard on brakes. Driving style plays a big part too; if you can, ask to sit in with some fast drivers at your next event (if allowed). Pay attention to the way they drive, you'll be amazed at the different driving styles, some are smooth drivers that barely turn the wheel, others seem to be fighting the car, making lots of corrections, but the end result maybe similar lap times. One is also likely harder on the brakes than the other. But a pad that had disintegrated would probably have ruined any rotor.

JRitt@essex

Also, if you read our guide on Ferodo pads, we have some notes in there about the limitations of DS2500.
https://www.essexparts.com/news-blog...s-right-for-me

People often choose to ignore those comments, despite my repeated warnings...particularly on heavy, fast cars. They do so because they don't want to bother swapping pads before and after track events. Having been through that process a million times, I totally get that. However, there's no free lunch with this stuff, and sometimes you need to put in the work to equip the car properly.

Clark-ApexPerformance

Not available from FCP Euro but looks like ECS has them:
DS3.12 Ferodo FCP4664G (GT3 size) - Front
DS3.12 Ferodo FCP4713G (stock size) - Rear

Apex Performance is selling the majority of the Ferodo DS3,12 pads into POrscvhes. Call for special pricing or advice. I will talk to you. 843 299 0997
Clark
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