GrantG

Don't worry - they won't stay Yellow long when used like this

CRex

OP, you can also pilfer the GT2RSCS parts bin for all its cooling parts.

The underbodies of the two cars are very similar, and the CS is basically max cooling you can achieve.

M3the01

Front splitter, diffuser are different, along with the hood and scoops for the brakes on the CS. The carbon front splitter is really a work of art.

JRitt@essex

After helping many thousands of track day and racing customers with brakes, and more specifically hundreds of 991 GT3 owners, our advice is to skip Carbon Ceramic discs in all forms. We suggest a proven solution that will last longer, perform better, and doesn't have the obscene long-term running costs of carbon ceramic. Our AP Racing by Essex Radi-CAL brake system offers a huge list of performance and convenience benefits. Best of all, it will also preserve your OEM yellow calipers.

You can see lots of owner comments in this thread:
https://rennlist.com/forums/991-gt3-...inally-20.html

We also have tons of owner feedback on our blog:
https://www.essexparts.com/news-blog

Aftermarket carbon ceramic discs, regardless of whether they are short or long fiber, have many downsides:

• Incredibly expensive
• Still don't last as long as a proper set of iron racing discs during repeated track abuse- they still oxidize at track temps, regardless of whether they are long or short fiber
• Run significantly hotter than iron discs, putting more stress on your caliper piston seals, brake fluid, and surrounding components.
• Your OEM calipers get used and abused- heavy, not easy to remove pads, limited pad choice, piston seals get cooked
• Short fiber discs are trash after they oxidize. Long fiber discs require resurfacing...must be shipped to manufacturer...many times in another country ($$$), the car is down for some period of time while discs are off the car, discs can only be resurfaced a limited number of times
• Limited pad choice as noted in posts above
• Limited wheel choice since the discs are so physically large
• Discs are damage prone- knocks from wheels, track debris/rocks, wheel cleaners, etc. can all damage carbon ceramic discs
• Greater sensitivity to bedding/burnishing
• Poor feel relative to your favorite iron disc and pad combo

Why not just cleanly replace the entire system, and preserve your OEM PCCB brake system for when you sell your car? Compared to aftermarket carbon ceramic discs, our iron AP Racing system:

• Eliminates the need to remove the caliper for pad changes
• Saves 33 unsprung lbs. vs. OEM iron brakes and weighs almost the same as the OEM PCCB system
• AP Racing Radi-CAL with durable, ventilated stainless steel pistons (no ceramic piston caps to break) with anti-knockback springs
• Allows for the preservation of pricey OEM brake components
• Huge array of brake pad options from all major pad manufacturers
• Clears OEM 20" wheels without a spacer
• 394x34mm, 84 vane AP Racing disc fits inside many popular 19" wheels
• Every component designed to resist the heat of extended track sessions
• Pistons sized properly to allow for seamless integration with OEM master cylinder and ABS system

When the discs in our system are used up (which typically takes a very long time), you simply buy and install a new set. You don't have to pay to have them removed, ship them off to another country, wait for them to return, and hope they get back to you in a timely manner. In most cases we can ship them out on the same day they're ordered.

Our system is as close to one can get to the AP Racing Radi-CAL brake system used on the 911 RSR. Over the past couple years Porsche has won Le Mans a couple times on an iron setup with AP Racing Radi-CAL calipers, so please don't allow anyone to tell you that iron isn't good for the racetrack!

Also of note...We are a longtime paying sponsors of the Rennlist community. We don't encourage individuals to sign up for an account to post commercial messages about our products under the pretense of being an anonymous fellow enthusiast.

JRitt@essex

FYI, I just finished up the first part of an article I've been working on about carbon ceramic discs for track use. I'll post a link here very soon. Thanks gents.

LSs1Power

Im thinking about replacing the discs and pads only and keep using the yellow Porsche calipers.

How does the AP J discs compare to Girodisc steel rotors?

Also anyone worked on larger brake cooling hats front and back?

JRitt@essex

Understood on the discs/pads. Among clients who have used both both brands, we are typically told that our iron discs offer longer life. In most cases, they actually tell us the same thing regardless of what brand they were previously using. It's not uncommon for us to get this type of feedback: https://www.essexparts.com/news-blog...g-j-hook-discs

From what we've also seen, the anodizing on our disc hats appears a bit more robust, and a bit less prone to shifting colors from black to maroon/purple. That said, any anodized disc hat is going to shift colors somewhat when enough heat is repeatedly introduced. Our discs also tend to be a couple pounds lighter than many of our competitors, but I'm honestly uncertain about the weight on this specific application since Girodisc for some reason doesn't publish their weights. The J Hook slot pattern on AP discs is the optimal choice for evenly distributing heat across the entire disc face, while having six or eight straight slots on the disc face leaves cold patches in between those areas. Even heat distribution from the J Hook slots promotes a more even transfer layer of material/less likely to have vibrations, and can contribute to disc life. Having the high number of J Hooks also gives more leading edges for the pads to bite into...similar to drilled holes, but without the propensity to crack at the edge of the holes. The price of the AP Discs is slightly higher, but that difference is offset by longevity. I'm not sure if it matters to you, but AP Racing has a much stronger history in racing at the elite level, and is widely considered the global technology leader in brakes. Finally, we are forum sponsors, community supporters, and I don't know of anyone in the brake game who offers the same level of customer service that we do.
We do like the Girodisc guys though...nothing wrong with the product or the people over there. We always chat when we see them at trade shows, etc.

I'm not sure what you mean by 'brake cooling hats'. Are you talking about brake ducts?

Thanks!

JRitt@essex

If you don't believe me, some of Porsche's internal staff even admit that iron is superior for track use vs. carbon ceramic.

JRitt@essex

One other important benefit of the AP Racing J Hook that I forgot...they look really cool!

JRitt@essex

Below is Part One of the article I mentioned above. In part two I will go into greater depth on options/solutions for those who already have carbon ceramic discs. For those who plan to track their car and haven't yet gone down that path, we'd suggest sticking with iron to save yourself a lot of time, money, and headaches. Some people will post here and tell you otherwise. I'd suggest understanding who you are dealing with, and from where they derive their recommendations before taking their advice as gospel. Our observations and recommendations are based on directly assisting many thousands of professional and amateur racing clients with brakes since 1983.

Are carbon ceramic brake discs better than iron?

LSs1Power

thanks for the Technical answer, yes i meant larger or better design brake ducts for tracks like BIC which require heavy braking.

Perimeter

This is exactly 180 degrees opposite of my experience.
For the first time in 4 gt cars I ordered Steel Brakes and absolutely hate them.
Compared to the PCCBS I have had before on 997.2 GT3 and GT4 these steels have terrible feel, lack depth of breaking and I need to apply the peddle MUCH sooner than PCCBs.

I understand 99% of your argument is price stated in one way or another and agree, but I do not agree on peddle feel or braking depth

Lander992TTS

I swapped the pccb’s on my 3RS for the AP/Essex kit with j hook rotors last summer and I’m impressed. (I kept the pccb calipers). Braking performance is as good or a little better than the pccb’s in my opinion, and the pads and discs are affordable.

CRex

Not sure what you're talking about with the front splitter. Any chance you confused the CS' splitter (a plastic piece with attachment points just like a Cup Car) with the 935

JRitt@essex

With the proper discs, pads, and calipers on these cars, the factory brake ducts should be sufficient. Properly implementing cooling ducts on a road car is extremely difficult for a variety of reasons. Here is an article I wrote on that topic last year:

Do I need brake ducts on my track car?

With the correct discs on the car, your disc temperatures should be manageable with the OEM brake ducts. For reference, the modified matte black GT2RS in the picture above was being flogged by a pro driver at Circuit of the America on Pirelli P Zero DHA slicks and had no brake fade or problems. As noted above, carbon ceramic discs tend to run considerably hotter than iron. That's why they have such a large swept area (along with their corresponding pads), for heat radiation, since they don't use intricate internal cooling vanes to move cooling air and evacuate heat.