TRAKCAR

Tik

Looks awesome, Joe! My kit is installed as well and I will be on the track this Friday. Look forward to comparing notes.

PwAg

Thanks for informative thread Joe. You will like this kit. Run near identical setup on a dedicated track E92 M3 (3150lb, full-cage, JRZ RS Pro, stroked 4.6 etc). Plan to add it to incoming .2. You really nailed your GT Silver spec, admittedly it got me second guessing my current GR choice.

Dr.Bill

Are the AP racing pads a little smaller?
It looks like the swept area of the rotor is smaller. Or is that an optical illusion based on the hubs?

I vote for just removing the logo on all 4 calipers. Looks better without. Maybe your 'accident' was fortuitous!

drdonger

The brakes look great. If the calipers came in red I would probably get them.

Palting

Appreciate the blow by blow photo install, Joe. Looking forward to your review on their performance. I plan on getting these exact same brakes when it's time to change the pads, and will be referring to them.

Clark-ApexPerformance

Dr Bill,

The swept area of the pad on the front AP BBK (they are actually Ferodo DS1.11) is 54MM. Your 991 GT3 Brembo calipers take a pad that has a swept area of 62MM.

PwAg

Beyond std dark gray, last I heard, you should be able to get them in red or black. I have them in red (anodized paint). Not sure who is recommended these days to get a custom AP order, as it's been years since I bought this kit. Perhaps Stillen in CA? Ask Essex as well.

Palting

Okay, so the swept area is smaller?! It's a little disheartening.

Yargk

Nice work, looking forward to on track impressions!

porscheflat6

Great information and thanks for posting

orthojoe

Well, I'm back from Weathertech Raceway Laguna Seca. Perfect weather, but I had problems the entire morning with passing sound. The problem was that the vacuum line to the exhaust flap actuator on the driver side kept blowing off. Zip tie wouldn't hold it down either. First session was fogged out. 2nd session black flag after one lap for sound. 3rd session black flag after 2 laps for sound. That second lap happened to be the fastest of the day. 1:36.3. I had to run to the parts store to find a new vacuum line to replace the OEM one. After that, the car was good for passing sound with the GPS device. My prior best in the .1 GT3 at Laguna was 1:36.9. I should be able to do a 1:35 if I can get my act together for T4 and T6. Someone really good should be able to do 1:34. Pobst will probably do 1:33.


The AP brake system:

Braking power is no different than OEM given that braking is limited by the tires and not the braking system
I initially thought I had problems with pad deposits because of shuddering under braking and problems with stopping distance.
HOWEVER, I figured out that it was ABS causing the shuddering and my problems. Duh. It turns out that the new system requires MUCH less pedal effort and travel to hit threshold. After I figured it out, I really appreciated the new system because it didn't require the work and effort the OEM brakes required and I was able to easily trail into a corner. Once I figured this out, I really appreciated the AP system and I'm happy I went with it. It's less work all around with pad swaps AND footwork on track. LOL

Some nice pictures from the day:

JRitt@essex

Nice driving Joe, and glad the brakes got the job done for you! Thank you also for the detailed install notes and pics.

We've now had a couple GT3 owners mention that the pedal with our system is extremely high and firm. That's a common response across all platforms when migrating from OEM calipers to the Radi-CAL setup. The Pro5000R Radi-CAL calipers are incredibly stiff under actual load, as that is the core feature of their design. It definitely takes a little getting used to for most people. Those who have driven an actual racecar typically tell us that our setup feels a lot more like one (which makes sense, because it is a racing brake system!). One of the things I personally like about a high brake pedal in a manual transmission car is that it usually makes it easier to heel-toe. Trying to 'reach back up' to the accelerator pedal with the outer edge of your foot is never fun or easy.
Actual brake torque output with our system is spot-on with stock, so there won't be any weird front-to-rear brake bias issues. As Joe mentioned, stopping distances (or what people commonly call 'stopping power') is limited by tire grip. A properly sized brake system is not going to shave any significant length off of stopping distances, assuming the OEM system was dialed in correctly. The brake system is all about storing and shedding heat after repetitive stops.

The pad's swept area is just one small piece of a many part equation. The 54mm and 62mm numbers are not actually swept area in this case, they are the radial depth. The radial depth is the height of the swept area of the disc, from the ID (inner diameter) to the OD (outer diameter). The pad intended to run on a given disc matches that radial height or depth. Discs shed heat in several different ways...convection (fluid flow), conduction (two pieces physically touching), and radiation (waves into the air). If you look at the OEM PCCB vs. the OEM iron, you'll note that the PCCB has a far greater surface area. That is the case on just about every car that offers both an iron disc option and a carbon ceramic option. Why? Carbon ceramic doesn't shed heat in the same fashion as iron, and the internal vane structures in a carbon ceramic disc typically aren't nearly as complex as those in an iron disc. As such, they don't have as much cooling air moving through them, drawing out heat as it flows across the internal vanes. Therefore, the overall footprint of the carbon ceramic disc is increased to have greater contact with the air, which means more radiation of heat in waves. On an iron disc, having a large number of shaped vanes increases contact with the air that is actually flowing through the disc. As the air flows across the directional internal disc vanes (left handed and right handed on either side of the car), it collects heat and draws it out towards the outer edge of the disc, evacuating it into the wheel. One can think of the air as a liquid flowing through the disc (convection). The more efficient the disc is at shedding heat, the smaller it can become. If you can shed more heat through the internal vane structure, you don't need to actually go bigger on the footprint of the disc. You can think of it like 'brute force' vs. 'surgical precision'. It's just two different ways of trying to solve the same issue of heat storage and evacuation. You can go gigantic, or you can go efficient. On this application, our setup is sort of a little bit of both. If other fitment issues weren't involved, we could have certainly gone with a smaller disc diameter on the front and rear and still not had any fade issues. For example, our C7 Z06 brake kits have a 372x34mm front disc (54mm radial depth) and the rears are 365x30mm (42mm radial depth). We have yet to have anyone fade that setup under any conditions, on any track. Those cars are frequently 700-800HP, huge slicks, big aero, 3600 lbs.+

We have some brake systems with iron discs that are actually smaller than the OEM iron discs that come on the car. People ask, "How is that going to help?" Disc design is about efficiency, not just overall size. In NASCAR for example, they run 15" wheels and we use iron discs that are only 325mm or 328mm in diameter. That's on 1000HP cars that weigh 3,300 lbs., going 200 mph! The difference is, the discs are thicker and they have a ton of internal vanes, just like the ones in our GT3 brake system. Many of the pads and discs in the NASCAR setups also only use a 54mm radial depth pad. The Porsche 911 RSR in IMSA also uses an AP Racing Radi-CAL with a 54mm radial depth.

If we didn't go to a smaller radial depth on the pads and discs, we'd never be able to knock 30 lbs. off of the OEM brake setup. The reason why we can get away with this is that the AP Racing discs are far more efficient than an OEM style disc. The 84 internal vanes in the AP Racing disc flow a great deal more air than a pillar style disc. In this particular case, the outer diameter of the front disc in our setup is also larger than the stock iron (even though it has a shorter radial depth), which also spreads the heat out (just like the OEM PCCB vs. Iron setup).

Hopefully the above makes sense. The thing to always keep in mind is that you only want as much thermal mass as you need. You want the brake system to have enough heat capacity to provide fade-free performance. Anything further is just dead weight to drag around. I typically describe our usual scenario in professional racing. If a pro team wins a race and the brakes fall apart after crossing the finish line, they know that they sized the system perfectly for that race. It accomplished their objective without any unnecessary fat. In NASCAR for example, they have multiple brake setups with different caliper and disc sizes depending on the type of race (super speedway, road course, intermediate). They're always gambling and trying to run the absolute smallest brake package they can get away with, because they don't want any unnecessary unsprung mass to drag around if at all possible. In the aftermarket, we use the same concept, except we obviously recognize that our aftermarket customers don't have Budweiser or Home Depot writing them sponsorship checks for spares. As such, aftermarket systems are a built to be more robust. We want low mass to squeeze out tenths of a second, but we also want the components to last long enough to satisfy the customer. We're always looking to find that balance.

JRitt@essex

Thanks for the support, and we're glad you're enjoying them on the M3!

JRitt@essex

I can clear this one up...it can definitely be a bit confusing, and a question we get all the time. AP Racing has two importers/distributors in North America, Essex Parts (us) and Stillen. Essex handles all of AP's racing and competition components. We deal with all of the professional race teams in the various major series (NASCAR, IndyCar, IMSA, World Challenge, etc.), as well as club racers and track enthusiasts. We design and develop competition brake systems using AP Racing's competition components (Essex also offers all of AP's other racing components such as pedal boxes, clutches, master cylinders, etc.). All of the calipers we employ in our brake systems have a hard anodized finished, stainless steel or titanium pistons, AKB springs, high vane count discs, etc. Stillen builds their own brake systems using AP Racing's road car line of products. The calipers in their systems are painted red, black or other colors, they have aluminum pistons, no AKB springs, they tend to weigh considerably more than the race calipers, they don't have as many race pad options, the discs frequently don't have as many vanes, etc. They are totally different product lines, with different goals, from different suppliers.

We don't do any type of custom colors, etc. I like to give our customers the Henry Ford answer: "You can get them in any color you like, as long as it's anodized gray!" Painted and powder coated calipers tend to fade, chip, etc. when thrashed repeatedly under track conditions, whereas anodized calipers hold up great for a very long time.