JRitt@essex

The initial customer feedback from the launch of our GT4 kit is starting to come in as well (we launched that kit a few weeks after the GT3).

Below are pics from one customer, and another commented via email after a weekend at Road America, "The brakes are F'ing awesome!"

orthojoe

My initial write up on the AP brake system on my .2 GT3 for those that didn't see it:

https://rennlist.com/forums/991-gt3-...l#post14997017

I took off the wheels today to check out the pads. The rear pads still look new and the front pad barely look worn. This is after 2.5 track days. On my .1 GT3 the DS1.11 front pads would last about 6 days. I'm pretty sure that the DS.11 pads with the AP system will last at least twice that. Will find out!

JRitt@essex

Hello Gents,
We just got back from a great National Corvette Museum HPDE at VIR. We had over a dozen happy customers out there with our AP Racing Competition packages, and a couple were running sub-two minutes. The orange ZR1 was really cooking, and was hitting 162-163mph on the front and back straights.

We unfortunately only saw a lone 997 GT3 at the event, and zero 991's. I would have loved to see some GT3s mixing it up with the Vettes. We're hoping more of our GT3 customers will start checking in with track reports!

JRitt@essex

Thanks for checking in Joe! My hunch is that your pads and discs may very well last for forever and a day.

thebishman

Those brakes look awesome, Jeff. The ZR1 looks to be Por-Sha's car.

Bish

JRitt@essex

We weren't at the event, but we heard the AP Racing Radi-CAL had a pretty decent showing in France the other weekend as well.

JRitt@essex

Hey Bish...yep, he was blazing out there!

orthojoe

Damn. That pretty much settles it, doesn't it?

Todd B

orthojoe

Jeff, can you tell us what differences there are (if any) between the brakes used by the cup cars to win Le Mans vs. the brake kit for the street GT cars?

I'm also curious to know what the snobs who say people only option irons over pccb do it because they can't afford the 'best' have to say about this. I'm pretty sure the racing budget for pro teams is larger than their 'huge' budget.

race7117

Race teams only need the brakes to last the distance of the race, and although LeMans is a long race, it is not quite the same as designing a brake system to last over years of use for thousands of miles. I'm not saying that this brake system won't go the distance just that engineering for a race is very different than for long term street car. That being said Any way to use these calipers with a Ceramic Disc like ST makes? Wonder what the weight would be.....

Shandingo

JRitt@essex

Sure thing Joe. The Radi-CAL calipers used to win Le Mans are far more similar to the ones in our kit for the standard GT3 than they are different. They are both forged with a removable bridge, but the Radi-CALs on the RSR are a one-piece (monobloc) design, rather than the two-piece design we are using on the standard 991 GT3 and RS. A one-piece design allows for the elimination of the steel through bolts, which removes some weight from the design. Many people mistakenly believe that the monobloc is inherently stiffer, but the steel bolts aren't exactly flexible! Weight is the key driver for the one-piece design. That said, the front CP9661 caliper we're using in our front kits actually weighs about 3/4 of a pound less than the ones on the front of the RSR, but that is because the calipers on the RSR are specifically designed for endurance racing. As such, they have a larger footprint and can accommodate a pad that is 30mm thick (vs. 18mm thick on the CP9661). Along the same lines of endurance racing needs, the RSR caliper has a quick change spring clip on the bridge, so pads can be changed without hand tools. That design is just like the one shown below. Both calipers have stainless steel pistons with AKB springs, both have an anodized finish, and both have internal porting. One of the biggest differences is price. The caliper on the RSR costs a little more than double vs. the one we're using. Again though, the one-piece vs. two-piece, pad thickness, and bridge are the main differences. They are far more similar than different, and one certainly can't obtain a brake system that is any closer to the design of the RSR brakes than the one we're offering.

Disc material choice in racing is defined by the rule set. Carbon-carbon is used when budget isn't of much concern, and iron is the clear choice when the series is trying to keep prices out of the stratosphere. The carbon brakes currently being used in professional racing are carbon/carbon (abbreviated C/C), which is actually a different material vs. the carbon ceramic discs used on road cars. The carbon ceramic brake discs on road cars are a Carbon Ceramic Matrix (CCM). In recent times many professional racing series (F1, ALMS, IRL, etc.) have switched to carbon/carbon brake discs in an effort to reduce weight. Carbon/Carbon is an outstanding lightweight material for racing, but requires heat before it starts to generate usable friction. As such, they're completely ill-suited to a typical morning commute in a road car!

In our opinion carbon ceramic discs (which is what PCCB discs are) are not well-suited for racetrack use. There is no doubt in my mind that alternative materials are the future of brake disc design. Based on all of our testing however, carbon ceramic discs in their current state of development cannot perform at the same level and offer all of the benefits of iron discs. Even though their development has come a long way, they still have a laundry list of pitfalls when taken on the track. The biggest problem is that they tend to oxidize at track temperatures, showing rough surface eruptions on the disc face. They also tend to run considerably hotter than iron when all else is held equal, they are horribly expensive to replace or resurface, they can only be run with an expensive and limited range of pads, they have poor feel, and they are more damage-prone than iron.

Personally, I have no idea why anyone tracking their car would want carbon ceramic discs. While I was working at StopTech over ten years ago, we tested continuous strand carbon ceramic discs on my C5 Z06 from an aftermarket manufacturer that is currently being touted on this forum. I destroyed them in a single afternoon at Buttonwillow. We therefore decided not to offer them to our customers as a viable, track-capable solution, because they weren't. Ever since, I have been extremely skeptical of the CCM technology for racetrack use. Based on what we see in other markets, that situation hasn't changed. The newer discs are better, but still not on par with iron for track use. We see it in a slew of other markets...Ferrari, Lambo, Corvette, Camaro, BMW M, Audi RS, etc. The very first thing our exotic fleet customers do when they obtain a new car is convert the carbon ceramic discs to AP Racing iron, and save themselves a small fortune in the process.

I think the problem with the "buying the best" concept is that people are misguided. They simply don't know any better, and frankly, it's really not their fault. The manufacturer does everything possible to align their road car with their race cars, and they sell carbon ceramic as 'race-derived technology.' The person sees carbon-carbon discs on the racecar variant of their chassis, and they believe it's the same thing that is on their car, and that it's the best possible option. Unfortunately, it's not.

Iron discs have been proven over and over for decades to be capable of winning races like Le Mans. They just did it again, so why would you need or want anything different? The key benefits of carbon ceramic discs are 1) unsprung weight savings, and 2) that they last for an incredibly long time when driven around on the street. They are inferior in just about every other way for how our customers actually use them...as noted above, they cost more, they run hotter, they're more fragile, offer less pad compatibility, etc. Since our iron system offers a similar weight savings as carbon ceramic discs mated to stock calipers, there is no significant weight advantage to the carbon ceramics. If you're planning to track the car, then the 'lasting forever on the street' benefit is essentially meaningless as well. Therefore, iron makes a whole lot of sense.

If you want cutting-edge technology and exclusivity, the Radi-CAL is far more in that vein than CCM discs. No other manufacturer offers a similar caliper, and they are truly race-proven parts, not 'race-inspired.' We're offering something that is incredibly similar to what just won Le Mans, and the Radi-CAL owner club is far more exclusive than the carbon ceramic club these days. Every major manufacturer seems to be offering carbon ceramics on their road cars. I think I saw a Kia with them on my lunch break yesterday!

JRitt@essex

Shandingo,
You are correct in just about all cases until very recently. The particular caliper in question actually has a removable bridge, whereas most of AP's elite-level racing calipers of the past were machined from billet with a fixed bridge. The billet ones are even lighter yet, but they are more like 3-4 times more expensive, rather than merely double!

JRitt@essex

Below is a shot of the RSR front caliper. The two little bridge pieces pop out, leaving just the spring clip which functions as shown in the pics above. One of our race guys snapped some pics at the track earlier this year as well. I'll see if I can dig them up.