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Please check out our latest blog post that contains a LOT more info on the AP Racing Radi-CAL design. It's worth your time if you're at all interested in the technology that goes into brake systems at the pinnacle of motorsport. The AP Racing Radi-CAL Story
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'09 Carrera 2S, '08 Boxster LE (orange), '91 Acura NSX, Tesla Model 3 Performance, Fiesta ST
Jeff Ritter
Mgr. High Performance Division, Essex Parts Services Essex Designed AP Racing Radi-CAL Competition Brake Kits & 2-piece J Hook Discs Ferodo Racing Brake Pads Spiegler Stainless Steel Brake Lines
704-824-6030 jeff.ritter@essexparts.com
Prospective GT3 owners have been calling and emailing us with the same anxiety & concern:
I've got a 991 GT3 (RS) coming in Sept 2015 and am debating between irons and PCCB for the build. Will you be offering iron replacement kit for stock PCCB?
Our advice is always: If the extra some $8k pccb option is not an issue, then you should take that option and enjoy the newest brake technology with ease, and consider aftermarket Iron Rotor Replacement later on if it becomes necessary.
I am sure you have been reading all the benefits of pccb for its light weight, no dust, and last forever (street driving) witnessed by pccb owners.
So if you don't track, pccb is the way to go - You want your 991 to show off its beauty with the massive brake (410mm CCM rotor w/yellow calipers) behind the wheels to enhance the value of your investment because it's a Porsche.
Even if you will track your GT3, things may not be that bad at all compare to what you have learned in the past, although some claimed improvement yet to be proven:
pccb rotors are now into 3rd generation, and they are more durable.
Aftermarket replacement CCM has become more available and affordable
Iron rotor replacement is readily available
Replacement to factory pccb set up; pad, rotor, or even calipers can be "progressively" replaced/upgraded as you feel need - To preserve your factory pccb while experiencing what's out there from aftermarket other than factory set up, to make your motorsports more adventuresome
This idea is how RB brakes for 991 GT3 were developed. Not only we offer both CCM (ST & ZR1 discs), and Iron rotor replacement. We even offer stock caliper replacement with a direct bolt on installation, for those who want something better than stock, while retain the use your OE rotors like we offer tor Nissan GT-R.
We also offer brake pads for both street and track. Except CCM track pads to be released in 6-8 wks.
If you like Pagid or PFC stay with them, but if you like to try something different you may want to give us a try. For example to go with pccb Iron rotor replacement, we make that pad with XR70 track compound for "Iron rotor" conversion, vs. OE pad which is made for CCM rotors.
Just take a look on our complete offer for your GT3 brake option and just keep us in mind for your future need while enjoying your pccb.
And if you are to track your GT3 heavily and frequestly, you should consider our complete brake kit (RB calipers w/rotors built with ZR1/Z28 CCM discs).
This set up will make you "Porsche Brakes" to have compatible CCM discs and pads as ZR1/Z28 and other owners (like GT-R and other CCM retrofit*), for a much lower cost and easy availability on disc and pad replacement compare to running factory "pccb".
For your information:
Porsche 992 GT3 Front: 410x36 Rear: 390x32
RB offers the same retrofit kits for Ferrari (F430 & F458) and McLaren MP4, which all have the same factory brake pads. So this set up has, without a doubt" become the standard rotor and pad of CCM brakes.
Very affordable for the complete kit with easy and low maintenance cost down the road:
We're looking into possibly developing a complete caliper & disc kit using AP Racing's latest Radi-CAL technology. “Radi-CAL” is a blanket term used to describe AP Racing’s patented asymmetrical brake caliper design. Radi-CAL technology is grounded in Computer Aided Design (CAD) and Finite Element Analysis (FEA), and allows for organic, alien-looking designs that are a radical departure from conventional caliper designs of the past. Calipers leveraging the Radi-CAL design philosophy are widely considered the pinnacle of current brake caliper technology. Since their inception in 2007, these revolutionary calipers have amassed a lengthy string of race victories at all levels of professional motorsport, while redefining brake performance expectations.
Having pads held by springs like the 930 calipers on my 911 is sooooo easy to work with compared to having to remove calipers or even just deal with those pins that have to be hammered in and out (and the invevitable wear to the caliper finish).
Such a shame that the GT3/GT4 calipers are not made this way, but thanks for considering the production of these. Wish they weren't $9k, but the thicker pads will last much longer and if one does lots of tracking, it will save many headaches over the years!
So I guess Porsche decided to use "the have to remove your calipers" to make pad changes. This is obvious in order to boost dealer service dept revenue.
I'm fairly sure the caliper design change was actually done to improve pedal feel. The one piece bridge is almost certainly going to lead to less caliper flex and hence a better pedal feel.
Most owners won't be particularly bothered by the more difficult pad swaps- ask yourself how many brake pad swaps the average 918 owner is going to do in 5 years? High mileage track rats are still a relatively corner case, at which point it comes down to a cost vs performance tradeoff, like everything else. So I don't see conspiracy here. Unlike replacement PCCB disk prices which I'm rather sure are rigged.
I'm fairly sure the caliper design change was actually done to improve pedal feel. The one piece bridge is almost certainly going to lead to less caliper flex and hence a better pedal feel.
Pete - Wouldn't something like this (made by Brembo like OEM calipers) achieve both results without having to remove calipers for pad changes?:
Please check out our latest blog post that contains a LOT more info on the AP Racing Radi-CAL design. It's worth your time if you're at all interested in the technology that goes into brake systems at the pinnacle of motorsport. The AP Racing Radi-CAL Story
Some interesting stuff there, Jeff! Looks very nice.
I'm fairly sure the caliper design change was actually done to improve pedal feel. The one piece bridge is almost certainly going to lead to less caliper flex and hence a better pedal feel.
That is the party line from Porsche. However 2 things I'd like to point out:
1) nobody complained about pedal feel with the older design. Brake edal feel was never a problem with the GT cars. I'm going to guess there isn't a big difference in feel between 997 and 991.
2) Pad tapering was a problem on the 997, so one thought was that the fixed bridge would stop the problem. However, with stock pads, the 991 pad have been reported to taper still. I never had problems with pad tapering on 996 GT3 calipers and 991 GT3 calipers using aftermarket track pads.
I haven't seen any benefit, from my standpoint, with the new caliper design.
That is the party line from Porsche. However 2 things I'd like to point out:
1) nobody complained about pedal feel with the older design. Brake edal feel was never a problem with the GT cars. I'm going to guess there isn't a big difference in feel between 997 and 991.
2) Pad tapering was a problem on the 997, so one thought was that the fixed bridge would stop the problem. However, with stock pads, the 991 pad have been reported to taper still. I never had problems with pad tapering on 996 GT3 calipers and 991 GT3 calipers using aftermarket track pads.
I haven't seen any benefit, from my standpoint, with the new caliper design.
That may well be, but that doesn't mean the new caliper design isn't helping indirectly.
Keep in mind that the new pads are significantly larger that the old- nearly 1 cm both wider and taller for PCCBs. If you imagine that the caliper needs to support load like a bridge, you've just built a significantly larger bridge. You'll need a stiffer caliper just to maintain the old pedal feel.
The question then becomes pad size- do you need the bigger pad? That probably depends, but it should wear a little better, be a bit more fade resistant, and critically be a bit more friendly towards the PCCBs. My suspicion is that the engineers followed a chain of logic along these lines. I don't think they'd go to the trouble otherwise, and I don't think they're simply blowing smoke. But I've been wrong before...
That may well be, but that doesn't mean the new caliper design isn't helping indirectly.
Keep in mind that the new pads are significantly larger that the old- nearly 1 cm both wider and taller for PCCBs. If you imagine that the caliper needs to support load like a bridge, you've just built a significantly larger bridge. You'll need a stiffer caliper just to maintain the old pedal feel.
The question then becomes pad size- do you need the bigger pad? That probably depends, but it should wear a little better, be a bit more fade resistant, and critically be a bit more friendly towards the PCCBs. My suspicion is that the engineers followed a chain of logic along these lines. I don't think they'd go to the trouble otherwise, and I don't think they're simply blowing smoke. But I've been wrong before...
I know what you're saying, but how do we explain why Porsche is using the new new closed top/bridge on ALL of their calipers, including the small 4 pots on the caymans and boxsters?
It's all about "lowering" the mfg cost, then marking up its "advantage" through marketing.
OE calipers are "casted", the 'center bridge' makes the molten aluminum easy to flow across and fill up the cavity.
Casting aluminum has the lowest density (strength) among extrusion (short run monoblock machining) and forging (two halves).
Two halves calipers are stiffer and stronger, because they are assembled with alloyed steel bolts to reinforce the soft aluminum body.
Do you have any FEA or data to support this claim?
Stiffness and strength are two very different things. I have no doubt your alloy steel bolt across the caliper is far stronger than the cast bridge Brembo uses. However the complex casting cross section is about twice as thick as the bolt shown. Bending stiffness goes to the cube of thickness, meaning if that's the geometry even cast aluminum would be far stiffer in bending than alloy steel, and that's before considering any play in the bolted connection.
I see no data in the link you posted. If you have material properties or other data that you believe proves your case let's hear it.
You seem to be arguing that Porsche chose to compromise the braking performance of their $1M 918 to save a few $ per corner, and that the older technology they discarded in the process actually performs better despite appearances. I'd need convincing in the form of data to believe that...
04-17-2015, 01:10 PM
