Petevb

In addition to the slightly better turn-in PCCBs will offer slightly better grip due to the decreased unsprung mass allowing the suspension to work better. Not easy to feel, but it's there.
You missed this quote from automobile, Porsche will now offer OEM steel replacement rotors for the new 991 GT3 PCCBs:

"The high cost of PCCB pad and rotor replacement is a matter of consideration for a small number of Porsche owners. Due to this, Porsche offers a unique steel rotor and a brake pad setup for PCCB-optioned cars, available through the parts department at Porsche dealerships. Owners can then fit this steel setup to their GT3 for track days, helping keep the costs of wear items in check."

Read more: http://www.automobilemag.com/reviews...#ixzz2aY5XhwOa

Given this new option I'd be highly inclined to check the PCCB box if I could afford it.

orthojoe

Interesting that they would account for track use, but then why bother to option with PCCB if you are going to track extensively?

Petevb

If you're only going to track then the advantage might be the bigger 410mm rotors, presumably they would hold up better than the standard 380mm steels. Personally I autocross as well (and street drive), and the PCCBs are an advantage against the clock at the AX. The question is simply if that's worth the extra $$.

Nick

Sorry,they can tried to sell this dog but it will not hunt. Porsche OEM brakes are fantastic and the need for PCCB's are dubious at best. What gets me is they could reduce the price of PCCB's by at least the cost of the standard brakes but apparently have not. I have to believe this is a huge profit margin for Porsche.

Dan39

PCCBs are not practical for the track full stop. I doubt the steel brakes can withstand 6 x 30 minute sessions of hard driving either, though. I'm fully expecting I'll have to start with upgraded fluid and then upgrade the rotors and calipers when they get worn and warp after 3-5 track days in Year 1.

On the street, you can certainly feel the difference of shaving 5kg per corner - it's about the difference between the normal and super light rims I installed on another car. You can feel it and it lightens the steering but to say you get better grip and braking from such a small difference is theory not reality.

Petevb

First, fyi lightening rims will have a bigger effect than lightening brakes due to the location of the mass. The rim has mass at a larger distance from the point of rotation, giving it larger gyroscopic effect. Hence taking off 5 kg from the rim will be easier to perceive than taking 5kg off the rotor on turn-in, etc.

Second, a suspension's ability to follow the road and grip is very effected by the ratio of sprung to unsprung mass. Especially on the front end of a 911, which is relatively light and has large heavy brakes and wheels, that ratio is changed significantly by 5kg. While I don't doubt you won't notice the difference, grip over a bumpy corner is unquestionably effected. I agree you'd likely need data capture or a stopwatch to tell, or perhaps drive the two cars through the same corner back to back.

Dan39

Interesting point re the masses and gyroscopic effect. However, I think we agree that for 99.9% of the people buying these cars it is a distinction without a difference, i.e., they could not tell the difference back to back between -5 kg of rim weight and -5kg of brake weight.

Petevb

It's about 2x the effect on the rim vs the brake disk. So if you can tell on the rim it should be about half as obvious on the brake disk.

As an aside there are race series where wheel weight is limited by the rules. In these cases they good wheel manufactures make the lightest wheel they can, then they put the weight back in the center of the hub to make weight. Might not make a big difference, but everything helps.

reidry

The spring rate and dampers are tuned to provide a balance between the two factory options the Steel (380mm Front / 380mm Rear) and the PCCBs (410mm Front / 380mm Rear) and we expect the mass of the PCCB components to be slightly lighter per corner even with the added diameter.

Buying the special steel rotors through Porsche parts will add a minimum of 7 lbs per corner beyond the weight of the base steels - likely the total system weight goes up even more as the hat may need to be stiffer and the PCCB caliper bracket may be heavier than the base unit as the caliper is further from the spindle. How was that factored into the suspension tuning and steering calibration?

I'm still going with the base steels.

Ryan

911rox

If you upgrade to a racing fluid, the stock steel brakes work fine accept for the fact that they will crack eventually. I run SRF, upgraded to PFC dimpled rotors (to address cracking) and have never looked back... I've run 8x30min sessions in 35oC heat with no fade or probs and that's on stock pads... Stock brakes are that good so no need to waste money on calipers... Pads, rotors and fluid- you're done. Current rotors have 3000 track kms on them, no warping, no cracking accept for surface crazing... I'm now running within 1 sec of my pro drivers' times so they're not sight seeing laps either...

Dan39

Great post, very useful. Will do the fluid right away and then make a decision on the pads and rotors when they're done.

reidry

Great advise

For everyone considering a little track time replacing the factory brake fluid with a racing fluid should be accomplished before the first track session.

An interesting note, I alternate between ATL Super Blue (Blue in Color) and Typ 200 (Translucent Amber in Color) in my track car, but the state of Florida has specific law requiring clear or yellow brake fluid for all cars on the street.

Ryan

Dan39

Interesting, why not the Castrol fluid?

Manifold

My experience has been similar. Stock rotors with holes crack too soon with heavy track use, so I switched to PFC dimpled floating rotors; they also eventually crack (crazing pattern), but last longer and are worth it. I use Prospeed RS683 brake fluid. But I wouldn't consider using stock pads, I use PFC track pads on both track and street; they have much better bite and last much longer than the stock pads.

reidry

Keep in mind my dedicated track car is a Spec Miata which is pretty easy on brakes compared to a full interior Porsche. When alternating between the blue and amber fluid it is easy for me to tell when I have completely purged the line to a caliper.

The Castrol SRF product does have a slightly higher dry boiling point and a much higher wet boiling point. It is also more expensive. For the Miata I tend to over-service all the fluids so the wet boiling point doesn't come into play.

Here is a link to a comparison table containing wet and dry boilding points for a number of popular high performance brake fluids:

https://www.pegasusautoracing.com/gr...pID=BRAKEFLUID

Ryan