Originally Posted by TomTarzian

Took the words out of my mouth...err, fingers. There is nothing in the least squishy about them. They are sublime at all times. The Porsche version doesn't even suffer in the rain, unlike CCB's I had on a BMW F10 M5, which were dangerous in the rain for the first few stops.

God bless,
TT

Originally Posted by Gatch

Pardon my ignorance, and please don't yell at me Archimedes , but with the Spyder now sporting GT3 brakes as standard (or maybe just at the front?), it seems that by paying for the PCCB upgrade, you're paying for brakes twice. Clearly there are passionate folks on both sides of the argument, but it was a no-brainer when I ordered my 718 Spyder...the "stock" brakes, just like most aspects of the 718 GT4/Spyder, are more than enough for street use. Now if there really is a GT4RS coming, that'll likely come standard with the PCCBs and that would be entirely appropriate.

I think the more reasonable question is...why is Porsche charging $900 to paint the calipers black?! That should be a no-cost option. And I'm sure it will be down the road.

Originally Posted by wizee

Both the steels and PCCB are more than enough brake for the car on the GT4/Spyder, in terms of stopping power, heat capacity, and heat dissipation. PCCB can dissipate more heat by virtue of higher operating temperatures and more surface area, but the steel GT3 brakes are more than enough. The useful reasons to get PCCB on the GT4/Spyder are:

• No brake dust or rust
• Saves about 10 lbs/corner unsprung mass, significantly improving tire contact over rough pavement
• Saves 40 lbs overall from the mass of the car
• Better brake pedal feel
• They look cool

Originally Posted by wizee

Both the steels and PCCB are more than enough brake for the car on the GT4/Spyder, in terms of stopping power, heat capacity, and heat dissipation. PCCB can dissipate more heat by virtue of higher operating temperatures and more surface area, but the steel GT3 brakes are more than enough. The useful reasons to get PCCB on the GT4/Spyder are:

• No brake dust or rust
• Saves about 10 lbs/corner unsprung mass, significantly improving tire contact over rough pavement
• Saves 40 lbs overall from the mass of the car
• Better brake pedal feel
• They look cool

Originally Posted by hf1

Is the disk weight diff really 10lb? Do you have a reference for this info? On some other cars I’ve read it’s more like 5lb weight saved per disk.

On brake pedal feel, I’ve read that CC brakes are more grabby, more on/off, and harder to modulate than irons. Is this not the case with PCCB? Quite possible that Porsche excels here as well.

Originally Posted by wizee

The huge GT3 steel brake rotors are heavy. See this thread and post: https://rennlist.com/forums/991-gt3-...l#post12895243

Originally Posted by RyuBraska

Any tip on how to do that other than breaking hard AF?

Originally Posted by hf1

Is the disk weight diff really 10lb? Do you have a reference for this info? On some other cars I’ve read it’s more like 5lb weight saved per disk.

On brake pedal feel, I’ve read that CC brakes are more grabby, more on/off, and harder to modulate than irons. Is this not the case with PCCB? Quite possible that Porsche excels here as well.

Originally Posted by frosty911

Is it true that carbon ceramic brake don’t bite as fast when wet as an equally wet iron rotor. For example, you’re driving on the highway and it’s raining hard. You need to do a hard deceleration. The ccb brakes won’t bite as fast As iron ones. That’s something that seemed to happen with the ccb brakes on the new m5 f90. Some people have said (on the forums) that it was actually scary sometimes to get a delay in brake response with the ccb when they were wet. Now that was on a bmw m5. Is it the same thing on porsches?

Originally Posted by Archimedes

Sorry but this is one of the dumbest things I’ve ever read on Rennlist, and that’s saying something. Have you ever owned, or even driven, a car with PCCBs? There is nothing squishy about them, not even dead cold on the first stop.

Had to delete the rest of your post of nonsense. You’re parroting stuff that you’ve read one the interwebs, and not even getting that right.

Originally Posted by Pokerhobo

You have much more experience with PCCB than I do, but I have read about them being squishy when not up to operating temperature and that carbon ceramic brakes have a higher minimum operating temperature than steelies. Unfortunately, I wasn't able to find any concrete information as all hits only say that carbon ceramics have a much higher maximum operating temperature. I did find this: https://www.autoguide.com/auto-news/...ic-brakes.html that talks about carbon ceramics being squishy when cold compared to steelies...

Originally Posted by mrsullivan

This has already been beaten to death. 40lbs of rotating mass at the wheels is very different than 15lbs of seat or battery. So you cannot run a linear equation there = horsepower, etc. Its not as simple as that. Or losing a little weight. I have owned GT3s with and without the PCCB. I suggest that the 40lbs of rotating mass is detectable in terms of handling characteristics, but I would have bought just for the look and lack of dust. To me its also a mental thing. If I am spending the extra $ to have Porsche top performance model, shouldn't I spend a bit extra to have the lightest/highest performing spec. Even if its not about laptimes or track.

Originally Posted by Gatch

Originally Posted by Petevb

It is quite surprising the way it works out. In terms of moment of inertia, which changes turn-in, acceleration, etc, the position of the mass matters more than the quantity, which leads to some surprising results when you look at the wheel and tire package as a system:

First realize that rubber is surprisingly heavy, and it's located way out at the edge of the wheel. Shaving 1/8" of rubber works out to roughly 4 lbs on our width tires, but since it's out at the edge of the wheel as opposed to close to the center, this difference has an outsized effect on moment of inertia (MOI). That 4 lbs is roughly equal, in fact, to the MOI of the entire 14.8 lb PCCB brake disk, meaning it's just as hard to accelerate, turn, etc.

This has a different effect than simple unsprung weight which effects ride, of course, but the flywheel effect on turn-in is often described as being the most noticeable difference for PCCBs- the ease with which the wheel turns.

In terms of this the iron rotors do have a 37% higher MOI than PCCB, but that's only equivalent to roughly 1 mm more tread rubber- not exactly a big difference when viewed this way.

If we then simply focus on "unsprung weight" the difference is also much smaller than first appears. One must keep in mind that the iron rotors lose nearly 2.5 lbs before they hit the wear limit, while PCCBs do not lose nearly as much. Thus looking at the front, worn iron rotors and pads with a shaved tire will cut the absolute weight difference to PCCBs to zero (4 lbs of shaved rubber, 2.5 lbs of lost rotor mass, 1.5 lbs for worn pads, while the calipers and pads were 1 lb lighter to begin with = 9 lbs, where the stock PCCB rotor is ~9 lbs lighter to begin with). This setup will also have a nearly 40% lower moment of inertia than the PCCB setup with fresh rubber, so in virtually every way could be expected to perform better.

I don't find it impossible to believe that some people could tell the difference with PCCBs, and in absolute terms they should be fractionally faster when all else is equal. The difference you're trying to feel, however, is in most ways smaller than fresh vs shaved rubber, particularly with worn vs new rotors and pads. In other words it's really quite small, and in the real world dwarfed for me by other effects such as brake feel, etc.

Throw in the added front downforce the iron rotor generates on the GT4 and I do start to wonder which car would be ultimate faster on fast tracks over a single lap, a worn iron rotor car or a PCCB car...

Where the PCCBs still retain a big advantage is in absolute braking capacity. A 918 equipped with the GT4's iron rotors could dump enough power into them to overheat and fade them. The PCCBs on the other hand have more surface area to shed heat, as well as a higher allowable peak operating temperature. This means you can push them harder before they give up. The GT4, however, has less than half the 918's engine power- likely not enough to practically be able to overheat the standard metal disks. They are after all the same dimensions as you'll find on many cars at Le Mans, so in this instance the PCCB's thermal advantage is somewhat academic. On a 918 however it's clearly not.

Food for thought as you decide how to spend your $$.