WHT

Regarding Corvette Calipers:



Regarding AP CP6077 Calipers:



Regarding W6A Calipers:


The W6A is a 6 piston caliper with 28.5 mm / 28.5 mm / 41.1 mm pistons



Johnny, based on you engineering knowledge, to help us buy calipers, what are good/proper piston diameters for a 6-piston Corvette caliper?

johnny c

Yes sir, if you slap on a set of burnished pads and “go” as you put it you will have zero brakes. The corner entry speed for turn 1 @ road Atlanta is 113 mph. with zero brakes you will find the wall at 90mph. if your taking out your track day toy and find a wall @90mph you have a very slim chance at survival. That impact will be near to 80-90G. even in a filly prepped car that would be hard to walk away from.

As I and Jeff @ essex has said. pre bedded pads is nothing without a rotor that is also pre beaded. When beading brakes your attempting to apply a material called a “transfer layer”. A transfer layer will look like a blue-ish tint on the rotor. That tint is pad material, that material interacts with the pad compound and increases the coefficient of friction. Without that transfer layer your pads will work at a greatly reduced capacity. When I was @ PFC and we sold pre beaded pads, they were intended to go with a rotor that was also pre beaded. For example @ the 24 of Daytona before carbon carbon rotors. Hour 12-15 the teams would need to swap pads. They ordered pre-beaded pads, the car would come into the pits, while hot, they would remove the old pads, slap in the pre beaded pads, and head back out to finish the race. With the pre beaded pads the car’s braking would be unaffected. That was the main reason for pre beading.
I need to put a statement out there that your recommendation is dangerous. Braking is a part of the safety component. This isn’t camshafts , if we get it wrong people can die.

johnny c

I’m sorry I should explain the tiny piston comment.
It was in reflection to my pro touring customers. These guys are using C5/c6 spindles. So naturally they pick up off the shelf corvette brake kits. The wildwood unit is cheap so I see it a lot. The problem is.. That most of these guys have a 1960ish 3800lbs-ish car, a 60% front weight bias, and a center of gravity that’s 24”high . BUT!! They have the brakes for a car with 3000lbs, a 50/50 weight bias and a 17” center of gravity. Most of them have manual brakes and need double the piston size. Running manual brakes (VS boosted) needs a much larger piston. So they call me, I see that kit, and almost every time need to throw it away. That being said I am not a fan of wildwood at all. I had wildwood calipers on my car until one event when the caliper developed a burr where the pad sits. That burr held the pad to the rotor and caused a ton of drag. That drag super-heated my fluid and vaporized it. I went into turn 3@ cmp with ZERO brakes. If it was a faster turn my car and possibly myself would have been toast. I’ve never seen a caliper built that poorly before, and it was supposed to be a “FORGED” caliper. For everyone to understand a burr should not form where the pad sits. That is ****-poor material selection at work. After that I cannot recommend anyone to run their calipers out of safety concerns. I replaced the willywoods with a AFCO caliper and have been very impressed with the performance so far. I'm still testing them to destruction currently but 2 events in and they are doing well.

johnny c

I love your questions fat billy, keep them coming
This is the difference between a pad that has a bead in procedure and one that does not. An Achilles heal of carbotechs is that they need to be beaded in. this bead in process is to try and obtain a transfer layer. (posted before: a transfer layer is a blueish tint on the rotor, that tint is pad material. It greatly increases the coefficient of friction). Carbotechs have been known to lose its transfer layer mid race, or have a hard time obtaining it. Thus a bead in procedure is required to try to get the transfer layer.

The difference is

With a Professional level pad like a PFC/Padgid there is no bead in procedure. As long as your rotors are free of impurities they will get a transfer layer on the way into your first turn. I personally have experienced this. I’m a NASA TT racer. I’ve slapped on a fresh set of pfc 01, and flew into turn one. All those pads need to get and keep a transfer layer is to be hot.

We don’t see that in modern pads, with any manufacture. This thermal shock of them becoming heated too quickly. What I do see is the ABS killing a set of pads. A pad (and rotor) will come up to its thermal limit, then the abs plays patty cake on it. That’s never good.

Mario Andretti called the PFC 01 compound turn 1 ready. As far as I’m concerned the greatest racer to ever live. That’s who I’m quoting. Yes you do have some time to check the brakes out and I hope everyone does, and then listens to them. A lot of people get wrapped up in the moment and hopw the proplem goes away during the run. Sometimes it does, sometimes it gets worse. Heck sometime brake failure is sudden and unexpected. I posted a story about myself @ cmp in a previous post. Went into turn 3 with no brakes, no warning. Lucky to find some not wet grass lol.

]
like me and Jeff has said before it's a pro level move. the idea is that you get pre-beaded pads to go on to pre-beaded rotors. that way when you leave the pits your brakes "feel" won't change. this is very important to mid race pad changes. or when you have a track rented for testing and every lap is expensive. it does little for your average club racer.

johnny c

your going to want the 7751 pad shape. lots of compounds available for it. what tires are you running, i'll recommend a compound.

CONTACT KNS BRAKES FOR ORDERING.

johnny c

I would like to see that car on PFC 11's if you still have a booster. if your running manual brakes i would like to see the 05's or 13's.

CONTACT KNS BRAKES FOR ORDERING.

z06801

Does PFC make a that pad for a Brembo GT 265mm kit and a front c5 z06 caliper which is on my rear? C5 Z06

3on8

Johnny - I'm confused...
Can I put fresh -44 PFCs on fresh, virgin rotors that don't have a transfer layer, and be "Turn 1 ready?"

johnny c

as long as there is no contamination on the rotors all you got to do is get them hot. you can go into turn 1 hot and that's all you need to get a transfer layer.

It's advisable you brake early for that first turn. just to be sure you don't have contamination on your rotors.

3on8

PFC shape number for stock C5z06 front is 0731. Full part number will depend on compound you pick.

johnny c

i need to know what caliper that kit uses and i'll find you a pad shape. also tell me what tires you have, and i'll recommend a compound.

z06801

thanks I'll see if I can find it, I know its the same shape as my friends GT-R just shorter by a few mm

z06801

Thanks

3on8

Thank you, Johnny.

Poor-sha

So I have a question. What causes those grooves in a rotor that look (and feel) like someone ground the pads down the backing plate and kept going? I've seen those on rotors that have never seen a worn out pad. Is it an inconsistent pad material from bedding?

edge04

what should one do to the rotors if they do have to run different brake compounds on the same rotors. Would you just go through a normal bedding process? I recently switched from Ferodo's to Hawks and bedded them in on track during a warm up session and didn't notice anything out of sorts.

johnny c

do you have a picture? i'm not 100% sure what your describing.

johnny c

you didn't notice that you had significantly less TQ in your system while beading.

edge04

I don't bead them in from any speeds higher than 70 or so. So hard to tell. But sounds like you are saying that the beading process is the answer

0Todd TCE

I agree with your position on piston area with regard to manual brakes Johnny, yes! And for the most part when I personally deal with that or a drum rear, or drum to disc conversion take that all into account knowing they are going to need to properly pair that design to their current mc. But..for the majority of Corvette owners that's not what they are running. *I'm sure some run dual mc's pedal kits and such but not everyone, most buying for the stock mc and booster.

I won't get into the Wiwood debate I respect your choices, but the you are making a bit of blanket statement (the pistons are flipping tiny) that is a bit tilted- to your reference of manual brakes and distaste for the brand. Saying the pistons are too small is not quite true when the piston area of most kits are all in the 4.0sq" ballpark. Again, not picking brands here just asking that the complete info be put up. Rather than simple caliper brand references- a listing of the piston areas of the varying brands might be a more complete approach.

FWIW:
2 piston Corvette 3.99" (per centric)
6 piston Corvette 3.97 (per centric)
4 piston AP 3.84 (per part number from promo literature)
6 piston AP 3.84 (per part number from promo literature)
6 piston Wilwood 4.06
-Stoptech
-Brembo
-Others

Doesn't appear to be any less than the others.


*I don't know what recommendations I gave that are dangerous, but if I did I apologize. I feel my pad thoughts err on the side of being more conservative actually.