Cryo Treatment Tech

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Vincent Keene wrote:

MikeWhitney wrote:

You could probably stop the car fine with paper towels stuffed in there for brake pads. IMO XP8s are overkill and ducting is probably overkill in that setup.

The stock setup did "OK" until I warped a set of Panther Plus pads down to plates in one weekend at VIR-S. The single piston caliper did them in. That when I decided I needed better brakes.

Don't get me wrong, I'm jealous (and I meant paper towels with the big brake setup)

I totally understand that the stock brakes were undersized, and I'm sure the BBK was a great idea. The nice thing about BBKs, as I akways understood it, is that with bigger brakes a person doesn't have ot run aggressive pads, or ducting, and generally wear rates should go down!

Vincent Keene wrote:

MikeWhitney wrote:

I bet the XP8s are killing the rotors - you need a more rotor friendly pad. Me myself I was never a fan of Carbotechs. All the sets I tried ruined my rotors and turned into potato chips.

So what pad would you recommend? Just to be clear the rotors have never warped, just heat checks like mad.

Hmm, I'm not sure. I have run the PFC-Zs in the past and I understanfd about the bad initial grab thing. I'd really recommend calling our new sponsor and give them this challenge, see what they would recommend.

FYI the "potato chips" comment was about the Carbotech PADS themselves -- I severely bent the backing plate on every set I tried. Never had that problem with Hawks or PFCs.

I ran PFC 90's on my E30 on track and was really really pleased with how rotor friendly they were ... just a data point. You might even want to try something like a Hawk HP+ or even (gasp) an Axxis Ultimate. It all sorta depends on how hot you're getting the rotors.

One weekend a few years back Matt N had some "temp paint" -- different colors he painted on the outer edge of the rotors that would turn to white if the temp point was exceeded. I turned all 3 of them white - highest temp was maybe 1200F?

Pad/rotor metallurgy is actually pretty complicated. There are a number of intermediate compounds which form, some you want, some you don't. I just wouldn't be surprised if you're not getting the XP8s up to a reasonable temp this could be contributing to your problems, and if you're cooling the brakes *too quickly* with the ducting it could be contributing as well.

Only some experimentation will tell.

Vincent Keene wrote:

MikeWhitney wrote:

I think you should get the rotors turned, use a less aggressive pad, and bring an IR gun to the track on to make sure you are getting *enough* heat into the rotors.

What good would turning a non-warped rotor do? Just to remove the residue from the pads? How much heat is enough? Should I ditch the ducting?

If the heat cracks are what I am suspecting, they are probably pretty shallow, and turning them will remove them, and the stress points they either grew from and/or created. It will also get rid of the pad materials, compounds, and other oddities that the XP8s probably left there which caused the cracking in the first place.

It's an interesting problme...

Vincent Keene · **Posted:** Wed Jan 31, 2007 1:39 pm

MikeWhitney wrote:

The nice thing about BBKs, as I akways understood it, is that with bigger brakes a person doesn't have ot run aggressive pads, or ducting, and generally wear rates should go down!

My thinking as well, but it hasn't worked that way so far.

MikeWhitney wrote:

I have run the PFC-Zs in the past and I understanfd about the bad initial grab thing. I'd really recommend calling our new sponsor and give them this challenge, see what they would recommend.

I still have the PFC-Z pads I started with when I first tried the BBK at Rockingham. The lack of the inital bite was my only complaint with them.

MikeWhitney wrote:

I ran PFC 90's on my E30 on track and was really really pleased with how rotor friendly they were ... just a data point. You might even want to try something like a Hawk HP+ or even (gasp) an Axxis Ultimate. It all sorta depends on how hot you're getting the rotors.

I just wouldn't be surprised if you're not getting the XP8s up to a reasonable temp this could be contributing to your problems, and if you're cooling the brakes *too quickly* with the ducting it could be contributing as well.

I think you should get the rotors turned, use a less aggressive pad, and bring an IR gun to the track on to make sure you are getting *enough* heat into the rotors.[/quote]

BTW, who sells the other PFC compounds? Seems like a saw a good price on the D412s in their 80 compound somewhere. On the Hawks, do you think I should try the HPS or step up to the HP Plus?

Vincent Keene · **Posted:** Wed Jan 31, 2007 1:45 pm

I found this when looking for the temp paint.

Quote:

Refer to the table below as a guide for determining optimum brake pad compound selection:
Maximum
Temperature (F) Pad Compound Selection Guide*

Up to 750F Most Semi-Metallic Street Pads including:

- Ferodo DS2500
- Hawk HPS
- Hawk HP Plus
- Hawk DTC-05
- PFC Carbon Metallic
- PFC Z-Rated
- Rofren Ultima Street
- Rofren Euro-Select
- Rofren Street Performance

750F -
1000F Street Performance / Limited Track
use pads including:

- Ferodo DS2500
- Ferodo 4003
- Hawk HP Plus
- Hawk Black
- Hawk DTC-30
- Hawk DR-97
- PFC Z-Rated
- Rofren Street Performance
- Raybestos ST-38
- Raybestos ST-43

1000F -1250F Intermediate Race Pads including:

- Ferodo DS3000
- Ferodo DS1-11
- Hawk Blue 9012
- Hawk MT4 Blue
- Hawk HT10
- Hawk DTC-60
- Hawk DTC-70
- PFC 97 Compound
- PFC 01 Compound
- Raybestos ST-42
- Raybestos ST-43

1250F+ Ultra-High Temperature Race Pads including:

- Ferodo DS3000
- Ferodo DS3000+
- Ferodo DS3000 Endurance
- Ferodo DS1-11
- Hawk HT10
- Hawk HT14
- Hawk HT15
- Hawk DTC-60
- Hawk DTC-70
- PFC 01 Compound
- PFC 03 Compound
- Raybestos ST-41
- Raybestos ST-42
- Raybestos ST-43

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

If you like the PFC-Z except for the fact of the initial bite then I think you would like the Hawk HP+. I tried both for AX and was sold on the HP+. As a matter of fact I might still have some HP+ pads from my C4 sitting in the closet. I'll look. They're yours if I have them.

When I went from the Z06 pad to the Carbotech XP8 I started cracking rotors. I attribute that to an entry level race pad vs a street pad. More friction, higher heat range, more energy to disperse. Guys with identical cars as mine were cracking rotors running Hawk Blues. Race pads are not nice to rotors. Some more than others.

Vincent Keene · **Posted:** Thu Feb 01, 2007 9:36 am

Graham Jagger wrote:

If you like the PFC-Z except for the fact of the initial bite then I think you would like the Hawk HP+. I tried both for AX and was sold on the HP+. As a matter of fact I might still have some HP+ pads from my C4 sitting in the closet. I'll look. They're yours if I have them.

Thanks Graham. Can the HP+ serve as my street pads as well? Are they noisey? Dust bad?

If I could use the same pads for street and track that would be great.

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Graham Jagger wrote:

When I went from the Z06 pad to the Carbotech XP8 I started cracking rotors. I attribute that to an entry level race pad vs a street pad. More friction, higher heat range, more energy to disperse.

Not unless you're going faster.

E=1/2 mv^2. Applies to every lap and every brake compound last time I checked.

For race pads to be able to work at higher temps, they deposit different compounds on the rotor than street pads. Who knows what compunds those are... Or what phase changes they go through, or how the steel is being transformed. Street pads are designed to be easy on rotors, low noise, long life. Race pads are designed to work in extreme heat, consumables / cracked rotors / wear rate be damned. It's no surprise to me anyways that race pads tear up rotors, but it's not directly due to higher temps / friction / heat.

Chuck Branscomb · **Posted:** Thu Feb 01, 2007 11:22 am

Speaking of rotor deposits...I've had great success leaving PFC97, PFC01 and HT-10's on for a few days after track events to clean off their deposits from the rotors. At low street braking temps, they act like a lathe on the deposits from the track weekend. Within a few days the rotors are nice and clean -- on go the street pads.

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

MikeWhitney wrote:

Not unless you're going faster.
E=1/2 mv^2. Applies to every lap and every brake compound last time I checked.

You'll need to add a lot more parts to the equation to define this problem mathematically. That is a tad over simplified.

MikeWhitney wrote:

For race pads to be able to work at higher temps, they deposit different compounds on the rotor than street pads. Who knows what compunds those are... Or what phase changes they go through, or how the steel is being transformed. Street pads are designed to be easy on rotors, low noise, long life. Race pads are designed to work in extreme heat, consumables / cracked rotors / wear rate be damned. It's no surprise to me anyways that race pads tear up rotors, but it's not directly due to higher temps / friction / heat.

One thing we agree on for sure. Pads and rotors are consumables.

Understanding the whole metallurgy process is beyond me. I'm looking at more from what I learn from the brake vendors websites and what I see at the track.

Take that same Cavalier and only switch brake pads from a street compound like an HPS to a HP+ to a Blue and the rotor undergoes different amount of friction and heat generation. The .mu of the pads is different. So affected its bite and heat ceiling. Instead of braking at the 5 marker you move down to maybe the 3 marker. You just forced that same car to shed the same amount of speed in the 3/5ths the distance and in 3/5ths the time. That is even more energy(heat) that has to be dissipated somewhere. That somewhere is the pad/rotor/tire.

The "heat checks" show up. Then the rotor cools too fast in the pit area and you hear the lovely "ting" and go look at the nice split in the rotor. Ever notice it mainly happens on the outside face? Why? Because it cools much faster than the inside face. While this may sound silly. One of the guys took MDF boards and cut them into circles with small mounts. After a session he goes right into the pit area and slides them against the 2 front wheels. It blocks the outer face of the rotor from fresh air or breezes that the inside face never sees. It is his attempt to get the inside and outside faces of the rotor to cool together and at a slower rate. He swears it gets him an extra weekend or two out of a front rotor. And he is running hardcore race pads so those rotors are hot!!!

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Graham Jagger wrote:

MikeWhitney wrote:

Not unless you're going faster.
E=1/2 mv^2. Applies to every lap and every brake compound last time I checked.

You'll need to add a lot more parts to the equation to define this problem mathematically. That is a tad over simplified.

Graham, I was replying to your statement that race pads create more friction and run hotter. It has nothing to do with the material in the pad. If you brake from 120 to 60 MPH in 500 feet, no matter what pad you have, the same amount of heat is created.

Speeds being equal, race pads run no hotter than street pads. It's very simple physics and conservation of energy.

Now with race pads you probably *can* brake in shorter distances or deeper, so yes you can get them hotter than street pads and the resulting thermal stresses on the rotors WILL be higher.

I was just trying to clarify the point that the energy and temperature created doesn't change with materials -- just speeds and driver input.

Clear now? Or do you really want more equations.

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Graham Jagger wrote:

Take that same Cavalier and only switch brake pads from a street compound like an HPS to a HP+ to a Blue and the rotor undergoes different amount of friction and heat generation. The .mu of the pads is different. So affected its bite and heat ceiling. Instead of braking at the 5 marker you move down to maybe the 3 marker. You just forced that same car to shed the same amount of speed in the 3/5ths the distance and in 3/5ths the time. That is even more energy(heat) that has to be dissipated somewhere. That somewhere is the pad/rotor/tire.

Sorry Graham I'm going to have to chime in here too -- I know you're probably getting frustrated with me, but I want to make absolutely sure that no one confuses the two issues you are lumping together:

1. The mu/friction curve/etc of a brake pad doesn't matter at all if you're able to bring a tire to lockup in a braking zone. It's simply a function of how hard the driver is pressing on the pedal. A really high Mu pad does not slow the car down faster than a low Mu pad if both pads are capable of lockup. On a a cold street pad (first few laps) or a hot race pads a driver should be able to brake at the same marker.

2. Repeat after me: Race pads do not shorten brake distance due to more deceleration than a street pad -- UNLESS the street pad has heat soaked and is not able to bring the tires to lockup.

Race pads to 2 things: (1) resist heat soak, or reduction in Mu at high temps. This is where street pads fail. (2) improve transient response -- that initial moment of braking and during release, and during modulation.

In Vincent's case for example, where the car is "overbraked". The stopping distances between street and race pads should not be different at all. And if they are different, it is only because of transient response improvements. A pad like an HP+ has excellent transients and would probably be a great choice for an overbraked car.

Bernie Baake · **Posted:** Thu Feb 01, 2007 4:59 pm

MikeWhitney wrote:

Now with race pads you probably *can* brake in shorter distances or deeper, so yes you can get them hotter than street pads and the resulting thermal stresses on the rotors WILL be higher.

Isn't that the point of "race pads"? To brake in shorter distance ? If you were going to brake in the same distance as oem why bother changing anything. Braking distance is the major variable you left out of your equation, as well as a few others I can think of just off the top of my head. Heat transfer coeficients of the pads and the material they deposit on the rotors, for one, and a load more that I don't know of. Assuming the rotors and the wheels and the rest of the metal around the braking system that dissapates the heat of braking is the same. I agree the energy required to stop or slow the vehicle to a speed is the same however the heat rise involves many variables. Number of applications also seems germain in developing total heat rise.

Wes Eargle · **Joined:** Mon Oct 27, 2003 9:47 am **Posts:** 3683

Bernie Baake wrote:

Isn't that the point of "race pads"?

Tires are what stop your car, not brakes. Brake pad choice is all about heat management after your first braking moment. GRM had a great article on brakes last year, lemme see if I can find it ...

edit: It's here.

David Teague · **Posted:** Thu Feb 01, 2007 5:16 pm

Bernie Baake wrote:

MikeWhitney wrote:

Now with race pads you probably *can* brake in shorter distances or deeper, so yes you can get them hotter than street pads and the resulting thermal stresses on the rotors WILL be higher.

Isn't that the point of "race pads"? To brake in shorter distance ? If you were going to brake in the same distance as oem why bother changing anything. Braking distance is the major variable you left out of your equation, as well as a few others I can think of just off the top of my head. Heat transfer coeficients of the pads and the material they deposit on the rotors, for one, and a load more that I don't know of. Assuming the rotors and the wheels and the rest of the metal around the braking system that dissapates the heat of braking is the same. I agree the energy required to stop or slow the vehicle to a speed is the same however the heat rise involves many variables. Number of applications also seems germain in developing total heat rise.

That would be true if your brake pads and rotors stopped the car. Your tires are the major contributor to stopping distance. If your current brakes can lock up your tires, putting different pads are not going to decrease you stopping distance. "race pads" will provide a the ability to modulate your brakes and better initial bite will get the slowing down process started better, but they are not going to shorten stopping distance very much.

edit - Wes beat me to it.

Bernie Baake · **Posted:** Thu Feb 01, 2007 6:08 pm

David Teague wrote:

Bernie Baake wrote:

MikeWhitney wrote:

Now with race pads you probably *can* brake in shorter distances or deeper, so yes you can get them hotter than street pads and the resulting thermal stresses on the rotors WILL be higher.

Isn't that the point of "race pads"? To brake in shorter distance ? If you were going to brake in the same distance as oem why bother changing anything. Braking distance is the major variable you left out of your equation, as well as a few others I can think of just off the top of my head. Heat transfer coeficients of the pads and the material they deposit on the rotors, for one, and a load more that I don't know of. Assuming the rotors and the wheels and the rest of the metal around the braking system that dissapates the heat of braking is the same. I agree the energy required to stop or slow the vehicle to a speed is the same however the heat rise involves many variables. Number of applications also seems germain in developing total heat rise.

That would be true if your brake pads and rotors stopped the car. Your tires are the major contributor to stopping distance. If your current brakes can lock up your tires, putting different pads are not going to decrease you stopping distance. "race pads" will provide a the ability to modulate your brakes and better initial bite will get the slowing down process started better, but they are not going to shorten stopping distance very much.

edit - Wes beat me to it.

That statement is only true till the heat builds up and causes your brakes to fade. then you want race pads to allow you to stop in a shorter distance than your oem pads. The build up of heat is what varies the stopping distance Both in tires and brakes. And Wes I agree, tires stop the car. With brakes on the pavement, without brakes on the tire wall. Try it sometime and see.
Now I'll read the article and see if I have to pull my foot out of my mouth

Bernie Baake · **Posted:** Thu Feb 01, 2007 6:29 pm

Wes and David, and interested others you need to read or reread that article. the addition of race quality pads decreased stopping distance and increase negative G loading. Thats as per the test in that article that Wes linked to.

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