Cryo Treatment Tech

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

MikeWhitney wrote:

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:

Not frustrated with you at all Mike. This is a good discussion :thumbsup:

Quote:

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.

Now you are adding in another variable. Tire lockup. It is another integral part of the picture here. But I disagree that different pads do not affect how fast you can slow down the car. If the tire has not reached lockup.
See below on #3

Quote:

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.

Not even if it was snowing in hades :wink:

See below on #3

Quote:

3. 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.

This is where we disagree. You are not giving brake pads and their functions enough credit. They do more than 2 things. We both agree that different grades of pads (1) resist heat soak, (2) improve transient response. But I will add a couple, one you don't agree on (4).

(3) initial bite (moderate to aggressive)
(4) torque (medium to very high) (this is NOT initial bite)

For example: (from Hawk)
Blue - Medium/High torque
HT10 - Intermediate to high torque with a smooth initial bite
HT14 - Very high torque with aggressive initial bite

The amount of torque IS going to affect how quickly the car can decelerate right until tire lockup occurs. So with a tire capable of better grip, like a race tire, those high torque pads can slow you down faster. The tires slow the car down but the calipers/pads/rotors are the catalyst that makes it happen.

Quote:

4. 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.

[/quote]

I agree with you that since he went with the BBK upgrade he probably doesn't need a full on race pad. The system is not being overworked on his car. The question would be is it still enough to heat soak the pads and have them fade based on how he drives the car or not? And is it true based on the track/course he is on? And how much does ambient temps affect this. Feb @ 40deg or July @ 90+deg. A few more variables to test.

David Teague · **Posted:** Thu Feb 01, 2007 10:06 pm

Bernie Baake wrote:

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

I would agree you do put race pads on a car to get the same braking from the 1st stop of the session to the last stop of the session., but that is not what you implied in your previous statement, which was simply you put race pads to get shorter stopping distance. I have ran "street Pads" at several track events and I can tell you that at the beginning of the session I am braking at the same point weather I am on street pads or race pads. I may need to use more pressure on the pedal with street pads, which is what Graham is alluding too. With the same about of pedal pressure the race pads generally will stop you quicker if you not locking up the brakes ( or engaging ABS) However if you simply stand on the brakes for the race or street pads to where the tires lock up your stopping distances will be very similar.

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

Vincent Keene wrote:

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.

Vincent, I found the pads. Sorry they aren't Hawk HP+. I must have left them on the car when I sold it or gave them to the guy with the car. But I do have a set of PFC pads, not the -Z. They would be fine for the street or get home pads. There is .250-.275 on the rears and .275-.300 on the fronts (material, not including backing plate). Plenty of meat. They are yours if you want them.

As far as the HP+ goes. If they don't heat soak and fade on you on the track then that would be great. Good initial bite like you are looking for. And much less pedal pressure required compared to PFC-Z. They make good AX pads too. You can most certainly drive them on the street. There are only 2 issues with them on the street. They will squeak if you just putt around all the time. Do some good hard stops and they stop squeaking for a while. The big issue is they dust a fair bit and the dust is nasty. You need to wash the wheels fairly regularly or the dust will stick permanently. They are what I would consider a crossover pad. Part high performance street and part track.

Might be just the right pad for you since you have the big brakes. The price on them is good and you might find some used ones on CF in the C4 parts for sale section so you can try them.

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

OK Graham and Bernie maybe we're not getting through to you. Graham, most of your other points are all about transient pad response -- and all of which I agree with.

So just do this thought experiment for me.

I have a car. It has ABS. I am going to do 2 cold braking runs from say 80 MPH to 0
MPH.

First time is with Hawk Blues

Second time is with organic Pep Boys pads

I accelerate to 80 MPH and mash the brake pedal as hard as I can into full ABS on both runs. ABS continues until 0 MPH.

Question: Is there any difference in the amount of time the car takes to slow from 60 MPH to 20 MPH?

Bernie Baake · **Posted:** Fri Feb 02, 2007 8:54 am

Mike, in your test the braking distances would be the OE pad would stop in a shorter distance, From experience the Carbotech pads I use need to be heated up. However once they are warm they pull the car down incredibly fast, as compared to the OE pads. Or at least I feel they do.
But wait there's more here's Per Schroder's test on a honda civic, tested in Jan 2005 GRM. In short if you dont want to read it, the Oe pads stopped in about 160 ft. the carbotech's in 140 feet pulling higher -G's, when both were hot.

Here's the article

Before performing any baseline tests, we refilled the brake system with Castrol LMA brake fluid, bled the brakes and checked our tire pressures. Except for the Personal steering wheel and AutoThority
short-shift kit, the rest of the car was bone stock.

We grabbed our Vericom VC2000PC on-board data acquisition system, put J.G. (our resident hot-shoe driver) in the driver’s seat, and set out for our top-secret test site.

Then we did some baseline tests. Our first stop from 60 mph took only 148 feet while generating .875g of force. The stop took 3.62 seconds, and some right-rear lockup was observed.

By our second stop, the pads were already showing they were giving up the fight-it took an additional 10 feet to stop from 60 mph. Our g force readings had fallen to .840g, and the stop took 3.83 seconds.

Things didn’t get any better after that. Our CRX took 161 feet to come to a halt by the fourth run. Fade
was running rampant, and it was already time to allow the brakes to cool off. We ran some more stops that day, and our g force readings hovered in the .84 to .88 range. The average was .858g over the eight stops we measured. Before heading home, we had to drive around a bit so the brakes could cool.

Looking to ImproveWith our baseline figures in hand, we started our search for new pads and shoes. This is a street car, remember, so cold stopping power is very important. We also plan on autocrossing the car, so fade and modulation were also high on our list.

Larry Narcus at Carbotech listened to our requirements and matched us up with the goods. Up front we would try his new "Mean Green" Kelated-metallic pads. These are designed to work in the 100- to 750-degree environment, perfect for the street and autocross use. He also promised no
fade and excellent modulation. For the rears, we would try his Silver Streak shoes. These offer a slightly lower friction coefficient than the Mean Greens and would compliment the Kelated-metallic
front pads, he said.

Randy Duval at AllSpeed helped install the new pads and shoes, which were no harder to install than your garden variety OE pieces. We found our original-equipment pieces to be rather worn, probably not entirely unlike most street cars out there. Our rotors were looking a bit thin, but we decided to keep them on and see what the pads alone would do.

With the Carbotech pieces installed, we followed Larry’s instructions and properly bedded in the pads.
Then it was time for more testing.

J.G.’s first run on the Carbotechs registered an astonishing .929 g. However, the stop took 162 feet. This was probably due to the fact that the pads were still unfamiliar with the irregular surface of the rotors. Also, our CRX had average street tires on it, but like we said, we wanted to simulate a
real-world test.

The next stop saw the distance plummet to 144 feet at .896g. The stop took 3.40 seconds and J.G. reported that modulation was excellent.

We ran seven more stops that session; by the end we had the stopping distances down to 141 feet. Even towards the end of the test, the brakes were still stopping well, showing g force readings as high as .995g after half a dozen repeated stops from 60 mph. We averaged .923g over the nine stops we recorded with the Carbotech shoes and pads. Our stops took as little as 3.18 seconds and the stopping distances were now as short as 140 feet.

At no time during this test did we observe fade or any modulation problems. Unlike the stock pieces, we never had to allow the brakes to cool off once we installed the new shoes and pads.

These tests were all conducted literally minutes after the Carbotech shoes and pads were installed, so
naturally the braking performance should only get better as the pads conform to the rotor surfaces. We have gone ahead and ordered some new rotors; we can’t wait to see how the pads work against
a fresh surface (we’ll have the pads resurfaced before installing them). As for tires, we’ll test the car again once some fresh rubber arrives. Remember an important fact: the brakes stop the wheel; the tires stop the car. Your brakes are only as good as your weakest link in the system, and right now our tires can’t keep up with our brakes. And yes, all of this data will appear in a future issue.

This simple brake pad and shoe change has given us fantastic brakes for a fraction of the cost of a
over-sized, drilled rotor conversion. It may not look sexy, but it certainly gets the job done.

Any down side to these pads? Not really, although we have gotten some squeal under low line pressure situations (like when slowly rolling to a stop). There is also some dust, but that’s why wheel cleaners were invented. Still, for day-to-day driving, we have to say that these brakes are perfect.

Frank Catena · **Joined:** Wed Aug 27, 2003 1:08 pm **Posts:** 418

Can I raise my hand?

Stopping distances should be the same. I surmise even without ABS and with just plain locked rotors.

I'd even offer that the heat load is the same.

The only advantage I see for a high mu pad in a single stop is you might lock those rotors (or engage the ABS) a tad quicker because the higher torque pad locks the rotors for less pedal pressure. This is what I think Mike is calling transitory behavior. Mike accounts for this by asking about the 60-20 portion of an 80-0 stop.

No doubt that in repeated stops the race pad should be more consistent as the organic fades. Unless, of course, your fluid boils first :-)

If the pad doesn't have the ability to lock the brakes (either because they're too cold or the fluid boils) all bets are off.

Frank

Chuck Branscomb · **Posted:** Fri Feb 02, 2007 9:19 am

Frank Catena wrote:

Can I raise my hand?

Stopping distances should be the same. I surmise even without ABS and with just plain locked rotors.

I'd even offer that the heat load is the same.

The only advantage I see for a high mu pad in a single stop is you might lock those rotors (or engage the ABS) a tad quicker because the higher torque pad locks the rotors for less pedal pressure. This is what I think Mike is calling transitory behavior. Mike accounts for this by asking about the 60-20 portion of an 80-0 stop.

No doubt that in repeated stops the race pad should be more consistent as the organic fades. Unless, of course, your fluid boils first :-)

If the pad doesn't have the ability to lock the brakes (either because they're too cold or the fluid boils) all bets are off.

Frank

Ding! You perfectly summed up the situation, so I don't have to concoct a post. Head of the class for you sir.

Chuck

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

Bernie Baake wrote:

Mike, in your test the braking distances would be the OE pad would stop in a shorter distance, From experience the Carbotech pads I use need to be heated up. However once they are warm they pull the car down incredibly fast, as compared to the OE pads. Or at least I feel they do.

I didn't ask which pad would stop the car quicker.

I asked which pad would slow the car the quickest from 60-20 mph from 80 mph, while in the ABS.

Answer: Same, like Frank and Chuck say.

PS - I did read the article, and I do understand everything they are talking about. They tend to mix the 2 concepts of transient response and threshold braking too. But hey, it's written by an autocrosser, what do they know about brakes?

It's funny, they're talking about the "Kelated Metallic" pads in there -- once when I was on a search for the absolutely fastest-warming, highest possible initial bite (I said "I want to just LOOK at the brake pedal and feel the car start to slow down), Larry recommended the KM pads -- "They'll knock your dick in the drt". He said!

Vincent Keene · **Posted:** Fri Feb 02, 2007 10:13 am

Graham Jagger wrote:

As far as the HP+ goes. If they don't heat soak and fade on you on the track then that would be great. Good initial bite like you are looking for. And much less pedal pressure required compared to PFC-Z. They make good AX pads too. You can most certainly drive them on the street. There are only 2 issues with them on the street. They will squeak if you just putt around all the time. Do some good hard stops and they stop squeaking for a while. The big issue is they dust a fair bit and the dust is nasty. You need to wash the wheels fairly regularly or the dust will stick permanently. They are what I would consider a crossover pad. Part high performance street and part track.

Might be just the right pad for you since you have the big brakes. The price on them is good and you might find some used ones on CF in the C4 parts for sale section so you can try them.

Hmm...so what about the Hawk HPS? Mike do you have any experience with them?

Edit: BTW, I do at least understand that once the braking system can acheive lock-up (engage the ABS in my case) that's all it can do. IOW, I can out brake my tires (Azenis 615s) all day long with no problem!

Jason Mauldin · **Posted:** Fri Feb 02, 2007 11:03 am

Bernie Baake wrote:

Mike, in your test the braking distances would be the OE pad would stop in a shorter distance, From experience the Carbotech pads I use need to be heated up. However once they are warm they pull the car down incredibly fast, as compared to the OE pads. Or at least I feel they do.

I think that is the key.

They work better, because you have more confidence in them to work. I wonder how much of that plays a part in all of these braking test?

Bernie Baake · **Posted:** Sat Feb 03, 2007 10:37 am

OK everyone, I conceed your all brake wizzards. Explain for the dummy when GRM tests this theory. It does not hold up. tests show that the Their Kelated Metallic Pads stopped the civic in 87.5% the distance that the organic ones did

Matthew Fortner · **Joined:** Sun Mar 21, 2004 12:21 am **Posts:** 384

Racing pads in the past have either offered equal or below par stopping to street pads until up to optimal temp. I think we are seeing that change as pad compound technology advances.

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

MikeWhitney wrote:

OK Graham and Bernie maybe we're not getting through to you. Graham, most of your other points are all about transient pad response -- and all of which I agree with.
.
.
.
Question: Is there any difference in the amount of time the car takes to slow from 60 MPH to 20 MPH?

I'll agree that the 1 stop test with cold pads will come out even give or take a few feet. But after that your organic pads are useless. So that experiment is good for 1 stop 1 time. Most of my observations are about initial response and transient response over the course of a session. Since I never go to the track to do 1 stop and then go home :wink:

Back to Vincent cracking rotors... and why... ?

Chuck asked if he had pictures. I looked closely at the rotor he cracked at the PCA event when he had the Carbotech XP8 on the front. Those rotors looked identical to mine and several other folks rotors I have seen. Plenty of tiny heat checks (1/4"-1/2" little cracks) all over the rotors. The crack came from one of those that finally split. I attribute that to thermal cycling. I think I still have 1 left in the garage that I can take a picture of. If the pads weren't getting into their range then I would expect a nice polished surface. As you noted using race pads for a week on the street polishes the rotors up. Almost like a lathe because the pads don't get hot enough and just scuff the rotor surface. Vincents rotors were not shiny or grooved up. You could also see heat burnish marks.

So I'm not convinced that he is not getting enough heat in the pads to make them work. Even with the upgraded brakes. Since he is working them for 20-25 minutes at a time. Who knows how quickly he is getting them up to temp though. Only way to know is put temp tape/paint in place and then run a 5-min session, 10-min session, etc... Since Vincent said he never suffers brake fade we can assume that he isn't hitting 1,000 deg with the XP8 or over 750 deg with the PFC-Z. Since that is the usable heat range of those pads. If I could run a lower grade pad and still not get fade I'd jump on it since it is easier on the rotors and the wallet.

Mike commented that when he used Carbotech the pads looked like potato chips and the backing plates were bent/warped. This may have more to do with his cars braking system and the Carbotechs. I have 2 sets of Carbotechs (XP8 all around, and XP10/XP8 pairs). The XP8 set are almost worn out. The pads do not look like potato chips and the backing plates aren't warped. The XP10/XP8 only have 2 events on them and look the same, only with more pad material. They do taper on my car, and that is due to the caliper design.

Since Vincent is using C4 calipers, which are similar to the C5 calipers. I would expect him to see pad taper if they were being worked really hard. So that BBK upgrade can handle his cars weight/speed easily.

I think dropping down a grade in pad will be the best option for getting the rotors to last longer. The HP+, or Panther, or maybe try this new sponsors pads and run the Ferodo DS2500. Jim is having good results with his Camaro. They are listed as streetable pads so they could be run all the time.

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

Vincent Keene wrote:

Current Brakes (from a C4 Corvette)

Front 12.2” x 1.1 thk rotor, dual piston PBR floating caliper, Carbotech XP-8 pads
Rear 12” x .79 thk rotor, single piston PBR floating caliper, NAPA El-cheapo pads

For 2006, I ran Carbotech XP-8s up front, and the PFCM-Z pads in the rear. I ran 7 events with this setup and no ducting. The brakes worked flawlessly…until I cracked a rotor at the PCA event.

You told me that you were going to use the calipers off a ZR1. The ZR1 uses the J55 brakes (HD) from the Z51 option package. Larger caliper than standard and larger rotor. The rotor in the J55 option is 13", not 12". So you have the J55 HD caliper with the JL9 STD rotor. That is a mismatch. They went to the 13" rotor with the J55 caliper to help with heat dissipation. The STD caliper is only a bit smaller, physically, and uses smaller pistons. Mounting brackets are different but both options use the same brake pads.

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

Graham Jagger wrote:

Mike commented that when he used Carbotech the pads looked like potato chips and the backing plates were bent/warped. This may have more to do with his cars braking system and the Carbotechs.

Bent the backing plates on both XP8s and XP10s on both a BMW E30 and ITA prepped Honda Civic. Also have bent Hawk Blues on the E30 before finding better pads. I get brakes *really* hot -- I was just going over the temp range of those pads and instead of backing off, just pushing the pedal harder.

Never had problems with PF90s on the E30, PF97s on the Civic, and Hawk HT-10s on the E30 or the M3. Those are my pads of choice for track duty these days.

PF90s were my favorites overall -- most rotor friendly and longest lasting. The don't make them any more. I'd call PFC97's and HT-10s a tie, liked them both but they were on different cars.

Just my experiences...

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