fleming23

I'm not really sure that I am asking for help just yet but some rotor paint confirmed my suspicions that I am definitely cooking my front brakes.

This was a single session with CHIN at Road Atlanta running maybe at 7/10ths while I was trying to feel the car out. So only 25-30 minutes not a full day or weekend for that matter.

Front rotors







Rears for reference


After the first session, the car was sitting in the paddock with the hood up when the hydroboost reservoir exploded and rocketed off the car in a very violent fashion (see photo below.) Not sure the two are in any way related but I was not pushing on the car very hard at all....








I really need cooling ducts but no one makes a duct for my ridetech equipped, baer brake 71 Corvette.... I attempted to fab up one on my own and was told it would likely cause more problems than no duct at all. To clarify, the apparent issue with my attempt to cool the rotor was the location of the duct opening in that it would not direct the air into the hat of the rotor and out the vanes. Some of the cool air would likely hit the rotor face which I was told could cause some major cracking.

This is the duct work I was going to use but disconnected prior to going on track

FASTFATBOY

I don't think you need ducts but judging by the pad being wiped onto the rotor you need a brake pad with more heat range.

What pads are on the car?

How is the hydroboost connected to the brakes? I know how they work, what else does the fluid run?

EDIT

Ridetech has a yellow car like yours they track. What is on that car?

fleming23

I am running PFC-01s both front and rear. I previously used Carbotech XP12/10s and was experiencing major fade but think it was due to me boiling the Castrol SRF fluid possibly more than the pad having issue (which would make sense if I am indeed getting as hot as the temp paint indicates.) Regardless, I heard great things about the Performance Friction 01 compound and thought I would give it a try.

Hydroboost is no longer connected but is basically just a hydraulic booster. The power steering pump provides the assist to the master cylinder, that is all.

My car is effectively a duplicate of the RideTech 48-Hour car except they are using 13" brakes vs my 14" rotors but basically the same brake package with a few exceptions like the master cylinder used, my previous hydroboost etc. I believe they were using Hawk DTC 30s but do not know if that has changed.

FASTFATBOY

Does the Ridetech car have manual brakes or a cooler on the power steering.

I don't see you boiling the fluid running 7/10's unless there is moisture in the system or a brake line is close to the exhaust. Did the pedal go to the floor or?

If those are PFC-01's I would do a better bedding procedure.

If the car was mine I would put manual brakes on it and a cooler on the power steering.

chetly

I'd also look into putting your cooling scoops somewhere on the front of the car and try to attach the duct to the front of the spindle so the air does in fact go into the hub instead of the back face of the rotor.

fleming23

Ridetech car is running manual brakes, which is what I am in the process of converting to now. I am not aware of a PS cooler, but did not pay too much attention to that aspect. It is on my "to-do" list but now that the hydroboost has been removed, I am hoping my Turn-One pump will not be nearly as labored at the track.

What exactly are you referring to by a better bedding procedure? Scuff the rotors with scotchbright and try to bed again? How is that relevant to the heat issue?

That is easier said than done on a 71 Corvette. This isn't a c5 or c6 with factory ducts and room to run them. It is relatively limited on how to get ducts to the front without adding some ****** looking chin spoiler. Even the spindle duct....If I had something I could get to work, I would be all for it. As it stands, the cooling ducts are on the front(ish) side of the spindle but I cannot get them any closer. There were made for a Porsche 911 if I remember correctly and I cut and molded them to work on my car. As it stands, there are no cooling ducts "kits" available for me. I wish there were!

rfn026

That duct is from a 911 kit. It works fine in most circumstances.

You might want to talk to a brake company about your braking technique. Don't bother with the Chin instructors. Go right to the source. Ask them what they suggest.

There's not much the manufacturers haven't seen before.

Richard Newton

FASTFATBOY

Judging from the pad swipe marks on the rotors the pads were not bedded properly. I doubt you are overheating a PFC-01.

Do you have brake shudder?

I would sand the rotors with 80 grit sand paper, clean with brake clean and re-bed. When I bed in brakes it literally smells like a truck coming down a BIG mountain. When I think they are too hot, I do it a couple of more times.

I don't think you have a heat issue.

Put some temp strips on the caliper, Alcon makes some nice ones.

You said you had "brake fade". Did the pedal go to the floor?

Be careful about over cooling a rotor, I learned this the hard way. Heat cycling a rotor DRASTICALLY shortens the life of a rotor. You want heat in the rotor and maintain that heat.

fleming23

I definitely brake late and hard. I don't typically have instructors with me as I am beyond those groups but even so, wouldn't rely on someone who doesn't know this car to give me much mechanical advise. Even when I was still getting through the Chin ranks, I never had an instructor say anything to me about my braking.

I am talking with Baer but it is a slow process. SEMA last week (and the weeks leading up to it) did not help.

Not following you on the not having a heat issue.... The paint temp is pegged hot, how would that not be a heat issue? Also, I have used the Alcon temp strips and they too looked like they were maxed out which is why I went to the rotor paint as it changes color rather than just small blocks that go from white to silver (or whatever the Alcon strip did, I don't remember.)

With the brake fade, the pedal got longer and lost bite. I would go into T1 at Road Atlanta and the pedal would be nearly at the floor with very little bite. It seems by the time I would get to the big back stretch it would recover a bit but the only way to get the pedal to return completely would be to bleed the fluid.

fleming23

Also, a note on the bedding of the PFC-01s

I did this on the street to some extent but really the "warm-up" session which was open to all cars first thing in the morning should have been enough to get the pads bedded per PFC's instructions

"If the discs were previously being used with Performance Friction pads, then the bedding procedure will be achieved quickly with new PFC pads. If the discs were previously bedded using a different manufacturer's pads then the process will take slightly longer. Again, with brake cooling ducts open and fully functional, perform the following procedures.

On the first lap, perform several snubs with progressively higher pedal pressure and braking force and from higher speeds. You will feel the effectiveness of the brakes increase with each successive brake application. This should take 6 to 10 snubs per lap and is usually completed in one or two laps. If non-PFC friction materials were previously run on the discs then this procedure could take as many as three to five laps. This is because the non-PFC friction material transfer layer must first be cleaned from the disc and then a fresh layer must be imparted to the disc.
Running additional laps is the best way to accomplish the new transfer layer and, due to the higher surface temperatures, will assure a complete removal of the old friction materials from the disc. Braking effectiveness should be excellent at this point and the car can be driven normally."

FASTFATBOY

So, you have a pro race pad(PFC-01) and you think you are fading them running 7/10's? How much power is in that car?

Temp strips have actual temp steps on them.

Check your wheel bearings as that appears to be a radial mount caliper. If you have a loose one it will give the same symptom as a low pedal.

Also check for dragging brakes.

Also check to see if the rears are doing their fair share of the work.

Not saying you don't have the problems you say, but I can tell you this...I was a brake destroyer in my 3800lb 385 rwhp 99 Z28. I was like the worst EVER in killing brakes in that car. I learned a ton from running that car.

Just trying to give objective opinions.

fleming23

It isn't a race car, nor is it the fastest thing on track. It does make a mid 400 hp to the tire and I am constantly braking from 135-140 down to 50 or so in turn 10a at Road Atlanta. Also, I never said I was fading the brakes running 7/10ths. The rotor temp paint is from running around at 7/10ths. When I can actually get out there and run hard, that is when, in the past (also using SRF and Carbotechs), I have experienced fade. I am now using Torque RT700 fluid and PFC-01s but have just the single session on the current brake set-up. Am I overheating the pad, I have no idea, all I am basing my information on is the temp paint. I find it difficult to believe I am cooking either XP12s or PFC-01s but I do believe the fluid is getting cooked based on how I can lose pedal and it not return completely. In the last session and the one I referenced at the beginning of this thread, I did not go out and run as hard as I could because I changed enough things that I wanted to get comfortable and gain trust in the car first. Even so, after a number of laps the pedal was not super solid or reassuring but this could be in someway related to the hydroboost failure, not sure.

Yes, the temp strips have little boxes that progressively change from one color to another as the calipers get hot. I tried to find a picture of them but guess I deleted it...all the boxes were silver or grey (IIRC) at the end of a session running the XP12s at Carolina Motorsports Park.

Wheel bearings have no play at 3, 6, 9 or 12 o'clock. The wheels spin freely in the air. If you press the pedal the pistons seem to return correctly and do not seem to drag or anything like that. I did have an issue with a Baer master cylinder that was not releasing pressure but that was pretty easy to recognize as you could feel it pull the car down while driving.

Regarding the rears - normally the car has almost too much rear bias. At some point I need to plumb in my proportioning valve because there have been times coming into a turn a bit hot that the rear will dance around as it tries to brake too hard. It almost feels about 50/50 in braking which is probably a good thing. When I was getting my sign-off at Road Atlanta a few track days ago, the instructor noted how much the car slid around under hard braking but said he never felt that I was not in complete control of the car and gave me high marks.

Also, I appreciate the comments. I think this is more frustrating as I am left scratching my head as to what to do next. I don't have a plethora of examples to look at from guys running these cars with my set up.

FASTFATBOY

fleming23

I'll put those on next time I go out again (Thanksgiving weekend assuming I can get everything fixed before then) for a second data point. I believe I still have quite a few in my little packet.

johnny c

fleming, I'm the one who sold you the PFC pads. Glad to hear the fade is gone, bummed to see the super high rotor temps. you have a lot of drag in the system if your getting above 1400* in a solid pattern like that. you might be closer to 1600*.

what you have is Drag and a ton of it. that is what is causing the rotors to become super heated.
Drag can be found in a few places,
- Caliper design. if the caliper flexes further than the pistons seals can retract you will effectively be driving with the brakes still on. This will super heat components and cause rotor temps to skyrocket. you have bear brakes, although they are not my favorite brand i haven't heard of them being flexy. Actually they are massive, overweight and they should be super strong. i doubt they would be flexing, but anything is possible.

-Rotors,
When rotors get hot they like to move. they will bend to the hottest side. they can move up to 2mm side to side. again you have the bear rotors and that's not my favorite because they face the rotor. cutting the outer edge of the rotor (and not making it a U shape) removes the thermal stability and can cause the rotor to explode under high heat and deceleration. when i was at PFC we had brembo rotors kicked out of nascar for doing that. that being said it shouldn't cause drag. and you have a 2 piece rotor. the two piece rotors help dissipate heat faster so i don't think the drag is in your rotor.

-residual line pressure
this is what i think is wrong. with that Hydro booster exploding i think it was messed up. it could of kept a residual pressure in the lines. that would cause a ton of drag. If it was my car i would ditch that hydro booster and try to run a vacuum booster. i wouldn't go manual unless you had a dual MC set up. the pistons in the calipers are sized for a boosted set up and switching over to a manual will be a huge PITA. with a manual MC you might be able to see 200Lbs of force needed to slow the car. that's like squatting 400lbs. a boosted set up would be in the 75lbs range.

FASTFATBOY

Also check the length of the master cylinder rod, if it's too long it will cause the dragging.

To check for dragging, drive the car on a small grade put it in neutral and let off the brake. The car should roll freely with no drag. You may have to check the brakes hot to duplicate it.

johnny c

on a side note - i got to try that Torq fluid, if your rotors got to 1400*+ and it never had fade. it might solve the clutch issue i've been having.

fleming23

Thanks Johnny and I remember you both from the Jzilla day at CMP and chatted with you briefly at LS Fest.

I tend to agree with you on everything including the residual pressure caused by the hydroboost. There had to be something going on to cause it to fail like it did.... Ultimately, I am already headed down the path to manual brakes. I have a new 15/16th bore master cylinder installed but the push rod was too short. A new adjustable push-rod should be sitting on my doorstep when I get home so my fingers are crossed I can finally bleed the brakes and move on to other items on my to-do list before I hit the track again.

FAST - With the new adjustable push rod so I should be able to dial the length in perfectly with the new master. But I am well aware of the push rod issues. I went through that with the $400 Baer Remaster that was recently released and did not fit my application.

Smittys67

We are running the 14 inch 6R setup on the 48hr Vette with Hawk CF30 pads just for the record. I'm having no issues with the car. We switched to the bigger stuff shortly after the build. I have ran 20ish events on the same rotors and pads and still have 50% pad left.

fleming23

Thanks for the update Chris! I have been talking to Rick at Baer about this for a while now, trying to figure out what my car is doing. Just got the manual master mounted and my fingers are crossed my issues were somehow tied to the hydroboost or hydro/master combination.