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The back story:
This was my third track weekend with my 2002 Z06. I run Carbotech XP10 up front and XP8 rear.
I had 1 day on the rears at Roebling, and 2 days at Homestead.
At Homestead, my instructor insisted on leaving the nannies on. Both days I ran into a pedal that would get progressively longer throughout the day. Now, we know why
The piston "lands" for the dust seal collapsed.
Has anyone else run into this?
On a better note, I broke 1.50 and the video is here:
Nannies kill rear brakes, "everybody" knows that.
Get new instructor next time who is aware of how Corvettes work. Don't sweat the boots, new ones burn up & melt after 1 session. Leave off.
Originally Posted by jcp907
The back story:
This was my third track weekend with my 2002 Z06. I run Carbotech XP10 up front and XP8 rear.
I had 1 day on the rears at Roebling, and 2 days at Homestead.
At Homestead, my instructor insisted on leaving the nannies on. Both days I ran into a pedal that would get progressively longer throughout the day. Now, we know why
The pads were over 90% (new) going into the event and the inners were nearly metal to metal by the end of the weekend.
The disappointing part of this is that the instructor that I had owns a C5Z, although I don't believe he has abs or active handling on the car any longer.
I'll replace the pistons (possibly with steel) and keep the nannies off.
Wow! never seen that. In the earliest days of T1 racing we were restricted to stock brakes. Minimum pad was xp10's in rear and 12 or 16's in the front. I can't quite remember. We also killed a rotor on day 3 and expanded out caliper bodies within the season causing us to replace calipers annually. It looks like you are using up your brakes pretty good which might mean you are getting pretty fast. You may want to go to AP's or Stoptechs. With my Stoptech T1 brakes I can race more than a season on 1 set of pads and I have never worn out rotors but I still change front rotors every few years. I have never changed a rear rotor. Ask around you can use a stock C6 brake caliper which is a little thicker with some modifications that all the use of a thicker pad plus some Ti shims. The shims seem to spread off some heat. Check with SCCA/NASA racer Jim Tway on this site. He can hook you up with a more reliable set-up.
I would not be so quick to throw the instructor under the bus unless you did not need the instruction in the first place.
The boot is shot but it is not melted so it does not look entirely like a heat issue. T deform that piston as a result of heat I would think that the caliper would be burnt and there would no NO rubber left anyplace.
Active handling will kick in and work the rears but not to the point of destroying the inner pad alone.
The piston does not appear to have made full contact either.
More to it than meets the eye and IMHO you are grossly unfair in blaming your instructor.
Wow! never seen that. In the earliest days of T1 racing we were restricted to stock brakes. Minimum pad was xp10's in rear and 12 or 16's in the front. I can't quite remember. We also killed a rotor on day 3 and expanded out caliper bodies within the season causing us to replace calipers annually. It looks like you are using up your brakes pretty good which might mean you are getting pretty fast. You may want to go to AP's or Stoptechs. With my Stoptech T1 brakes I can race more than a season on 1 set of pads and I have never worn out rotors but I still change front rotors every few years. I have never changed a rear rotor. Ask around you can use a stock C6 brake caliper which is a little thicker with some modifications that all the use of a thicker pad plus some Ti shims. The shims seem to spread off some heat. Check with SCCA/NASA racer Jim Tway on this site. He can hook you up with a more reliable set-up.
Carl, as a reference point, the Stoptech setup you are calling the TI setup, does it use the ST40 or ST60 and what size front rotor. Thanks.
Ran into the same issue a few years ago. Extreme heat softens the piston metal and causes it to deform under pressure. Here are a couple pics-- you can see how the piston mushroomed around the pad.
My conclusion was that I let the pad get too low. Went into the final session with about 20-25% remaining. (More than a backing plate width so I thought it was plenty.) But the extra friction & heat from AH/TC constantly dragging the brakes burned through the pad [I]much[I] faster than anticipated. Brake material is an insulator; once the pad has worn to the point that it's metal-on-metal, the aluminum piston soaks too much heat and softens.
FWIW, if I were the instructor I would have said the same thing. Still would even knowing what I know now. It's saved my butt in student's cars too many times to ignore. More often than not the student doesn't know that it saved them... If they're at the point that they can safely drive without it, they don't need me as an entry-level instructor.
I have run C6 pads down to almost nothing in the rear but never experienced that. I would generally use 2 fronts to a set of rears and I flip the pads. It looks like it may have been almost metal to metal for awhile and I would think it would have been noticeable ... at least worthy of a check in the pits ??
Yes good pic. The rear pads on the C5 and C6 calipers are deceiving, they wear slowly and have so little pad when new it's hard to really check pad wear without removing them. I suspect there are more of these deformed rear caliper pistons than people realize. Of course these examples are pretty obvious.
I have never tracked my car with the nannies on and my rears last 3 times longer than the fronts. ST 47 front, 45 rear.
Ran into the same issue a few years ago. Extreme heat softens the piston metal and causes it to deform under pressure. Here are a couple pics-- you can see how the piston mushroomed around the pad.
My conclusion was that I let the pad get too low. Went into the final session with about 20-25% remaining. (More than a backing plate width so I thought it was plenty.) But the extra friction & heat from AH/TC constantly dragging the brakes burned through the pad [I]much[I] faster than anticipated. Brake material is an insulator; once the pad has worn to the point that it's metal-on-metal, the aluminum piston soaks too much heat and softens.
FWIW, if I were the instructor I would have said the same thing. Still would even knowing what I know now. It's saved my butt in student's cars too many times to ignore. More often than not the student doesn't know that it saved them... If they're at the point that they can safely drive without it, they don't need me as an entry-level instructor.
The C5 AH system uses the rear brakes to correct understeer and the front brakes to correct oversteer. If you are driving with the system on and it wears the brakes like that it could be an indication of a handling issue that may need to be addressed. The rear brakes will not wear anywhere near that bad if the car is turning in properly in relationship to how much you turn the steering wheel.
Carl, as a reference point, the Stoptech setup you are calling the TI setup, does it use the ST40 or ST60 and what size front rotor. Thanks.
The stoptech SCCA T1 kit was developed and tested on my racecar by stoptech. It is rules limited. It uses st40 front and st41 rear 4 pot calipers and 14 front 13 rear full floating trophy rotors.
The reason for multiple pistons is to control pad taper most problematic as the pad ages. There is some pad taper with the 4 pot and I can only guess less taper with the 6pot. But 6 will not make you stop better. The wear is so minimal that it is a non-issue. Like said I'm getting 1 season on pads! Stoptech has an amazing facility and has entered the oem world like brembo. ST is controling every aspect of the brakes systems even in house manufacture of their own SS braid brake lines for quality control.
In the old days of T1 we spent in between sessions always doing some brake maintenance. Now I can take a nap. With Stoptechs I bleed brakes before the race weekend and don't touch the brakes until the next time I go racing. Also, using cheap valvoline synthetic brake fluid from autozone! No need for expensive Castrol SRF.
The stoptech SCCA T1 kit was developed and tested on my racecar by stoptech. It is rules limited. It uses st40 front and st41 rear 4 pot calipers and 14 front 13 rear full floating trophy rotors.
The reason for multiple pistons is to control pad taper most problematic as the pad ages. There is some pad taper with the 4 pot and I can only guess less taper with the 6pot. But 6 will not make you stop better. The wear is so minimal that it is a non-issue. Like said I'm getting 1 season on pads! Stoptech has an amazing facility and has entered the oem world like brembo. ST is controling every aspect of the brakes systems even in house manufacture of their own SS braid brake lines for quality control.
In the old days of T1 we spent in between sessions always doing some brake maintenance. Now I can take a nap. With Stoptechs I bleed brakes before the race weekend and don't touch the brakes until the next time I go racing. Also, using cheap valvoline synthetic brake fluid from autozone! No need for expensive Castrol SRF.
That is the exact info I was looking for. While I'm not doing W2W, I run hard enough to be tired of the cracked rotor dance in between sessions and the 10mm new brake pads that last me 1 .5 weekends. Not to mention the soft pedal and crazy pad taper from bendy calipers.
Sounds like a good kit and lots of track guys will be interested.
The C5 AH system uses the rear brakes to correct understeer and the front brakes to correct oversteer. If you are driving with the system on and it wears the brakes like that it could be an indication of a handling issue that may need to be addressed. The rear brakes will not wear anywhere near that bad if the car is turning in properly in relationship to how much you turn the steering wheel.
Bill
Can you (anyone) please take a look at the video and let me know if there is something that I am missing?
Ran into the same issue a few years ago. Extreme heat softens the piston metal and causes it to deform under pressure. Here are a couple pics-- you can see how the piston mushroomed around the pad.
My conclusion was that I let the pad get too low. Went into the final session with about 20-25% remaining. (More than a backing plate width so I thought it was plenty.) But the extra friction & heat from AH/TC constantly dragging the brakes burned through the pad [I]much[I] faster than anticipated. Brake material is an insulator; once the pad has worn to the point that it's metal-on-metal, the aluminum piston soaks too much heat and softens.
FWIW, if I were the instructor I would have said the same thing. Still would even knowing what I know now. It's saved my butt in student's cars too many times to ignore. More often than not the student doesn't know that it saved them... If they're at the point that they can safely drive without it, they don't need me as an entry-level instructor.
I am glad to know this has been experienced before, thank you for posting your experience. I didn't expect the rears to get that thin in just 2.5 days, they were nearly metal on metal at the end of the weekend, but, even on day 1, the pedal was getting long. I agree, it's clearly heat from having the nannies on. I can't imagine the rears building that much heat otherwise.
With regards to the dust boots, those were melted at an autocross, by the prior vehicle owner. There didn't appear to be new damage this time out, to the dust boots, just the pistons, pads, and presumably, the fluid.
With regards to the instructor, I wouldn't say I am throwing him under the bus. This was the first instructor that had me run with the nannies on (of 3). At the end of the weekend, he wrote down that in his opinion I should be solo, and I appreciate that, but, it seems that I learned more about my brakes than I did car control. Perhaps I am wanting more than the instructor fee purchases. Additionally, running with the nannies on would build false confidence, would it not?
On the other hand, I understand why an instructor would prefer to have them on, but talk with a guy and give him a chance! I have a few years of experience autocrossing, and have some reasonable car control. I'd prefer to run with the nannies off so I can learn more!
I am glad to know this has been experienced before, thank you for posting your experience. I didn't expect the rears to get that thin in just 2.5 days, they were nearly metal on metal at the end of the weekend, but, even on day 1, the pedal was getting long. I agree, it's clearly heat from having the nannies on. I can't imagine the rears building that much heat otherwise.
With regards to the dust boots, those were melted at an autocross, by the prior vehicle owner. There didn't appear to be new damage this time out, to the dust boots, just the pistons, pads, and presumably, the fluid.
With regards to the instructor, I wouldn't say I am throwing him under the bus. This was the first instructor that had me run with the nannies on (of 3). At the end of the weekend, he wrote down that in his opinion I should be solo, and I appreciate that, but, it seems that I learned more about my brakes than I did car control. Perhaps I am wanting more than the instructor fee purchases. Additionally, running with the nannies on would build false confidence, would it not?
On the other hand, I understand why an instructor would prefer to have them on, but talk with a guy and give him a chance! I have a few years of experience autocrossing, and have some reasonable car control. I'd prefer to run with the nannies off so I can learn more!
That's my opinion, but, I am just learning.
Once a student displays a satisfactory level of basic car control (knows and anticipates over/understeer dynamics and thinks ahead, taking corrective actions) and responds to instructor suggestions, all driver aids should be off so the learning can begin.
I saw nothing in your video that would have made me insist on AH for your sessions. Sheet, anyone ready to solo at Homestead should be competent enough to run without the driver aids.
Like many here, I've been doing this long enough to have learned in high powered cars that did not have any electronic driver aids, not even ABS. Respect and a little bit of fear and self preservation are two of the key elements I look for in an advancing student. I'm in the camp where the driver aids are turned off unless the track is wet.
I instruct and I would be pretty happy with your performance from what I saw. Maybe a hand placement once but that was a pretty solid lap if you are still in group 1 (soon for solo). If you were at a tight track I would have possibly recommended traction control but on a huge track like a NASCAR track not really a need. You obviously have the line 90%. You need to be soloed and start working on your own with traffic. Seems the same, but most def is not.
Good job though. What tires are you running (unless I missed it)?
Thanks for taking the time to review the video and help with the cause of the brake issue. From the look on the front rotors (uneven pad transfer), and the brake feel (long pedal). it appears that the calipers may be spread.
I am running RS3s, 255/285 on the stock wheels and love these tires. I wish they made them in 315.
01-08-2015, 08:46 PM
Have you ever seen this (deformed caliper piston)
