[DeTomaso] Wilwood Brakes WTF????

[Scott Bell]

Mike,

Couple things, if the rears had little wear then the system is not balanced. Of course, that has nothing to do with the front issue.

Are the front pistons the same size or are they staggered piston calipers. If they are the same size, the problem you experienced is
common. This is why they have staggered piston calipers and 6 and 8 piston units.

I believe you are driving past the capabilities of the current system. 4 piston non-staggered calipers are fine for the street but
for the track, they are entry level at best (in my opinion). Sure, there could be some mechanical issues such as a stuck piston or
air in the system, etc... but since the issue is consistent across both sides of the car and across both pads in each caliper, I
believe you have exceeded the capabilities of the current system.

I would strongly consider upgrading to 6 piston calipers and also evaluate why the rears are not matching the fronts from a
wear/performance perspective.

Scott

-----Original Message-----
From: detomaso-bounces at poca.com [mailto:detomaso-bounces at poca.com] On Behalf Of MikeLDrew at aol.com
Sent: Sunday, April 14, 2013 2:08 PM
To: detomaso at POCA.com
Subject: [DeTomaso] Wilwood Brakes WTF????

Hi guys,

So, you may recall my description of me beating the snot out of my Pantera 
at Laguna Seca a couple of weeks ago.   I had a super, super time!

Partway through the second session, I started to get some juddering in the 
steering, from the brakes.   I presumed that the cheapo rotors had warped 
slightly, but I was able to drive through it, and then unwarped when the car 
cooled off.   I noted with some surprise that the front pads had worn down 
50% in just two 30-minute sessions while the rears looked perfect.   The wear 
was perfectly even.

I then had an uneventful three-hour drive home.   During one of my stops, I 
took the time to feel the wheels for any excess heat that might be caused 
by brake issues, and didn't feel anything untoward.

The next time I drove the car, I noted that the brakes were definitely 
sticking (or at least, SOMETHING was sticking).   I could drive down a gentle 
slope, put it in neutral and the car would gently come to a stop.   Obviously 
not right.

Today I jacked up the car and pulled the wheels, and was shocked at what I 
found:

http://www.poca.com/index.php/gallery/?g2_itemId=39244

http://www.poca.com/index.php/gallery/?g2_itemId=39260

Both brakes were clearly stuck on, with the pads badly tapered and worn 
within microns of bare metal on the bottom sides.

Since I have 2 psi residual pressure valves in the system, I thought that 
perhaps the front one had failed and stuck on.   If that was true, then it 
would act almost as if somebody was stepping on the pedal.   To test that 
theory, I cracked a bleeder on each caliper, expecting brake fluid to jet out.

Nothing.

So the problem is more mechanical in nature, rather than hydraulic.   I bit 
the bullet, pulled the pads and then removed the passenger side caliper.   
The pistons were very, very difficult to move within the caliper; I managed 
to compress one almost all the way before wising up to the fact that it 
would be almost impossible to remove if it was flush.   The other three came out 
with some work, that first one came out after a LOT of work.

The rubber seals inside the calipers look and feel just fine--having said 
that, I don't exactly know how they are supposed to feel, but they are soft 
and pliable.   The pistons were covered with brake dust, but a few minutes 
spent with brake cleaner and a rag, and some emory cloth, and everything 
cleaned up perfectly.

http://www.poca.com/index.php/gallery/?g2_itemId=39251

So, the question is, what caused this?   Could excessive heat have caused 
the pistons to expand and swell and jam in the caliper?   Not what I would 
expect from 'racing brakes', and the pedal never went even slightly soft, so 
it's not as if the fluid was boiling.

Does anybody have any other theories as to the cause?

And more to the point, what should I do now?   I suppose since they are 20 
years old, and apart already, I should probably buy new seals (or new seals 
and pistons?) and swap them out before reassembling everything.   But this 
still begs the question--why did this happen????

Looking forward to words of wisdom (along with inspired wild-ass guesses!)

Mike
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