Guys,
I just finished talking with "Tim" at Porterfield in L.A. regarding their
brakes and thought maybe some of you would be interested in some of the
information I got.
Porterfield's pads come in three grades: R4, R4E, and R4S. R4 is standard
race and R4E is "endurance", which Tim claims has about 10% longer life
than R4, although he said it depends a lot on how the driver uses them.
Both the R4 and R4E cost the same. The R4S is the "street" version and is
less expensive. I told him I had run the R4S at the Streets of Willow and
thought they worked very well and his response was that for that track I
definitely should have been using the R4 or R4E because the track is so
brake intensive. I asked about oxidation of the pads at high temperature
and he said any pad will wear faster when it's hot, including the carbon
compounds. I tend to think especially the carbon compounds since after two
days of hard use, the front pads look pretty well shot, although they were
still working just as well at the end. It's probably comparing apples to
oranges, but the last time I ran there with DS-11 pads, they were still in
pretty good shape when I left. I asked about the "carbon-Kevlar" versus
"carbon-metallic" terminology and Tim says that Porterfield's pads have
carbon, Kevlar, and metal included in the compound. True "carbon-metallic"
pads are the exclusive product of Performance Friction which supplies these
pads for Indy, NASCAR, etc.
If you are interested in ordering these pads, or have further questions,
you can call Porterfield at (800)537-6842 or, from California,
(714)548-4470. The cost for a set of front pads (240Z application) of the
R4 or R4E type is $65. I have the Fiat rear calipers and these are more
pricey; $110 for a set. The street versions are cheaper, but I didn't get
a quote. The pedal pressure required for the R4 & R4E is less that for the
R4S, so this is a consideration in how to match up front and rear. If you
have standard rear drums, you can also get shoes with these compounds; at
least they are available from Dale's Restorations so maybe also directly
from Porterfield. Prices direct from Porterfield are understandably
cheaper than through Dale for the front and rear pads. I'm guessing that
the R4E takes a little more pedal pressure than the R4. I tried to get an
answer to this question from Tim, but he wasn't clear. Probably not much
different (10%?). I wondered why they would bother with a pad that is only
10% longer lived and his answer was that for a four hour enduro it might
make the difference. Doesn't sound like it makes enough difference to
matter to most of us, however. Tim also said that some people do use the
R4 on the street and there is no problem in terms of rotor wear, hot versus
cold, etc. In street use you can probably expect to get maybe 8k miles of
use which, depending on how much you drive, could be a lot or a little.
While I was at Willow I talked with Dan Walters about his experience with
Porterfield brakes. Dan is critical of Porterfield for inconsistent
quality. He claims you don't necessarily get the same thing every time and
that even the appearance of the pad material varies a lot as well as how
they work. Dan favors pads made by Hawk (sp?). Don't know anything else
about them; you'll have to find out from Dan. They offer two compounds
which are color coded and, therefore, are easily recognizable. Dan says
he's not the only one that has found the Porterfield brakes to be
inconsistent. However, to be fair, I would say that there are a lot of
factors, both subjective and objective, that affect brake performance, so
this anecdotal information should probably be taken with some skepticism.
I ordered R4 pads for the front and rear. I'm anxious to try them and
compare with the R4S. The rear R4S pads actually still look in relatively
good shape and were apparently not getting as hot as the fronts.
Obviously, if I intend to do more really intensive braking I'll need to get
some better cooling to the front brakes. Right now there's nothing special
done for ventilation except remove the rear disk cover. The rear disks
dissipate more heat to the aluminum rims - they get considerably hotter
that the front rims - which may partly explain why the rears faired better
than the fronts. There is also the issue of balance. The front brakes
were, I believe, locking up first. This is good, but not if the rears lag
too far behind. Don't know just how much more braking out of the rears I
could have gotten before they would have begun locking up first. Ideally,
I guess you'd want them to be in the 90-99% range for optimum braking. I
have the impression that with the same pad compound and no proportioning,
the Fiat rear disks are still pretty conservative (75%). After settling
some bigger issues, I want to explore just how much more bite I can get
with the rears before they start locking up first, then back off slightly.
Bob Palmer
UCSD, AMES Dept.
rpalmer@ames.ucsd.edu
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