Braking Technology and experts....
QSHIPQ at aol.com
QSHIPQ at aol.com
Tue May 14 09:15:23 EDT 2002
I'm gonna chime in here Michael. First, experts are ascribed, not claimed.
Whenever I hear anyone in motorsports speak of being an expert, I tend to
wince. I've met and discussed motorsports with many experts, never heard
*them* ever claim to be. You did, why? And, IF you want to claim being one,
boy have I got some questions for you!
That said, you have a lot of btdt wrt porsche application calipers. Your own
website and "expertise" appears to be full of porsche application
calipers/rotors. A lot of btdt on them, if you put 50hours a week into them.
I do notice too, that you don't routinely change the piston seal on a
"rebuild", which to me, means you missed *the key* part of a caliper rebuild
(well along with putting in new pistons). What are you "inspecting for"
I'm *NO* expert, don't claim to be. And, what I find, is that ANY discussion
in a public forum wrt techniques, math, documentation or btdt gets a high
calibre return fire from you, never discussion nor "answers". My reference
to humble pie was in regard to your last years post on A8 rotored Big Reds -
a bad math problem. When you present strong "opinions" you *should* expect
to be taken to task, "right" and "wrong"? From my research, the best *any*
expert can claim is "better" and "worse". You want to go "stronger" than
that? Ok, best of luck, you have already been taken to task by the currently
available documentation. What we should be spending your "expertise" on, is
discussion on the development and measures of critical issues wrt brake wear,
construction, and heat measure. A LOT of information is available to any
novice or "expert". There is no magic here, the factors that affect brake
performance and service life are well known. Anyone putting together Porsche
street rotors with adapter hats, isn't enough anymore ('old hat'?:) - to be
Michael, when you come to these quattro lists, we don't need any reminder of
our substandard brakes. Many of us understand not only that they are
substandard, but *exactly* what makes them so. Your business revolves around
the Porsche\Brembo calipers and Porsche rotors. What your "expertise"
appears to be lacking is detailed knowlege of construction and the effects of
heat and application on them. That's ok, you are hardly alone, only recently
has computer modelling been able to isolate the many variables in
caliper/rotor construction vs heat.
What this does mean tho, is that your "porsche" applications may be better
than what was at the factory for a porsche, and it may or may not (and your
self proclaimed expertise might not) so "simply" apply to audi cars. Right
now, the modelling and measures are just starting to isolate the variables
that affect the major goals one wants to control in any caliper design:
Piston Retraction, Seal contruction/groove design, Minimum piston travel for
a given design, bridge heat, caliper distortion/carrier distortion, pad
construction vs distortion and the effects all these variables have wrt the
additional stress of heat cycling. If you do intensive study on the
available documentation, all these variables are getting isolated 1 by 1,
slowly, AND using heat = constant, and piston caliper as a given "rigid"
design (t = constant, no heat distortion factors yet).
What you can find in all this data logging is blaring indications where the
focus is in terms of variable isolation. First a foremost is piston
retraction and drag torque. The variables that affect those 2 critical
factors are piston and seal design/groove design. The quandry facing all
engineers wrt these factors are the apposing goals of piston retraction vs
reduced piston travel. Again, these are just now being isolated in the
"virtual model" (vs testing actual calipers on specific cars), and heat is a
constant in these models (which we know is far from the truth).
All that said (nerd hat on), what you do find is some interesting data
appearing, which would indicate that reduced piston travel is a desired
trait, and that the further you can isolate the piston from the rotor over
the life of the pad, the lower the heat transfer into the piston and caliper.
In the "rebuild" business, maybe an oxymoron... Enter the "shim"
IME/O porsche has one of the best, my toyota 4 runner maybe even better.
Porsche uses a heat reflecting shim behind the brake pad of 1.5mm, and is
quite a nice piece of metal, considering it's actual function. My 4 pot
toyota on the other hand, uses 2 shims per pad, one a thin heat reflector,
the other a thin grate type piston heat isolator. I'll take either one,
since the effects of worn pads wrt heat (read increase service/damag) is
documented to dramatically increase. By as much as 50% with a non SM pad in
fact. More with SM.
I'd personally love to get Keith Maddock involved in a more in depth brake
discussion, since he does this for a living at TRW, and may have access to
the "latest" trends. That said, what some of us have done, is taken to heart
the available technical data, and apply it to street cars. Right now, I've
serviced a lot of non booted calipers that have lasted longer than booted
ones (for a variety of reasons). I've serviced a lot of booted calipers that
haven't lasted 1 run group at RA. So, to me the debate isn't "which is
better" cuz those variables haven't been really isolated yet (only
"claimed"). The common goal should be how to keep distortion and heat
transfer to a minimum over the service life of a given braking system.
The most obvious way, is to keep the piston away from the rotor. In my
simple world, I haven't seen an argument yet that seems to discount that
target. I'm happy to discuss in depth (on any list;), the cutting edge
technology wrt braking construction and design. CLAIMING by "expert
testimony" that what you do is right, and others wrong, just seems premature
to me. Especially, when we can look at a million G60's, and know what is
"wrong". Which makes what is "better", even include a cheap ass motorsport
unbooted wilwood with shims. Which is RIGHT? With all due respect Michael,
you haven't supported that yet.
You have made your opinion on brakes pretty well known. I disagree with many
of them, and am happy to go thru the available documentation that would
support my reasons why. Attacking me for that disagreement, turns a
discussion on brakes, into personal attacks. I encourage you to get beyond
that. Since brake designers haven't been able to answer a lot of the
questions wrt what is "right" in production applications, all bets are off in
the aftermarket designs. Which makes your opinions, just that. When many
look at your "expert testimony" posts, you have listed RIGHT and WRONG ways
of doing things. Quite frankly those are pretty strong statements for ANY
expert to make. And not supported.... Yet.
Stick around, though I suspect a summated understatement would be: Heat is a
QSHIPQ Peformance Tuning
T44tqw mit big reds and shims
In a message dated 5/13/02 4:52:15 PM Central Daylight Time, igor at s-cars.org
"Michael (Prospeed Motorsport)" wrote:
> I'm outa here . . . Every time I try to offer some expert help on brake
> systems and the right vs. wrong way of doing things, someone takes to me
> to task.
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