cross dressed Scott Williams is YOUR DADDY!

[scirious@hotmail.com (Brian Haygood)]

Oh yeah, you were thinking pressure.  F=uPA.  Now I get it.

BH
----- Original Message -----
From: Aireq <trance_whore@yahoo.com>
To: Brian Haygood <scirious@hotmail.com>
Sent: Saturday, March 23, 2002 4:43 PM
Subject: RE: cross drilled Scott Williams is YOUR DADDY!


> Shit no your right. If it was Normal force per unit area I'd be right, but
I
> forgot that the same normal force would be spread out over a bigger area.
>
>
> What the hell are we all talking about anyway? Who here ever wants to slow
> down, I thought this list was about making our cars faster ; - )
>
>
>
> eric
>
> -----Original Message-----
> From: Brian Haygood [mailto:scirious@hotmail.com]
> Sent: Saturday, March 23, 2002 3:11 PM
> To: aireq@u.washington.edu; scirocco-l@scirocco.org
> Subject: Re: cross drilled Scott Williams is YOUR DADDY!
>
>
> Your equations says that bigger brakes have more stopping power per unit
> normal force.  It doesn't say that your car will achieve a shorter
stopping
> distance than it otherwise would because your wheels will lock up when the
> same equation limits traction between your tires and the road.  Unless you
> overcome that weakest link, then you will never have a use for that extra
> stopping power, in just the same way you never use it now.
>
> Now the real question is how you managed to pull that equation out of your
> ass.  The friction force is not proportional to the surface area.  F=uN,
not
> F=uNA.  Now this equation is an estimate as well, and is really only
> accurate so long as the yeild strength of neither of the parts in contact
is
> achieved (give or take).  This is why more rubber on the road means more
> traction, because the tire crumbles just like a pencil eraser before it
can
> transmit its maximal force dictated by its static coeficient of friction.
> But even this relationship is generally miles away from creating a
> proportional relationship between surface area and friction force.
>
> The larger area means the same amount of energy can be dissipated with a
> smaller increase in temperature over a larger mass of metal.  So they
don't
> heat up as much.
>
> The disadvantages of larger brakes, including increased vehicle weight,
> increased unsprung weight and its associated traction loss, increased
> rotational inertia and its acceleration/deceleration losses, have already
> been discussed in this thread, so I don't think we need more words to say
> that if there isn't a strong need for bigger for heat reasons, then
smaller
> will be better.  Again, we have to realize that these are lightweight
cars,
> and therefor react more poorly to an extra pound of unsprung than the
> heavier A4's and such.  Heat can also be reduced with vented rotors, which
> usually (IMO) offer weight or rotational inertia advantages over their
> larger rivals that could handle the same amount of energy (heat).
>
> There is a bit of friendly ribbing in there, and I hope it is taken as
such.
>
> BH
>
> ----- Original Message -----
> From: Aireq <trance_whore@yahoo.com>
> To: Scirocco Mailing List <scirocco-l@scirocco.org>
> Sent: Saturday, March 23, 2002 3:36 PM
> Subject: RE: cross drilled rotors Scott Williams is WRONG!
>
>
> > F = uNA
> >
> >
> > Force of friction is equal to the coefficient of friction, times the
> normal
> > force, times the surface area. Bigger breaks will stop faster. Simple
> > physics. But the question is where the trade off goes the wrong way in
> terms
> > of weight added vs stoping power.
> >
> >
> > aireq
> >
> > -----Original Message-----
> > From: scirocco-l-admin@scirocco.org
> > [mailto:scirocco-l-admin@scirocco.org]On Behalf Of ATS - Patrick Bureau
> > Sent: Saturday, March 23, 2002 10:47 AM
> > To: Brett Van Sprewenburg; scirocco-l@scirocco.org
> > Subject: RE: cross drilled rotors Scott Williams is WRONG!
> >
> >
> > Bret I would agree for road vehuicules and daily drivers, coudl you
> explain
> > why then F1 Racing and Nascar Use Cross drilled rotors if indeed it
> provide
> > "now-adays" no evidance of added performance.
> >
> > inquiring mind would like to know.
> >
> > ATS - Patrick
> >
> > =>-----Original Message-----
> > =>From: scirocco-l-admin@scirocco.org
> > =>[mailto:scirocco-l-admin@scirocco.org]On Behalf Of Brett Van
Sprewenburg
> > =>Sent: Saturday, March 23, 2002 12:12 PM
> > =>To: scirocco-l@scirocco.org
> > =>Subject: RE: cross drilled rotors Scott Williams is WRONG!
> > =>
> > =>
> > =>>Hehehe that got your attention ;-)
> > =>>
> > =>>I don't know about performance, I think everyone is missing the
point.
> > =>>Rotors have holes drilled into them in order to increase air flow,
> > =>>thereby reducing heat in hard driving conditions (such as racing on a
> > =>>track). That's the theory behind that. I would say (not from
experience
> > =>>since my car isn't done) that they would work...It just makes sense.
> > =>>Will this increase performance? I don't know, but I do know they
would
> > =>>have to be cooler (temp) no? Of course it could take a couple of
> seconds
> > =>>for the pad to grab the cooler rotors (so I've heard). That's why you
> > =>>would want to get the braided lines to get a better bite in the
> > =>>caliper...As far as Scott being wrong, I think I have a better chance
> on
> > =>>finishing my car today than proving him wrong...
> > =>>
> > =>
> > =>I really need to post that brake article... :)
> > =>
> > =>Anyway,  I'm afraid the above opinion is incorrect.  I'll paraphrase
> from
> > =>the GRM brake article again...
> > =>
> > =>Crossdrilling your rotors does nothing in most situations
> > =>now-a-days,  except
> > =>look cool...so please don't say it's for higher performance. (And
> > =>they do look cool) ;)
> > =>
> > =>Rotors were first drilled because early brake pads from the 40's
> > =>and 50's gave
> > =>off gases when heated to racing temperatures.  The gasses then
> > =>formed a thin
> > =>layer between the brake pad face and the rotor, acting as a lubricant
> and
> > =>lowering the coefficient of friction.  The holes were implimented
> > =>to give those
> > =>gasses someplace to go.  Todays friction materials generally do
> > =>not exhibit
> > =>the same gassing out as the early pads.
> > =>
> > =>The holes have carried over more as a design feature than a
> > =>performance one.
> > =>Contrary to popular belief, they don't lower temperatures.  In fact,
> > =>by removing
> > =>weight from the rotor, they can actually cause temperatures to
> > =>increase a little.
> > =>These holes create stress risers that allow the rotor to crack
> > =>sooner, and make a
> > =>mess of brake pads - sort of like a cheese grater rubbing against
> > =>them at every
> > =>stop.  Need more evidence?  Look at NASCAR or F1.  You would think
> > =>that if drilling
> > =>holes in the rotor was the hot ticket, these teams would be doing it.
> > =>
> > =>Ok, let's debunk the bigger rotors = better here also (again).
> > =>
> > =>Bigger rotors will make your friends think you are cool, bigger
> > =>rotors look sexy, but
> > =>bigger rotors do not stop the car.  What a bigger rotor will do is
> > =>lower the overall
> > =>operating temperature of the brakes - which is a GREAT idea IF your
> > =>temperatures
> > =>are causing problems with other parts of the braking system. (It can
> > =>also changes how
> > =>the brakes are modulated by the operator, which might be better
> > =>for them).  The
> > =>quick motto is bigger is better until your temperatures are under
> > =>control.  AFter that
> > =>point, you are doing more harm than good due to the load of steel
> > =>hanging on the
> > =>wheel that needs to accelerate each time the gas pedal is pushed.
> > =>
> > =>Finally, SS brake lines only remove compliance from the braking
> > =>system, which really
> > =>affects only the pressures and forces applied, not so much how cool
> > =>the rotor is
> > =>running...
> > =>
> > =>Again, this is an excerpt from a rather extensive braking article
> > =>from Grassroots Motorsports,
> > =>written by an anti-lock braking systems engineer with the Robert
> > =>Bosch Corporation who
> > =>is a Saturn racer for scR motorsports.
> > =>
> > =>In my opinion, this probably doesn't matter to the most of us
> > =>anyway...very few of us
> > =>are pushing are cars hard enough to get into the perfomance areas
> > =>where these kinds
> > =>of details actually make a difference very often.
> > =>
> > =>==Brett
> > =>
> > => \/  '84 Scirocco (ITB racer 2B) | "Hot VW's, take two home.
> > =>They're small"
> > =>\/\/ '88 Scirocco 16v (Show), '92 Passat 16v (Winter+) | -
> > =>brett@netacc.net
> > =>
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> >
> >
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