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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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