cross drilled rotors Scott Williams is WRONG!

[brett@netacc.net (Brett Van Sprewenburg)]

>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