Re: drilled rotors and cooling

[Richard Welty <rwelty@domain.elided>]

On Sun, 20 Oct 2002 20:08:20 -0700 Joe Martin Cantrell <agiyo@domain.elided> wrote:

> Far be it from me to contradict (and I'm not) our esteemed Mr. Welty,
> but I 
> have some recent research from the Institute of Empirical Blunders.

> Last weekend's AROO track day was the first at-speed test of my drilled 
> rotors.  I bought them a couple of years ago, before I read that you
> need 
> slots to cool brakes and drilling in itself does not help cooling.

> I brake into the turns very late, and had problems with fade,
> incrementally 
> alleviated by fitting AXXIS semi-metallic pads and 600F degree brake 
> fluid.  The situation had gone from virtually no brakes after the second 
> session of the day, to "I wish these were a lot better, but I'll
> probably 
> make it or spin."

ok, fine. but there's fade, and then there's fade.

"true" fade is caused by material buildup between pads and rotor
surfaces, it has nothing to do with heat. either the pads are
outgassing (usually green fade, the pads are new and boiling off
material) or else the friction material is simply not getting out
from between the pad and the rotor surface.

in this case, drilling or slotting can help. it has NOTHING to do with
overheating. NOTHING AT ALL. this kind of braking failure feels like you're
pressing hard, and nothing is happening.

heat related failures are generally fluid becoming compressible inside the
caliper body. they have a completely different symptom; when you depress
the brake pedal, it feels mushy and ineffective.

do _not_ confuse heat related failures with failures caused by material
buildup, they have different causes and different cures.

Fred Puhn's _Brake Handbook_ covers this in comprehensive detail. don't
take my word for it, go read a reference by a real expert.

richard
--
Richard Welty                                         rwelty@domain.elided
Averill Park Networking                                         518-573-7592
              Unix, Linux, IP Network Engineering, Security
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