UFO conversion options

[Bernie Benz]

Hi Chris, good to hear from you.

Braking surface rotor corrosion I am not fimilar with but, from a materials
and operating conditions standpoint, I can not understand why the inner and
outer annular rings of the surface would be more suseptable to surface
corosion than is the center ring.  Any wild ideas?

As to the center annular ring doing all the braking, I don't believe it.
Apparently as you describe it, the rust is firmly attached to the base metal
of the rusted areas, possibly having a rougher surface and thus a
higher/different coeff. of friction against the pad.  If so, initial pad
wear in the rusted areas will be greater than in the center, but only
momentarily, until the contact unit pressure against the rusted areas is
reduced enough that pad wear is equalized in the two different friction
areas.  The total rotor surface is now equally effective.  Pad wear may be
greater overall because of the modified surface, the only negative IMO.

Cad, or even chrome plating the active rotor surface, IMO, would be a
waisted effort.  Cad is too soft, and both are too thin  <<.001" to provide
a lasting surface.  Better, select a more corrosion resistant casting
material for the rotor, but this apparently is not cost effective for the
mfgs.

Bernie



> From: C1J1Miller at aol.com
> Date: Thu, 26 Sep 2002 10:38:07 -0400
> To: 200q20v at audifans.com
> Subject: Re: UFO conversion options
>
> Bernie:  perhaps you don't have the same issue as those of us on the east
> coast.  Out here, the brake rotors rust, starting at the outer and inner edges
> of the rotors (also filling the vented areas; that's another issue entirely).
> The rust actually seems to creep in, get polished by the pads, then provide a
> poor braking surface (thus just the center 1" of the pads does the braking).
> It _looks_ like rotor surface, almost.
>
> On a car that's been sitting, a metal scraper can be used to remove this
> polished layer of rust off the outer/inner edge of each side of the rotor;
> might get you some more life out of the rotors.  Probably going to feel some
> brake pulsations, though.
>
> Cad plating new rotors might prevent this.
>
> Chris