Food for thought (Re: UFO Brake Conversion)

[Luis Marques <marques@rtis.ray.com>]

Could the reason for UFO brake warping/overheating be inherent to their
UFO design?  Any rotor has to be able to perform two duties: absorb heat
when braking, and getting rid of it afterwards.  The first part the
UFO's must do quite well, since they have good mass (heavy!) and swept
area, but I don't think they are very efficient at getting rid of the
heat.

A traditional rotor gets rid of heat three ways: by radiating infra-red
energy, by conducting heat to the air, and by conducting heat to the
hub/wheel.  By having the rotor contact the hub from the outside instead
of the inside, I think the resulting "UFO hat" will block much of the IR
radiation from the outside swept surface (can you say heat shield?). 
Also, the air flow on this outside swept surface must suffer.  Finally,
by going the long way around from the outside of the rotor to the hub,
there will be a higher temperature rise from the hub to the swept area
due to the heat being conducted through the "UFO hat".

Traditional rotors (and "2-piece" in particular) should be much more
efficient at getting rid of the heat by effectively not having a heat
shield on the outside, better air flow, and must importantly, having a
direct path from the swept area to the hub resulting in very little
temperature rise as the heat flows to the hub/wheel "heat sink". 
2-piece rotors go one step farther and have an alloy center section for
even lower temperature rise and better heat flow to the wheels.

Just a little food for thought....  

Question: Guess what are Porsche and BMW M-cars using?

Luis Marques
'87 4kcsq