Paint color won't have much effect at all on heat dissipation from brake
drums. Most of the heat generated is conducted through the various metal
parts and out to the outer surfaces where convection cooling takes place.
The most effective thing(s) you can do to improve cooling (which will
improve braking and reduce fade) is to use drums with finned surfaces. This
will dramatically increase the surface area for convection cooling (air
passing over the surfaces). A secondary improvement is to use drum material
that has better thermal conduction coefficient so as to better conduct the
heat away from the contacting brake surfaces out to the exterior surfaces.
Paint color will have only a minor, if any, effect because it is involved in
radiation heat transfer which is very inefficient at relatively low temps
(like room temp up to a couple hundred degrees F). For radiation cooling to
be effective, you typically need very large temperature difference between
the emitting surface and the absorbing surface (which would be things in the
surrounding environment).
Paint your drums whatever color suits you.
Roy
'60 TR3a TS63103LO (in restoration)
techman@metrolink.net
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