Re: Re: Report--Call to RPI Re: Wilwood brakes

["Smith, Kirby A" <kirby.a.smith@lmco.com>]

Andrew Buc <abuc@ibm.net> asked "Gary G. Erickson"
<erickson@teleport.com> via the list:
             
"Your thoughts on drums vs. disks for street use?"

I can't resist a gratuitous historical perspective.

Drum brakes are significantly less prone to corrosion damage.  They tend
to stay dry and constant in their performance in wet weather.  They are
self actuating, on one side, and make vacuum assist optional.  Assuming
that proper sintered-metallic shoes are fitted, drum brakes can handle
spirited road driving as well as mountain descents.  They were used for
years by NASCAR before disks were homologated, including during the time
that road races were part of the tour.  

Drum brake shoes in use during the late '60s had larger friction contact
areas than even the most heroic disk brake pads.  I suspect that drum
brakes are more efficient as a result of this in making very sticky
tires operate at the threshold of excess slip.  However, disk brakes are
easier to cool, and are therefore better for extended races (over a few
laps) because the shoes will eventually heat up, and there is no easy
way to get air to them without opening holes in the backing plate, and
thereby defeating the main advantage for street use - protection from
corrosion.

I suspect that drum brakes are intrinsically lower in cost.