Rick (zrol01@trc.amoco.com) writes:
> The point here is that the disk rotors on the Jag XJ-S that I
> am building are vented. That is, they are really a machined
> casting of two parallel rotors with cast "spokes" between them.
The majority of my brake experience has been with honking big G.M.
cars, which have the same vented design. As the wheel turns, there
are always several vents open to the incoming slipstream, and when
everything's stationary, air can percolate vertically up through
the rotor.
> Again, the idea is cooling. The "shields" fit neatly around the
> inside of the rotor with no flares on the perimeter. However,
> they do have an aircraft type air scoop that delivers air to the
> axis of the rotor presumably where the openings to the "spokes"
> begin.
Bingo. There's been some in-depth discussion over in the Mustangs
group on how to enhance cooling in that area, and someone recently
announced copies available of his plans for fabricating an air duct
from sheet metal to do just that.
> I assume that any protection from gravel, etc. lodgeing in the
> the caliper is just a by product as pretty large gravel could
> be sucked into the scoop.
As the brake pads are pretty much in contact with the rotor at all
times, they would skim off large particles without allowing such grit
to wedge itself between rotor and pad anyway. Flying grit could ping
itself off the spinning rotors all it wants; the polished metal is
hardly conducive to letting anything stick to it, so I don't think
the shields would be needed for that purpose (and again, there is that
matter of the front-aimed open scoop on the shield on some cars...).
I suppose that those cars which did not come supplied with shields
were found to not need any help with brake cooling, for whatever reason.
-- Andy
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