> As far as cross-drilled rotors, I think that they are a solution to a
> problem that (for a street car) does not exist (pad outgassing) and
> their major benefit is cosmetic.
>
> Hugh Barber
I have been under the impression for many years that cross drilled rotors
having nothing to do with pad outgassing. The task of curing pad outgassing
should be handled through the use of gas slots, the slots break the surface
layer of gas that builds up under the pads and vents the gas to the outer
edge of disc. If this were the job of the cross drilled holes, they would
merely capture a small portion of the gas, which would be trapped in the
hole between the two pads until the rotor has rotated further... really not
effectively solving the problem of gas build up.
So, as I thought, the only reason for cross drilling is to dissipate any
heat build up in the rotor by allowing some air to pass through holes as the
rotor rotates. Not only that, but cross drilling increases the cooling
surface area of the rotor, because you have to account for the cylindrical
area that is now exposed to the air inside of each drilled hole.
As for the reason about why you can't resurface cross drilled rotors, it
most likely has to do with the fact that any major resurfacing is going to
remove a good portion of the countersink that is on either side of the cross
drilled holes. When you remove the countersink, your pads bite a rough
edge, which probably is what results in the pad kickback and bucking brakes
that other listers have mentioned.
You can buy TR6 rotors that either are solely cross drilled (eBay) or cross
drilled and slotted (most suppliers). I to agree though that they are
largely a poseur racing upgrade.
Kai
--
Kai M. Radicke
Wishbone Classics
www.wbclassics.com
Ph: 215.945.7250
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