Slotting vs. Drilling (was: Brake upgrade for the '81?)

["Brad Sterling" <bgsterling@earthlink.net>]

<snip Scott>

> If you buy new rotors you might consider cross-drilled or slotted (I
> personally like cross-drilled).

Aside from looks, why do this? Slots are a decent way to vent the gasses
generated under heavy braking. However, drilling removes a fair amount rotor
surface area. I'd run standard rotors or go slotted for best performance.
<end snip>

>From a different list.  Thought it would help.

<snip other list>
I thought I would have a word to my brake development contact at AP Racing
to get their view on the subject of drilled versus slotted and the answer he
gave is below

Holes are used for race use. For race use AP Racing believe them better than
grooves. They are there to outgas the pads when they get to very high temps.
The draw back to holes is they raise stress raisers and can be prone to
cracking when abused. The holes should always be chamfered and should not be
just drilled any where. The reason AP Racing supply them for road use is
because the car manufacturers like the 'race' look.

Grooves are for road use and are designed to 'scrape clean' the pads to
remove the degraded pad material which accumulates on the pads under normal
driving conditions. They are a 'fade preventive' measure as opposed to
raising the point that fade occurs. i.e they make sure the pads are
operating at their maximum efficiency as opposed to holes which raises the
fad point by allowing the outgassing.

Obviously to get the ultimate performance of drilled discs you need to use
race pads whereas grooved discs are designed to be used with road pads.

So I guess for road use as long as you purchased the disc with either holes
or grooves in they will be ok. If you buy plain discs to get modified then
drilling holes in them will be asking for trouble.
<end snip>


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