while it is true that slotting has become the more common method of improving rotor performance, and cross-drilling was something originally intended to combat heat with asbestos pads, there is plenty of data out there to show the improved braking from drilled rotors, particularly in the wet.
further, they do not always crack. that is almost always due to either a poor job of the drilling, or due to incorrect pad choice. as an example, i have had the same set of zimmerman cross-drilled rotors on the blue car, and there is not a single crack or hint of one, even though there is significant rotor wear.
the amount of surface area removed is minimal, and it is only contact surface. the cooling surface is actually increased. the improved cooling outweighs the contact loss. the additional exit paths for the heat and gasses is significant. again though, these need to be done right, and used with the right pad.
done correctly, cross-drilled rotors do an excellent job. done wrong, for example not having overlapping patterns, or lacking chamfering, can result in uneven wear and cracking. using a pad that does not dissipate heat well will do that too. the pads and rotors have to work together.
guys who tell you that cross-drilling doesn't work are frequently the ones who choose the wrong pads or cheap rotors. i hear this sort of thing all the time, but never from anybody who has actually tested them back to back.
as for slotted rotors and pad wear, it can go either way. it really depends on the pad type. it is a bad idea to use a soft pad on a slotted rotor, as it will wear quickly. a hard pad will not. as an example, the denali comes with solid rotors and soft pads and gets on average 20k miles on a pad set. with the cross-drilled and slotted rotors i have now, and the porterfield 4S pads, i get over 40k miles on them. they also don't fade or get nearly as hot.
one thing that either cross-drilled rotors or slotted ones do that solids don't is resist deposits that make for uneven braking and brake fade. the uneven surface helps to scuff the pads continually, thereby reducing that tendency.
i've run them all. i've tested braking distances. i'll continue to run anything but solid rotors on any car i intend to drive fast, or expect maximum braking from. as soon as the white car wears out its brakes, i'll upgrade that one too.
we are now WAY off track.
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