gapboi210 said:
On a lot of the late '90's and early 00's GM sedans were very prone to warping the rotors very easily. Afte the upgrade customers never had that problem again/ And I don't think you can compare Nascar to a 4Runner. They have air ducts directly on the brakes. The cross-drilling does help keep them cooler and remove water and debris through the slotting
Mmmm, Gen II 4Runners hace air ducts that point directly at the brakes.
Crossdrilling does NOT make 'em run cooler and was never designed for cooling.
The original use for cross drilling was to provide a way to let the gas that the pads produce escape instead of building up as a layer between the pad and the rotor.
Pads no longer outgas at least in the temperature range that they even come close to seeing in out applications.
NASCAR can be looked at.
If crossdrilling was required for cooling and/or outgassing it would be done.
It's not.
NASCAR cars need all the brake cooling that they can get. If crossdrilling helped in any way at all you can bet your butt that they would be running crossdrilled rotors.
I've invloved with Sprint cars and we use a solid (vented) rotor. No crossdrilling at all.
They use a singe rear, inboard rotor that can reach temps in tht 1000* range. If crossdrilling helped in any way you can bet they'ld be on the cars.
Here's a photo taken (at night) of a rotor on a Sprint just as it pulled into the pit area. This is a color photo, and yes, the color is correct. It's not glowing red hot. It's well past that and is white hot.
You search up and figure the temperture that cast iron has to get before it reaches white in color.

Fred