Ok my friends are telling me that their aftermarket cross drilled and slotted rotors give them better stopping power. For some reason that sounds wrong to me. I could see how the rotors would get rid of heat quicker but cross drilled/slotted rotors have less metal for the pad to grip. Which in turn should equal less braking power, or if not less then certainly their would no gain in stopping power. Could someone help clear this up for me and let me know am I right or wrong?

Thanks

 

I think the cross drilled and slotted rotors look good and are slightly lighter but not worth the money for the street.

The cross drilling was a solution to the problem of pad outgassing. The pad material would heat up and cook out a gas that would try to lift the pad off of the rotor surface. The holes provided a vent into the air flow from the center of the hub to the edge of the rotor. With modern materials, that pad outgassing doesn't happen anymore, so no point to it.

Cross drilling produces stress risers at the holes, that means rapid cracking of the rotors and early replacement.

I see no value to the slots at all.

I have done no testing, but I am convinced enough to be installing 13" C5 brakes with no cross drilling or slots. The directional vents in the center of the disk between the wear faces are an improvement. They make the rotor a better air pump and help with cooling.

Like splitfire, all marketing hype.

 

Modern pads do outgas, but not like in past years. Race cars and serious competition vehicles still use cross drilled rotors because every bit helps. But for those of us who drive on the streets, you won't really notice a difference. A friend and I did testing using a 91 Vette. With the pads cold, there was no difference. When they got hot the drilled rotors (on average) were a few feet better. The best bang for the buck came from Napa ceramic pads. These reduced the stoping distance almost 15 feet.

Bottom line, they look cool. But at upwards of $150 EACH (and you thought dealer prices were high), I've got better things to do with my money.

 

I haven't seen any race cars using drilled rotors. Porsche might be the only one I could imagine, but I doubt that as well. Slotted rotors, sure, almost everyone uses them. It heats the pad up quickly and keeps it from glazing. But not drilled. Any more, that's just for looks unless the car is overbraked with solid rotors.

By the way, none of this has anything to do with stopping distance - it has to do with getting the car's energy transferred to heat in the rotors, which are then cooled - hopefully by the time the next turn comes around.

Dave

 

I disagree with you. You're right about the transfer of energy, but, brake pads do off gas. That's why slotted and drilled rotors perform better when heated up.

 

Here is some good reading on the subject.

http://www.baer.com/Support/FAQ.aspx#1