Originally Posted by Raptor
Cross drilled rotors have proven to increase braking performance vs. solid rotors across the board on street drivin pass. cars.
The SAE did a very extensive study on the subject, you can look it up for yourself. Crossdrilling increased brake cooling significately vs the solid rotors. Only in racing
will cross drilled rotors begin to crack with crossdrilling. Not even with very spirited
street driving will quality manufactured crossdrilled rotors crack! I'm not referencing cheap e-bay cross-drilled rotors.... but hi quality blanks made to be cross-drilled allowing for proper rotor vane placement for cross-drilling with chamfered holes to reduce heat stress cracking.
Porche has never cast holes into any rotor they have ever made! That is an internet myth! They have always cross-drilled or machined their OEM rotors. Always.... ask them.
Really little boy. Provide cite for your claims on Porsche rotors??? Come on!
BTW I have installed Porsche rotors on 934s and 935s!
Now a rotor is a heat sink so the SAE paper you mention is wrong. Rotors were never cross drilled for cooling but Porsche cross drilled rotors for off gassing suggest you read Excellence Was Expected. At the end of Mulsanne before they pussified the track with chicanes Porsche drivers would hit the brakes and experience a momentary delay as the gases from the pads prevented the the pads from clamping the rotor.
Brake pad composition has evolved since the mid 70's. Brake pads rarely off gas today. Bedding in is still recommended.
If cross drilled rotors are so great how come NASCAR doesnt use them at tracks like Richmond, Martinsville, Bristol, Sear Point and the Glen??? NASCAR uses cast iron rotors and the teams would lobby for cross drilling if it would mean having brakes at the end of the race.
Sorry I have changed enough rotors on friends street driven vehicles to know that they can and will crack. These are vehicles that arent auto X'd or tracked.
Cross drilling removes mass which means the rotor can not dissipate heat as effectively. Brake cooling is done by running holes in the front of the car to which you attach high temp ducting. You then direct the ducting into the rotor and not across it. I spent well over a hundred hours doing brake testing
with brake temp paints, different fluids, different duct shapes etc at various tracks so I think I have a clue on how brake system works.
If you are going to Google something punk just dont look for BS that supports your lack of knowledge and experience.
Have a great day and please dont do any brake work for your friends!!!!!!
You might also read info from Raybestos, Wilwood etc on cross drilling.
Next we can discuss are the benefits of multi piston calipers worth money???
from Grassroots Motorsports:
"Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as "gassing out." ...It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads--sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it...Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the glazing often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)