I read (most of) the SAE paper and while it did suggest some improvements to braking performance it also left out the issue of premature wear and cracking that may come with that improvement. It covered the topic quite well and spoke of cooling effects etc and came to the conclusions that there were gains to be had. That being said I'd never suggest them for a track car.

Done so for their very best rotors...100% for marketing and bling. I don't know of one supplier mentioned that would push the use of drilled rotors for a track car without a huge red flag note of caution.


Re; that 10% (exact amount not important) increase in stopping power from the larger rotor....while the diameter will change the leverage of the equation final tire torque will remain the same. You won't get "more braking power" you'll only derive the same net torque from varying the input values. With a larger lever arm you will require less pressure to get to the same numbers.

Think of SKID as max torque. The skid will be the same point of lock up from any combo of pad Cf, greater piston area, more pressure, or larger diameters- the net skid remains the net skid. A 16" rotor over a 13" just means the calipers don't work as hard.

All that comes back to my comment last page: greater efficiency and lower duty cycle. To mean that more rotor won't work the pad and caliper as hard and be more efficient in heat transfer and thus the same net braking performance is achieved with less stress on the parts to do so. You could use an 8" rotor if you want to squeeze it hard enough but it won't hold up very long.

 

Cross-drilling is not a fad! It has been proven to increase braking performance for street driven applications across the board, do a search for the SAE report on cross-drilled rotors!

Now on to rotors with "holes cast in them". This too is pure misinformation. I challange you or anyone else to direct me to a rotor manufacturer that "casts" the holes in their rotors as part of the manufacturing process!! Complete BS!

All cross-drilled rotors are "machined or cross-drilled" after casting, none have holes cast into them. None! Every hi-end brake rotor manufacturer machines these holes into their rotors after casting!

There are cheap cross-drilled rotors for sale on E-bay that are mearly cheap solid blanks that have been cross-drilled "for looks" with no thought given too the thermal properties or structural integrity of the blanks. The holes in these rotors are often not chamfered and their quality along with their performance is complete crap! These cheap E-bay rotors should not be part of this discussion as there is no reason to even contemplate using them on any vehicle C4 or not!

 

I put C5 brakes on the front of my 1986 C4, and it stops like my C5, Period. I upgraded to C5 wheels, new tires, and an oh by the way, new front brake hoses as well. No grooves or drilled holes. (but if you want to send me some drill bits and a pattern, I have a dremel motor for the grooves...........)
Tire treadwear in fronts are 300, and the treadwear in back is 220. I tried to make the rears stickier than the front to invoke the abs a little sooner under hard braking.
Nothing wrong with the braking system from the factory, it has served me well. The old front rotors were 1/2 inch larger than the rears. THEY WERE ALMOST THE SAME SIZE!!!! The rears never wear out. i have had the car 12 years, and have removed the rear pads for inspection twice and they are the ones that came with the car. The rear rotors are nicely polished, and my fingernail cannot detect any surface grooves in the disc where the pad wears. They just look amazingly fresh. When I place my finger on the rear discs, they are hot, so I know they are used. Just not as much as the fronts. The front discs throw minute bits of pad material on the wheels and chew up the clear coat on the wheels. So why not make those brakes bigger, since they have to do the major portion of the braking effort? Why not have the fronts stop with less effort in an attempt to make the front brakes cooler?
In the land of 115 degree summer days, and 100 degree nights, it has become a concern. The rotors on a daily summer commute give off a tremendous amount of heat , it feels like the same or close temp of the exhaust manifolds. It is normal in the morning to hop in the car to go to work, and have the temp already reading 117 degres on start up because the garage can't cool down.
I just feel with all the new cars out there being able to stop in a shorter distance than me, i had to do something.
It's kind of like.......my 23 year old 245 horse TPI keeping up on the on ramp with a new 245 horse v6 in a spankin new malibu....gotta upgrade my standard of performance, regardless of the age of the vehicle just to be able to have the same performance level.
I put a ZZ4 and a 4+3 in my 57 Chevy pickup. now I have to make the thing stop cause it cruises at 75 mph with everybody else now.
At 1800 RPM!!!! in the previous days, it was 3400 RPM.
I got a dual master cylinder with a hydroboost and two piston calipers, 12 inch rotors and a complete 96 corvette rear end for it.
I mean the 52 year old brakes are perfectly capable.......if everybody stops in the same distance I do.

 

Don't get me started on the "cast in" thing...nobody has taken my bounty after about four years and I'm certain it remains safe! lol