Cross Drilled Rotors

[Chiperb]

I have been told and agree that they are of benefit to cool the rotors by allowing friction gasses to escape. Is this really true? Even as it decreases swept braking area? opinions appreciated. cb

[rdorman]

.. cross drilled rotors do the same thing as slotted rotors or slotted pads. The allow the super heated gases and particles to escape. It is refered to as 'wiping the fire band' and it is a good thing.

The reduction in swept area is nominal. The reduction in mass can be significant which is a plus in regards to the energy required to turn or stop the mass. The reduction in mass will also result in higher temperature strickly from a kinetic energy standpoint (ignoring ventilation).

Bottom line, all else being equal they will work better than a non-drilled/slotted rotor with little change in peddle feel. Is it worth the money to upgrade a system that works, no (unless of course you take into account the 'cool' factor!)

Rick

[Back in Black]

You can see what they look like in my photo gallery. Mine are also power (brakes)

[John Hannaford]

A slightly dissenting opinion can be had here:

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

[bmercer]

Wilwood makes similar comments but you gotta love the look of cross drilled/slotted rotors.

http://www.wilwood.com/faq.asp#question7

[a427sc]

Although drilled rotors look race'y, unless you need (and can make use of) the ultimate lightweight rotational package, they are a waste of time. Running street tires? maybe some 17" aftermarket showy wheels or even pin drives, steel hubs, even steel lugnuts and the benefit is lost. The top shelf race teams that use them will replace them after every event, and often during a long endurance run. This is where results overcome any budget considerations. For the average street/track car, they just cost more than they're worth. Expect to see excessive cracking and loss of heat absorbtion/dispersion due the loss of mass in the rotor. Now slots in the pad and rotor will be beneficial, even on a mild street car.

But some people spend cubic $ on other stuff just to look good, so what do I know.

D

[Back in Black]

I suppose a home-done job could be a problem, in addition to likely being unbalanced.
The cross-drilled units are used on most factory motorcycles these days also. No problem. I also remember that one of the original (supposed) reasons for cross-drilling or channeling discs was to channel water so the pads would not hydro-plane.

[DAVID GAGNARD]

I spoke with one of the tech guys at a major brake component company that shall remain nameless for now about drilled and slotted rotors,here is what he told me point blank, drilled and slotted rotors do three things,1. they look cool and sell,2,they make your rotors wear out faster,3,they make your brake pads wear out faster....unless your have a dedicated race car and change rotors and pads after every race you are wasting your money by using drilled and/or slotted rotors....

That's from the horses mouth.....take it for what it's worth....

David

[Aussie Mike]

I did my own on the milling machine. There may be some performance advantages with degassing the pads and clearing away brake dust but it's mostly cosmetic for me.

We always used to drill the discs on our motorcycles to improve their performance in wet weather. On a bike the disc is right out there in the rain and the holes help get the water out from between the pads and the disc. From experience this really made a big difference on the bike. I've noticed that after washing the family car the brakes are a bit ordinary till the water is dispersed. I guess for normal driving the disc is pretty well out of the weather inside the wheel but it might make a difference in very wet conditions.

Cheers

[Excaliber]

,,,,,,well that answered my question, I'm not going with slot or drilled rotors. I've installed the brake cooling duct work and that "helped", but I STILL can't run 10 laps at 100% speed without brake failure.

Short track, lots of twistys. The pedal is still hard and firm (like me) but as the links above stated, there is no "friction" left due to heat.

I'll change the pad material to higher temp unit and try that next.

Most interesting comment I've heard on the track (from a guy driving a Turbo Porsche chasing me):

"I was right on your butt the whole time but couldn't get around you. I was waiting like a buzzard for your brakes to die."

They did! He won! I'm bummed!

Ernie

[DAVID GAGNARD]

Ernie;

Know the feeling,try some Porterfield carbon-kevlar pads,they make them for just about any caliper ever made,but expensive..... Get R-4,designed for racing applications,just put them on for the track and change back to your normal pads for the street....

David

[petek]

Ernie,

Water spray the brakes like they do with those racing big rigs over in Europe! First time I saw 'em on the Speed Channel I laughed my butt off!

Or just mount an N2 bottle somewhere and spray it on the rotors and pads ... should cool 'em down right quick.

You sure your pads aren't dragging on the rotors?

[Excaliber]

Actually I was afraid to say it,,,but I have been seriously thinking about rigging up some kind of water spray device. For now I'm moving up a couple of notches closer to NASCAR spec pads from Wilwood. I'm hopeful I can find something that will be "OK" on the street and give me ten laps at the track.

Ernie

[coyled]

Ernie, what pads and brakes are you running? If the pedal stays hard, you are not getting the brakes hot enough to cook the fluid. I would try the r4 pad from porterfield or you may not have enough brake on the car. Scott

[rdorman]

What pad are you running now Ernie? If you want to try the cooling route the mist needs to be very fine and far upstream. Correct temperature range pad would be better! You mentioned dual use with the wilwoods pads. Any compound aside from the T and Q compounds will put out mounds of dust. Many will have excessive rotor wear on the street, they need to operate at there designed temperature. They will also stop like you just can't beleive. There is such a significant difference in the CF of some of these pads that you will have to get your bias set right for each set.

There is no need to take a stab in the dark on the compound. Lets talk.

Rick

[Roscoe]

Ernie,
Before you start spraying water check out, as suggested, the Porterfield R-4 or R-4S pads. Very good pad.

R-4 Carbon Kevlar
Ten years old and still an outstanding race pad, the original R-4 Carbon Kevlar has proven to be versatile and a superior performing product. We have added two new compounds to compliment the R-4.

R-4 S: Street High-performance & Limited Competition
The high performance street pad of choice. Very high friction level even at cold temperatures.

R-4 E: Endurance Racing Pads with Longer Life
This endurance pad, with special formulation for long races, runs cool and wears longer than our regular R-4. Great for extended time events.

http://www.porterfield-brakes.com/

Roscoe

[Excaliber]

I have the Wilwood "Superlite" four piston calipers on (what I think is) a Granada NON VENTED 11" rotor (or was it 10.5)?

I'm using the Polymatrix "D" compound (with "A" compound being NASCAR specs, the disc rotors "glowing red" and STILL being able to stop).

This pad is "medium" heat range, stops GREAT when cold or moderatly hot, nice pedal feel, very predictable. Changing the calipers and pads made a HUGE difference in being able to more precisly control the brakeing (modulate them).

At an SCCA event the car will be "sitting" for some time and then BAM, your up and it's time to run on COLD brakes! There is no chance to "heat them up". My concern was a higher temp pad would not give me the precise braking modulation I want at lower temps?

At a road course event, running ten laps for instance, I got PLENTY of time to heat them up and HAVE to go with a higher temp pad!

Sounds like I need a couple of different compounds and will have to change out the pads as required.

You think a vented rotor would dissapate enough heat to allow for a "cold" compound in a ten lap race? I can only do 7 laps at full speed as it is now, braking late and hard (which is what I HAVE to do with a Porsche on my butt). It's a one mile track.

The killer is the "hair pin" at the end of the straight, THATS where my brakes die (120 mph down to about 25). I need to do that THREE more laps and I'll be a happy camper!

Ernie

[coyled]

Ernie, run the r4 pads on the 10 lap stuff. They will take a lap too get hot but will work great once hot. Use other pads for the autocross stuff. I run the r4 on mine, works great. I had pad fade with the willwood pads, maybe the wrong compound.Scott

[rdorman]

You have probably read this already but....

http://www.wilwood.org/PolyMatrix%20Catalog.pdf

The D compound starts to loose it at 600 which really isn't all that hot. It you are happy with your balance currently (bias bar centered?) then I would probably go with the J pad for the track. They are good over 1300, have a very, very flat torque curve, will actually stop better than the D pad when cold and the are closest to the CF of the pad you are running now. Even so if you are happy with your front to rear balance the CF of the J pad is still more than 10% higher than the D so you will end up dialing in a little rearward bias. Added plus is your peddle effort will be reduced.

The A, B or C compounds work temperature wise but the torque curves are not as flat, the CF can be significantly higher and they don't work as well cold as the J compound. These are all dusty compounds. And I do mean dusty!

Porterfield make great pads as well (Roscoe sure loves them). I would probably not use the R4-S since it has a lower CF (more peddle effort) and I am not sure of its temp range. The R4 would be good for the big tracks but it optimum range is over 450 so you concern about warm up at the SCCA event may be an issue. The newer R4-1 looks very interesting. I would love to see a temp/CF chart from porterfield. Wish they published one.

NOW GO GET THAT PORSCHE!!!

Rick

[Excaliber]

Thanks for the help guys. These Wilwood pads are dusty little buggars, I hate that part. But am more interested in performance than worrying about brake dust at this point.

.......does make a guy wonder about those R-4's though, I bet they would make less dust.

Ernie