Cross Drilled rotors - clogged holes?

[aj88cab]

Before my last DE I was bleeding the brakes and found this on my left-front rotor. The holes were clogged (see pic). It was easy to just stick a wire in them and clean them out, but I was wondering if anybody has had this problem, and what might be the cause.

And now for the confession...I had left the Hawk Blue pads on the car for 2 months since my last DE and did about 1k miles of street driving with them. I'm guessing that is not a good thing to do.

Thanks
Andrew

[Plavan]

I have never had any holes clog on our rotors. Maybe its time to change to a different brake pad. We all use Ferodo pads in our race cars. They are cheap and offer very good feel and braking. They are also easy on the rotors.
Some guys swear to use Pagid $$$$. We all think they are a waste of money and kill your rotors. If I can lock up my brakes at the begining of a race and at the end of the race, my pads are working

[dmarv]

Crossed drilled rotors, when done correctly, have a chamfer of about of 45 degrees. When the rotor wears, it can loose this chamfer and the holes are now at 90 degrees. The holes then act as a cutting edge and will remove material from the pad, sometimes clogging the holes. Were both rotors clogged, or just the one? By the picture, your rotors look fairly new. Did you buy them drilled, or have them drilled after purchase?

[Emission]

My rotors collect a tiny bit of dust/pad material in the holes, but nothing near what you are experiencing! I'd try different pads as something isn't adding up.

Here is a pic of my rotor "dirty" (without me punching the crud out of the drilled holes).

[aj88cab]

Originally posted by dmarv
Were both rotors clogged, or just the one? By the picture, your rotors look fairly new. Did you buy them drilled, or have them drilled after purchase?

I installed the rotors new in May. I rebuilt all the calipers at that time also. The rotors were purchased cross drilled. They have 3 DE's, 2 "spirited" mountain runs, and about 2k miles of street driving (1k with the Hawk Blues) on them. Only this left-front rotor had the problem. I didn't notice any additional clogging after the DE last month. I have the street pads (OEM) installed now and am keeping an eye on it.

The fact that it only happened on one side concerns me. There is no pulling, the car stops straight as an arrow.

Thanks
Andrew

[Emission]

Do you think it could be the rotation?

In my pic, the rotor turns clockwise. In your pic, it appears the rotor turns counterclockwise - this is the opposite of how Porsche "directionalizes" their drilled rotors. Are both of your rotors identical (so one turns one direction, the other the opposite)? Mine are different, therefore they have specific sides.

[ewave]

My rotors were very clogged on both a 930 and a 911 with turbo style rotors- Front AND rear. Very hard driving, - Used a set of pads in one wheekend. I just used a 1/8 inch punch to clean them out...

[dmarv]

Sounds like a friction material issue to me. I would do what you said and keep an eye on the OE pads.

[aj88cab]

Originally posted by Emission
Do you think it could be the rotation?

In my pic, the rotor turns clockwise. In your pic, it appears the rotor turns counterclockwise - this is the opposite of how Porsche "directionalizes" their drilled rotors. Are both of your rotors identical (so one turns one direction, the other the opposite)? Mine are different, therefore they have specific sides.

Interesting point. These are Zimmerman rotors and the "direction" of the holes is the same. They do not make a left and right side rotor as far as I know. So, yes, the holes "turn" in different directions. I noticed this when I purchaced them and found a post about it here as well. There didn't seem to be any concern expressed in the postings. But.....

[Emission]

Originally posted by aj88cab
I noticed this when I purchaced them and found a post about it here as well. There didn't seem to be any concern expressed in the postings. But.....

I can't understand how it would make ANY difference, but since you are getting buildup on only that side...

[aj88cab]

Originally posted by Emission
I can't understand how it would make ANY difference, but since you are getting buildup on only that side...

I wouldn't think so either, but it is the only obvious difference from side to side. I'll kep an eye on things and see what happens.

Anybody have any specific experience with Hawk pads and rotor wear?

Thanks for all the input guys.

Andrew

[Grady Clay]

Is there anything restricting the air flow thru the internal rotor vents? Inspect the openings toward the spindle.

Everyone, note the shadow of the pad on the rotor surface.

Best,
Grady

[aj88cab]

I will check for clear air flow, but I'm pretty sure there was no obstruction at the internal vents. Good idea though!

The shadow on the rotor was there after I cleaned the assembly with break cleaner before working on it. What you see is the residue from where the pad was contacting the rotor. It's just dried brake dust and it wiped clean.

Andrew

[carrue529]

my 2c,

I'm using the Zimmerman rotors, and had the clogging issue after one DE event while using Mintex brake pads, switched to Hawk no clogging after 4 DE events

[Bill Verburg]

They can clog but most people clean w/ water or air often enough that its not an issue.

The pictured 911 rotors have an internal structure which doesn't move as much air at speed as the 930 rotors which are factory drilled(Actually cast but das macht nichts)

Some pads do generate far more dust and detrius than others

[aj88cab]

Originally posted by Bill Verburg
They can clog but most people clean w/ water or air often enough that its not an issue.

Bill, are you saying I need to bathe more often?

Andrew

[dvkk]

Originally posted by dmarv
Crossed drilled rotors, when done correctly, have a chamfer of about of 45 degrees. When the rotor wears, it can loose this chamfer and the holes are now at 90 degrees. The holes then act as a cutting edge and will remove material from the pad,

An interesting theory I used to believe. After inspecting the rotors on my friend's collection of motorcycles, it doesn't seem to concern the manufacturers. Honda, Yamaha and Suzuki all have absolutely no chamfer on any holes, just a sharp edge.

[Chris Lovell]

Originally Posted by Bill Verburg

They can clog but most people clean w/ water or air often enough that its not an issue.

The pictured 911 rotors have an internal structure which doesn't move as much air at speed as the 930 rotors which are factory drilled(Actually cast but das macht nichts)

Some pads do generate far more dust and detrius than others

Bill,
"clean with w/ water or air"? Maybe I am just dated (that's an understatement) but aren't we supposed to keep shop air away from brakes as a safety practice? If asbestos and other problems are history, I would like to use air to clear these clogs and help with other brake work.
Thanks for any clarification.

[aj88cab]

Always a surprize to see an old thread pop up again....

Update - I do not use cross-drilled rotors anymore. The front rotors developed cracks, I replaced them, then the rears started to crack. I switched to Powerslot rotors back in April. I still use the Hawk Blue pads. The x-drilled rotors with new pads were great for the first DE then they would develop "saturn rings" that would wear the pads into a "wavey" surface, with clogged holes, and heavy rotor wear that resulted in a ridge on the edge of the rotor. The braking would degrade after a DE or two, and end up fading pretty bad, and the cracking is inevitable. I was getting about 2 DEs out of the front pads and about 3 on the rears. Some of the pads would wear at an angle. All this after I installed some cooling ducts too.

The Powerslot rotors and Hawk Blue pads currently installed have run 4 DE's, the braking is still as good as day one, the pads are wearing evenly front to back, no angled pad wear, nothing to clog, and very little rotor wear with no rings or ridges after the 4 DEs. I still run the factory calipers, on a typically overweight Carrera Cab. The pads are about done, but I could get another day out of them if I needed, but they will go in the "spares" box...safety first!

I have a set of slightly used (one DE) front x-drilled rotors I will make anyone a good deal on

My previous rotor woes:

Are my X-Drilled rotors toast (small cracks)?

Odd place for a rotor crack
Andrew

[KTL]

Might want to consider a different pad, even though your problems have been solved with the PowerSlot rotors and Hawk Blue combination.

Hawk Blues are known for being harsh on rotors. For the same price you could use PF97 Performance Friction pads and experience not nearly the rotor wear, with exceptional braking performance- very fade resistant.

I'd stick with the stock undrilled Zimmermans in lieu of the PowerSlots. I believe I recall the Porsche PowerSlots are slotted OEM rotors. So there's nothing a whole lot better about them other than the nice plating and slots- maybe some additional balancing. The OEM Zimmerman rotors are certainly up to the task of track use.