Musche

+1 on Tuboted's advice. I had Zimmerman drilled and only got 1 year of agressive track driving out of them before they started to crack to the edge. Repeated heating to extremes and cooling kill drilled rotors IMHO. I have had slotted ones for two years now with only minimal spider cracks.

blodstrupmoen

Ok , so maybe they wont crack if you don`t use them ..
Ofcourse they last a certain amount of time , but again it is not a question if they will crack or not .. It is when will they crack ?
Zimmermann makes Ok rotors .
oem for the Corvette C5 I don`t know , but that car is not exactly know for its brakes either

I have had drilled zimmermann disc myself ( and EBC ) Both cracked... in the end.
On my Mc on the other hand I have cross drilled rotors . But then again they are solid drilled rotors where the air stream would come from a different angle. And they are better in the wet on an mc than solid .btw , they say that when 3 holes have cracks that comes togheter it is time to change the rotors.

This was the result after a couple of Ring laps ( not mine )



A friend of mine has done some wide testing with his 86 3l 944t .. He even flow testet the brake ducts, both before and after he did changes. For instance Some of the brake colling kits that are available comes with hoses that are not smooth inside , this had a major effect on cooling ..
With his car lowerd and with unmodified cooling ducts ( he has stock brakes and rotors from a 86 ) the brakes would hit 600deg C and his black pagid pads would disintigrate after around 60-70 las on a local track.
After modification of brake cooling ducts he tried with oem pads and they lasted for over 100laps.. Black pagid lasted much longer . He also did some testing later with a IR thermo scan .. But I can`t remeber the numbers.

EBC pads where mentioned , I tried those both green and red a couple of years ago and thought they where crap . I had to drive it like I stole it to get the brakes working , and when they first did work they wore out in no time. I since has tried Ferrodo 3000 and they are good . Now I have put back the stock rotors with black pagids , they are very good on street and would take some track use ..

marky522

If drilled rotors are so much worse then slotted, why does Porsche only offer drilled as an option? I would assume they have done there homework. And the rule of thumb that i have been told is a crack that is extending from any one hole, to another hole, or the outside of the rotor deems it bad.

My .02
Mark

SamGrant951

http://www.mazda6tech.com/index.php?...d=19&Itemid=50

See bottom of page for link to famous Altima brake thread and corner-carvers.com discussion.

Mighty Shilling

For what it's worth, the car will be mostly street with OCCASIONAL (read as once or twice a year) DE duty.

they shouldn't get TOO hot in that normal duty, but I've had my times with track pads that I've gotten HUGE ammounts of fade... particularly at Nelson Ledges for 944fest last year... coming off the back straight after about 7 laps, the pedal became particularly mushy. after a cool-down lap, then parking it in the pits (parking brake off for sure), I got in the car after it cooled, and the pedal was like jello. after pumping the brakes it got better... I am using Ate super blue. is this a problem with my cool-down procedure or do others share similar experiences?

Bri Bro

The porsche rotors are cast, not drilled. Drilling breaks bonds in the metal which allows cracks to form.

marky522

Sorry, said it wrong... It is still being said that drilled (cast) isnt as good as slotted... Just wondering why Porsche would do it this way if it was less stable than slotted or just solid.

Mark

Bri Bro

Don't know, looks?
I am running my first set of rotor with holes as they came with the big reds. I would develope hairline cracks in the solid stock rotor toward the end of the wear limit with the track car but never had any problems with them. I will keep an eye on them but so far, they are holding up nicely and not wearing nearly as fast as stock rotors.

marky522

I higly doubt that Porsche would put something on a 500+HP car that hadnt been COMPLETLY gone over and able to serve its purpose. Ecspecially on there brakes, thats like there pride and joy is there brakes...

Mark

RKD in OKC

My 2001 Boxster S came with drilled rotors. The manual and sales literature said the holes were for water egress in wet braking conditions.

Acetylene

I have Zimmerman cross drilled rotors and Pagid blacks and have had no problems whatsoever. I purchased them for the aesthetics, as, thus far, the car is a street car. I will be participating in DE events this year and we will see how they hold up. I am guessing they will be just fine as a handful of DE events per year is not what most would call "heavy track use".

Fishey

Every Single set of Cross drills I have ever used has cracked from Porsche to Volvo's and from Factory Porsche 993TT Rotors to Cheap drilled they have all failed premature. I actually had 1 zimmerman crack the rotor hat and that was alot of fun to fix...

Ivan Arzola

Gentleman:

first reply on forum. Keep in mind that the more advance cars have a lot more mass to the rotors as they have more diameter than what you are use to. It will take less effort to slow a car with 15" rotors than with 13" also resulting in less heat build up. So when using a x-drilled application, diameter, cooling and vehicle weigth as well as attainable speed is important to take into consideration. I have raced a variety of cars and if given a choice I always would choose solid slotted as big in diameter as possible and the thickest.

One very important factor in the life of any brake rotor is the proper bedding procedure which I can guarantee must users do not know how to perform this correctly. You can trash a new set in one outing on the track. For street use x-drilled would be ok simply because you will not be able to maintain a very high temp on the rotors. Do not forget to choose properly on pad compound.

tommo951

All vented discs can create radial or hairline cracks if they are overheated.
The trick is to get pads to match the discs. I have raced on drilled discs on many different applications and have never noticed more cracks on drilled than non drilled. On thing that can cause cracking is letting pads run too low. This can cause heat transfer and cracking. When racing I never take pads past half wear (endurance racing excluded)

tommo951

You don't fix it you throw it!
Are you saying that the hat crack was caused by cross drilling????