xdrill rotr
06-10-2001, 11:07 AM
#1
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Thread Starter
xdrill rotr
Any comments on the cross drilled rotors that are offered for $70 on this BB.
Can u use drilled on front and not back or back and not front. Hate to pass up a good deal, just paid 125 for my last set of fronts installed by the shop.
Can u use drilled on front and not back or back and not front. Hate to pass up a good deal, just paid 125 for my last set of fronts installed by the shop.
06-10-2001, 01:48 PM
#2
Technical Specialist
Rennlist
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Rennlist
Lifetime Member
Mrdi,
I can't vouch for the particular drilled rotors the vendor is selling, but I can tell you a little about them in general.
So called "drilled" rotors make the rotor lighter and give water a place to go during braking. There's two basic types of drilled rotors, those that have cast-in holes during the manufacturing process, and those that are indeed drilled. Sometimes the rotors with drilled holes also have the holes chamfered (Porsche found that chamfered holes help to keep brake dust buildup from clogging the holes). Porsche "drilled" rotors are the cast-in variety. They aren't drilled to make the holes, and thus aren't as subject to the big problem with drilled rotors, which is cracks between the holes (Porsche rotors with the cast-in holes aren't immune to cracks, but they'll go longer before the problem surfaces). If you get real drilled rotors, you need to keep an eye on their condition - they are not put on and forget. Once a crack starts, start looking for a new rotor. For drivers education, if there's a 1/2 inch crack, they'll likely fail tech inspection.
Aside from the solid rotors, there are also slotted rotors, where 3 or more slots are put onto each side to wipe dust and water away from the brake pads. This is less intrusive than drilling, and as such doesn't have as much an effect on the structure of the rotor. ATE has a rotor called a PowerDisk which has a swirling slotted pattern on it which is put on the rotor during the manufacturing process. I really like those, and used them on my 911SC brakes with Pagid Orange pads, and never had any brake pad material depositing problems, which others have mentioned. I think I paid less than $60 each for the ATE PowerDisk's from Paragon Products in TX.
FWIW, on my 930 brakes, I have slotted rotors on the front and cryo-treated Porsche (with cast-in holes) rotors in the rear.
[ 10-06-2001: Message edited by: Bill Gregory ]
I can't vouch for the particular drilled rotors the vendor is selling, but I can tell you a little about them in general.
So called "drilled" rotors make the rotor lighter and give water a place to go during braking. There's two basic types of drilled rotors, those that have cast-in holes during the manufacturing process, and those that are indeed drilled. Sometimes the rotors with drilled holes also have the holes chamfered (Porsche found that chamfered holes help to keep brake dust buildup from clogging the holes). Porsche "drilled" rotors are the cast-in variety. They aren't drilled to make the holes, and thus aren't as subject to the big problem with drilled rotors, which is cracks between the holes (Porsche rotors with the cast-in holes aren't immune to cracks, but they'll go longer before the problem surfaces). If you get real drilled rotors, you need to keep an eye on their condition - they are not put on and forget. Once a crack starts, start looking for a new rotor. For drivers education, if there's a 1/2 inch crack, they'll likely fail tech inspection.
Aside from the solid rotors, there are also slotted rotors, where 3 or more slots are put onto each side to wipe dust and water away from the brake pads. This is less intrusive than drilling, and as such doesn't have as much an effect on the structure of the rotor. ATE has a rotor called a PowerDisk which has a swirling slotted pattern on it which is put on the rotor during the manufacturing process. I really like those, and used them on my 911SC brakes with Pagid Orange pads, and never had any brake pad material depositing problems, which others have mentioned. I think I paid less than $60 each for the ATE PowerDisk's from Paragon Products in TX.
FWIW, on my 930 brakes, I have slotted rotors on the front and cryo-treated Porsche (with cast-in holes) rotors in the rear.
[ 10-06-2001: Message edited by: Bill Gregory ]
06-11-2001, 04:56 AM
#3
Race Car
Mrdi! Good to find an old friend on a "new" board. 
In regards to cross-drilled rotors...I have A LOT to say. For starters, I have been using them for about four years, ever since my second track event.
Stay w/the German rotors like Zimmerman or Sebro due to the fact that they cast in the holes at production time.
The companies that drill the holes later only magnify a problem inherent to ALL rotors at birth...stress relieving! This, of course can be alleviated by cryogenically treating the rotors...another interesting controversy.
I have used cross-drilled rotors that were drilled after production, rotors that were cast during production and rotors that were cast during production and cryogenically treated afterwards, oh and rotors that were drilled after production and cryogenically treated. They all have different characteristics...the main one being...DON'T USE ROTORS THAT WERE DRILLED AFTER PRODUCTION!! They will crack after one use.
Now, to answer your first question...yes, they can be mixed, I would suggest cross-drilled on the front first, you can upgrade the rear later. I probably wouldn't suggest getting cross-drilled in the rear first and regular on the front due to the fact that CD rotors provide a better "bite" under heavy braking...a 964, which I believe you own, really needs no help in the rear as it is fairly misbalanced by the factory in the first place...reference the "tubbs" family website and the trials he has gone through changing out brake biasing valves.
In closing, if you are participating in track events, regardless of what rotor configuration you use...they all crack! Rotors are pretty much accepted as a consumable in my household - no, I don't eat them! Well, sort of, anyway...I change out a set of fronts about every 5 to 7 events, depending on what configuration I used and what tracks I've been to.
I would suggest that anybody participating in track events either get a CD -or- slotted rotor setup, the benefits are worth it...the cryogenic idea is up to you.
[ 11-06-2001: Message edited by: Jeff Curtis ]
In regards to cross-drilled rotors...I have A LOT to say. For starters, I have been using them for about four years, ever since my second track event.
Stay w/the German rotors like Zimmerman or Sebro due to the fact that they cast in the holes at production time.
The companies that drill the holes later only magnify a problem inherent to ALL rotors at birth...stress relieving! This, of course can be alleviated by cryogenically treating the rotors...another interesting controversy.
I have used cross-drilled rotors that were drilled after production, rotors that were cast during production and rotors that were cast during production and cryogenically treated afterwards, oh and rotors that were drilled after production and cryogenically treated. They all have different characteristics...the main one being...DON'T USE ROTORS THAT WERE DRILLED AFTER PRODUCTION!! They will crack after one use.
Now, to answer your first question...yes, they can be mixed, I would suggest cross-drilled on the front first, you can upgrade the rear later. I probably wouldn't suggest getting cross-drilled in the rear first and regular on the front due to the fact that CD rotors provide a better "bite" under heavy braking...a 964, which I believe you own, really needs no help in the rear as it is fairly misbalanced by the factory in the first place...reference the "tubbs" family website and the trials he has gone through changing out brake biasing valves.
In closing, if you are participating in track events, regardless of what rotor configuration you use...they all crack! Rotors are pretty much accepted as a consumable in my household - no, I don't eat them! Well, sort of, anyway...I change out a set of fronts about every 5 to 7 events, depending on what configuration I used and what tracks I've been to.
I would suggest that anybody participating in track events either get a CD -or- slotted rotor setup, the benefits are worth it...the cryogenic idea is up to you.
[ 11-06-2001: Message edited by: Jeff Curtis ]
