Warped rotors after warranty.....
03-05-2002, 01:26 PM
#13
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experts (which isn't me) say: slot but don't drill, if you want holes get ones that are cast in...
drilling afterwards supposedly results in opportunities for through-cracking at high temps. some tracks/clubs ban after-the-fact drilled rotors for this reason. high end rotors have holes are cast-in: Porsche for example.
both theoretically clean pads and provide opportunity for 'out-gassing' and improved wet performance, but I think most are sold these days as appearance horsepower. both will wear your pads faster, although that's immaterial if you drive the car hard - you'll rip through pads anyway. fun tax.
both theoretically clean pads and provide opportunity for 'out-gassing' and improved wet performance, but I think most are sold these days as appearance horsepower. both will wear your pads faster, although that's immaterial if you drive the car hard - you'll rip through pads anyway. fun tax.
03-05-2002, 02:04 PM
#14
Cross drilling is the method of choice for superior all weather braking and maximal rotor cooling
for roadcars by the carmakers of the fastest vehicles in the world. Don't believe me, just look under a Porsche, Lambo, or Ferrari fender. 
03-05-2002, 03:48 PM
#15
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IMO, that's probably out-of-date and bad advice for most people...(long)
first, i'll bet ALL the mfr's you mention have cast or otherwise specially mfr'd holes. i know Porsche does. that's not the same as drilling plain-jane rotors, which is what most cheap options available to the laymen are. maybe cryo-treating the rotor helps with this problem, that does sound plausible to me.
but second, the best information seems to be that drilled rotors are simply not best practice. under heavy use they develop cracks and potential to fail. and slotting is just as effective without the major structural and thermal downsides of drilled holes.
i do realize everyone has to have cool drilled rotors to show off with their imitation big-red kits, and hey, if that's someone's priority, fine. (did i tell you about the sweet rear wing and gold badges i'm putting on next week? good for at least 50hp.). there's no doubt that's a major factor in why most of the aftermarket stuff is drilled.
even guys selling the stuff who have every motivation to tell people that drilling is great are saying this now:
http://www.stoptech.com/whitepapers/brake_systems_and_upgrade_selections_122701.htm
http://www.baer.com/faq.shtm
http://tech.rennlist.com/911/911scfaqbrakes.PDF
honestly, the biggest benefit for a street car is going to come from a set of excellent aftermarket STREET pads anyway like Hawk/Kerr/Mintex/Pagids or the like. after that get a nice fat set of streetable front calipers and slotted rotors if you must, like the BIRA gear: http://www.qrsmotorsport.com/a6_brakes.htm.
then again, that's just my opinion...
but second, the best information seems to be that drilled rotors are simply not best practice. under heavy use they develop cracks and potential to fail. and slotting is just as effective without the major structural and thermal downsides of drilled holes.
i do realize everyone has to have cool drilled rotors to show off with their imitation big-red kits, and hey, if that's someone's priority, fine. (did i tell you about the sweet rear wing and gold badges i'm putting on next week? good for at least 50hp.). there's no doubt that's a major factor in why most of the aftermarket stuff is drilled.
even guys selling the stuff who have every motivation to tell people that drilling is great are saying this now:
http://www.stoptech.com/whitepapers/brake_systems_and_upgrade_selections_122701.htm
http://www.baer.com/faq.shtm
http://tech.rennlist.com/911/911scfaqbrakes.PDF
honestly, the biggest benefit for a street car is going to come from a set of excellent aftermarket STREET pads anyway like Hawk/Kerr/Mintex/Pagids or the like. after that get a nice fat set of streetable front calipers and slotted rotors if you must, like the BIRA gear: http://www.qrsmotorsport.com/a6_brakes.htm.
then again, that's just my opinion...
03-05-2002, 04:49 PM
#16
Actually, Porsche does not cast their rotors with holes; they drill them like everyone else. Slots
crack also. I have pics to prove it. rotors and pads are a throw away item on the track. For a roadcar, the holes are strictly to let rain water that turns to steam on contact to not lie between pad and rotor to effect braking quality and to assist in rotor cooling. Slots are good for better initial bite on the pad which is why they are used in racing. Pads get tossed. The early problems with excessive cracking with cross drills was because they drilled non-camphered 5mm holes. Now they are 2-3mm and camphered with a design to not interfere with the structural rigidity problems caused by the design of the vented rotor. How do I know that Porsche doesn't cast in their holes? Larry TT corrected me when a Quattro club guy asked the brake guy at the Porsche factory whether they cast drilled or mechanically drilled. Since, I had my friend in Germany (very close to Weissach) ask the same question. Porsche drills like everyone else, but they use a special heat treating process to solidify the metallury of each rotor. Hence, I had to apologize to Larry TT, which was very difficult. I guess it is who you choose to listen to.
03-05-2002, 05:00 PM
#17
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Stoptech white papers, very useful!
They do support slotting over drilling (esp if aftermarket machining).
More importantly, they indicate that warping may not be as common as we thought... it may be deposition of pad material into the disk. The metalurgical process is rather complicated, but in any case, one would hope that Audi could engineer a good combination of pad, rotor, and fluid that can handle aggressive driving.
Here are the links:
<A HREF="http://stoptech.com/whitepapers/brake_systems_and_upgrade_selections_122701.htm">S topTech - Brake Systems & Upgrade Considerations</A>
<A HREF="http://stoptech.com/whitepapers/warped_rotors_myth.htm">Stoptech - The Warped Brake Disc and Other Myths</A>
<A HREF="http://stoptech.com/technical/">Stoptech -- Tech articles</A>
More importantly, they indicate that warping may not be as common as we thought... it may be deposition of pad material into the disk. The metalurgical process is rather complicated, but in any case, one would hope that Audi could engineer a good combination of pad, rotor, and fluid that can handle aggressive driving.
Here are the links:
<A HREF="http://stoptech.com/whitepapers/brake_systems_and_upgrade_selections_122701.htm">S topTech - Brake Systems & Upgrade Considerations</A>
<A HREF="http://stoptech.com/whitepapers/warped_rotors_myth.htm">Stoptech - The Warped Brake Disc and Other Myths</A>
<A HREF="http://stoptech.com/technical/">Stoptech -- Tech articles</A>