slotted vs cross drilled discs?
02-25-2003, 04:48 PM
#2
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An old thread....
From <A HREF="http://www.netwiz.net/~jds/files/a6_links.html">A6 FAQ</A>...<ul><li><a href="https://forums.audiworld.com/a6/msgs/113441.phtml">https://forums.audiworld.com/a6/msgs/113441.phtml</a</li></ul>
02-25-2003, 05:01 PM
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From the Stoptech website...
"DRILLED VS SLOTTED ROTORS
For many years most racing rotors were drilled. There were two reasons - the holes gave the "fireband" boundary layer of gasses and particulate matter someplace to go and the edges of the holes gave the pad a better "bite".
Unfortunately the drilled holes also reduced the thermal capacity of the discs and served as very effective "stress raisers" significantly decreasing disc life. Improvements in friction materials have pretty much made the drilled rotor a thing of the past in racing. Most racing rotors currently feature a series of tangential slots or channels that serve the same purpose without the attendant disadvantages."
For many years most racing rotors were drilled. There were two reasons - the holes gave the "fireband" boundary layer of gasses and particulate matter someplace to go and the edges of the holes gave the pad a better "bite".
Unfortunately the drilled holes also reduced the thermal capacity of the discs and served as very effective "stress raisers" significantly decreasing disc life. Improvements in friction materials have pretty much made the drilled rotor a thing of the past in racing. Most racing rotors currently feature a series of tangential slots or channels that serve the same purpose without the attendant disadvantages."
02-25-2003, 05:33 PM
#6
I put crossed drilled on my suburban, changed the pads often. After about 30k the brakes started to
shudder. Changed the pads again, bleed the brakes ect. , nothing helped. Upon close inspection the rotors had micro stress cracks between all the holes making the rotors flex and the symtom was shuddering.Changed the rotors to solid and no problems. What does this have to do with Audi brakes? Nothing.
I have stoptechs with 35k on my 4.2, shallow diagonal groves, they work like the day I put them on. I have not wore out a set of pads although i swap back and forth with pagid blue and orange.
I have stoptechs with 35k on my 4.2, shallow diagonal groves, they work like the day I put them on. I have not wore out a set of pads although i swap back and forth with pagid blue and orange.
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02-25-2003, 05:51 PM
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Re: slotted vs cross drilled discs?
I have 85k on my explorers front rotors .They are slotted and cross drilled.Mine came with a large chamfered edge on every hole drilled.Get 35k-40k per set of pads but much better braking.Hope this helps.Only real neg is hard to find a shop that can turn disc.
02-25-2003, 05:57 PM
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An amazing 30 page thread on the issue ...
If you can take the time to sort the wheat from the chaff, you will a lot of good information <A HREF="http://www.altimas.net/forum/showthread.php?threadid=32327">here</a>. Regarding the issue of cracking -- Any abused, poorly designed, or poorly constructed rotor can crack. You do tend to get what you pay for.
<img src="http://www.mouthbreather.net/images/rotors_small.jpg">
<img src="http://audiport.com/959/DSCN0266a.jPG">
<img src="http://64.81.58.216/images/deadparts/crackedpowerslot.jpg">
<img src="http://www.mouthbreather.net/images/rotors_small.jpg">
<img src="http://audiport.com/959/DSCN0266a.jPG">
<img src="http://64.81.58.216/images/deadparts/crackedpowerslot.jpg">
02-25-2003, 07:49 PM
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I would think the best "cross-drilled" rotors are not "drilled" at all....
... but rather fabricated or cast with the holes in place. "Cross-perforated." This yields lower internal stresses.
I don't think I'd bother buying literally drilled rotors. The only point would be to improve short-term cooling, but at the same time you reduce thermal mass and cause stress concentrations, risking cracking. And, for a road car, what's the point? For a race car, the trade-off is better... they are a bit lighter, cool a bit faster, and you toss them in the heap at the end of the day. Cracks, who cares?
Most people like cross-drilled for the same reason as they paint their calipers - vanity.
I would get rotors from a highly reputable firm who has tested the model extensively and which has great reports from other buyers who drive like I do. Slotted or not, cross-perforated or not.
Having said that, my bias is toward slotted or flat, not cross-perforated (unless they have a damned good justification for it).
I don't think I'd bother buying literally drilled rotors. The only point would be to improve short-term cooling, but at the same time you reduce thermal mass and cause stress concentrations, risking cracking. And, for a road car, what's the point? For a race car, the trade-off is better... they are a bit lighter, cool a bit faster, and you toss them in the heap at the end of the day. Cracks, who cares?
Most people like cross-drilled for the same reason as they paint their calipers - vanity.
I would get rotors from a highly reputable firm who has tested the model extensively and which has great reports from other buyers who drive like I do. Slotted or not, cross-perforated or not.
Having said that, my bias is toward slotted or flat, not cross-perforated (unless they have a damned good justification for it).