Quattro Brain Trust: Tell me why this is a bad idea....
02-08-2008, 05:23 PM
#1
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Quattro Brain Trust: Tell me why this is a bad idea....
My brakes have started shimmying, I'm pretty sure it is from uneven pad material deposits on the rotors.
I'm going to hit the rotors with some garnet paper, I would like to keep the rotors on the car if possible. Of course the rotors are hard to sand while they are on the car. Sanding the rotors would me much easier if I could get them to rotate...
Would it be a bad idea to put the front end on jack stands, fully set the e-brake, block the rear wheels and then let the car idle in drive???
Would the front rotors move in this setup?
Would this damage the quattro?
I'm going to hit the rotors with some garnet paper, I would like to keep the rotors on the car if possible. Of course the rotors are hard to sand while they are on the car. Sanding the rotors would me much easier if I could get them to rotate...
Would it be a bad idea to put the front end on jack stands, fully set the e-brake, block the rear wheels and then let the car idle in drive???
Would the front rotors move in this setup?
Would this damage the quattro?
02-08-2008, 05:39 PM
#2
sounds excessively hazardous to me - and the roadgoing method is more fun, anyway.
Find a long, empty road where you can perform a half-dozen hard brakings from [as fast as you can reasonably go] down to 5-10 mph. The important thing is to not come to a complete stop at the end of the hard decel. This process heats the rotors up enough to scrub off the deposits, and nobody risks getting run over in the garage.
02-08-2008, 05:51 PM
#3
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Whoa, we need to find some harmless puzzles to challenge Cole's brain - this is
suicidal sounding to me even if very creative and a bit complex for the task. But, if you do it please set up a video camera for our later enjoyment!
02-08-2008, 05:54 PM
#4
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I tried that, I didn't work and then I read why it was a bad idea...
<a href="http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml">The following is from this very informative page</a>
____________________________________________
Cast iron is an alloy of iron and silicon in solution interspersed with particles of carbon. At elevated temperatures, inclusions of carbides begin to form in the matrix. In the case of the brake disk, any uneven deposits - standing proud of the disc surface - become hotter than the surrounding metal. Every time that the leading edge of one of the deposits rotates into contact with the pad, the local temperature increases. When this local temperature reaches around 1200 or 1300 degrees F. the cast iron under the deposit begins to transform into cementite (an iron carbide in which three atoms of iron combine with one atom of carbon). Cementite is very hard, very abrasive and is a poor heat sink. If severe use continues the system will enter a self-defeating spiral - the amount and depth of the cementite increases with increasing temperature and so does the brake roughness. Drat!
____________________________________________
Cast iron is an alloy of iron and silicon in solution interspersed with particles of carbon. At elevated temperatures, inclusions of carbides begin to form in the matrix. In the case of the brake disk, any uneven deposits - standing proud of the disc surface - become hotter than the surrounding metal. Every time that the leading edge of one of the deposits rotates into contact with the pad, the local temperature increases. When this local temperature reaches around 1200 or 1300 degrees F. the cast iron under the deposit begins to transform into cementite (an iron carbide in which three atoms of iron combine with one atom of carbon). Cementite is very hard, very abrasive and is a poor heat sink. If severe use continues the system will enter a self-defeating spiral - the amount and depth of the cementite increases with increasing temperature and so does the brake roughness. Drat!
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02-08-2008, 06:06 PM
#8
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that has been my experience. but on the stoptech tech page below it list sanding as a possible cure?
They just started shimying, so I thought sanding may be worth a shot. I will probably just take them in and have them turned...
02-08-2008, 08:05 PM
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Good thinking, but someone beat you to it. A bit more complex.
Take a look at the video in particular. A bit long winded, but interesting. Not quite sure how Audi's Torsen differential would respond to one wheel being turned. I gather the front or rear differential being "electronically locking" in Audi-speak (open diff in regular speak) would allow the rotor being machined to turn without turning the center diff.
Hunter does list drive flanges for the A6, so it apparently can be done. Been a long time since I ran a rotor lathe, the early on-vehicle lathes were much more primitive, but worked great on the then-new front wheel drive imports.
That being said, this system might be worth looking into for your problem. Others might be able to comment on issues with Audi.<ul><li><a href="http://www.hunter.com/pub/product/lathe/5071T/index.htm">http://www.hunter.com/pub/product/lathe/5071T/index.htm</a</li></ul>
Hunter does list drive flanges for the A6, so it apparently can be done. Been a long time since I ran a rotor lathe, the early on-vehicle lathes were much more primitive, but worked great on the then-new front wheel drive imports.
That being said, this system might be worth looking into for your problem. Others might be able to comment on issues with Audi.<ul><li><a href="http://www.hunter.com/pub/product/lathe/5071T/index.htm">http://www.hunter.com/pub/product/lathe/5071T/index.htm</a</li></ul>
02-09-2008, 05:05 AM
#10
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Great idea!! Let me get the video camera ready first! You must be joking...
Jack the car up, put it in drive without wheels on seems like a good way to smash up the car and what's around it. It could also be the ultimate dangerous power tool.