Warped Rotors
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Let's put it this way. If you have the space on approach you slow down gradually and by the time you come up to whatever limit line your body shouldn't be thrown up against the windshield or restrained by the seat belts..
Not saying anyone should normally drive like an old lady.. just saying there is a smooth way to do it and a not so smooth way. And the not so smooth way generates more stresses.. Think of it this way as a physics problem.. If I have a 5000Kg vehicle moving at 50m/s that is a kinetic energy of 1/2 * 5000 * 50 * 50 = 1/2 mv(sq).. = 6.25 M Joules. That's the amount of energy that needs to be dissipated through the brakes to bring the car to rest. If you do it over 500m vs say 100m then you are absorbing that energy in a much shorter period of time with much less airflow to cool/transfer that energy from the brakes. Thus the rotor / pads are heated to much higher temperatures. Bigger brakes have more mass to them and they can absorb a lot more energy, but there are limits. Now take that same scenario and ride the brakes down a hill on the way to stop at that light.. so even at 50m/s there is a slight braking due the brakes dragging so they are already absorbing energy.. Then stop hard in 100m (or whatever).. Now the temperature is even higher and more prone to glazing of the pads or warpage. . Not saying a good brake system like a Porsche can't handle it.. Personally I think you can abuse the hell out of them and there isn't much of a problem. The bigger issue is overheating them by gently riding them.. But repeat that same sequence dozens of time daily and over a period of time you are getting a lot of temperature cycles and things happen that aren't good. Never thought of it much this way, until I was involved with some jet aircraft brakes and looked at just how much abuse they took slowing a heavy object in a short period of time.. sometimes they literally melt.. Also note that PCCB yellow brakes are notorious as I have learned at overheating, especially with track use. They are so good that they don't fade, right up to the time that they start breaking down and you never realize it is happening... So overheating brakes ain't as hard as one might think at times..
Not saying anyone should normally drive like an old lady.. just saying there is a smooth way to do it and a not so smooth way. And the not so smooth way generates more stresses.. Think of it this way as a physics problem.. If I have a 5000Kg vehicle moving at 50m/s that is a kinetic energy of 1/2 * 5000 * 50 * 50 = 1/2 mv(sq).. = 6.25 M Joules. That's the amount of energy that needs to be dissipated through the brakes to bring the car to rest. If you do it over 500m vs say 100m then you are absorbing that energy in a much shorter period of time with much less airflow to cool/transfer that energy from the brakes. Thus the rotor / pads are heated to much higher temperatures. Bigger brakes have more mass to them and they can absorb a lot more energy, but there are limits. Now take that same scenario and ride the brakes down a hill on the way to stop at that light.. so even at 50m/s there is a slight braking due the brakes dragging so they are already absorbing energy.. Then stop hard in 100m (or whatever).. Now the temperature is even higher and more prone to glazing of the pads or warpage. . Not saying a good brake system like a Porsche can't handle it.. Personally I think you can abuse the hell out of them and there isn't much of a problem. The bigger issue is overheating them by gently riding them.. But repeat that same sequence dozens of time daily and over a period of time you are getting a lot of temperature cycles and things happen that aren't good. Never thought of it much this way, until I was involved with some jet aircraft brakes and looked at just how much abuse they took slowing a heavy object in a short period of time.. sometimes they literally melt.. Also note that PCCB yellow brakes are notorious as I have learned at overheating, especially with track use. They are so good that they don't fade, right up to the time that they start breaking down and you never realize it is happening... So overheating brakes ain't as hard as one might think at times..
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Nobody thinks they have bad habits.. I have no clue as to the op driving habits just explaining scenarios I've seen..
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Not trying to insult your manhood. But you are the one with the unique problem and blowing out rotors in groups. And the info you supplied was rather thin..
Is it a PDK or not..? If it is PDK then you have an electronic PTV system. if you have an M7 do you have PTV? if so, then it is a mechanical PTV system..
If you just want to hear that it is a mechanical fault.. Then Ok, probably a mechanical fault, although generally that isn't the case. What I do agree is odd is that it apparently happened in a short span of miles.. and maybe something is dragging in the system related to PTV or some kind of ABS problem but I've never seen an ABS system failure cause brakes to drag..
Something is causing heat at your rotors, because they don't warp otherwise. The question is why?
Is it a PDK or not..? If it is PDK then you have an electronic PTV system. if you have an M7 do you have PTV? if so, then it is a mechanical PTV system..
If you just want to hear that it is a mechanical fault.. Then Ok, probably a mechanical fault, although generally that isn't the case. What I do agree is odd is that it apparently happened in a short span of miles.. and maybe something is dragging in the system related to PTV or some kind of ABS problem but I've never seen an ABS system failure cause brakes to drag..
Something is causing heat at your rotors, because they don't warp otherwise. The question is why?
Last edited by scatkins; May 9, 2014 at 10:19 AM.
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This was of the A380 testing, I had some involvement in the B777 testing back in the early 90's and there are a lot of videos of the test to failure certification on a runway where they literally melted the brakes into a flaming pile of goo. And what was most surprising is how easy it was to overheat the brakes by just applying them and continuing thrusting the aircraft down the runway. Over just a few thousand feed they flamed.
The physics of just how much energy must be dissipated by brakes, even on an auto is something we tend to take for granted.
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If you want to rule out driving habits and component failure, then Rotor Contamination is the only thing left, that I can think of.
Is there some chemical getting sprayed on the rotors that interferes with the even transfer of pad material to the rotor, that in turn causes uneven deposits, giving the symptoms of warped rotors.
Uneven Deposits are difficult to correct, short of replacing the rotor.
Just another theory
Is there some chemical getting sprayed on the rotors that interferes with the even transfer of pad material to the rotor, that in turn causes uneven deposits, giving the symptoms of warped rotors.
Uneven Deposits are difficult to correct, short of replacing the rotor.
Just another theory
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Soon after I started using it my brakes developed a squeal when I stopped. Eventually I stopped using Sonax and about a month later the squeal went away. I'm not saying the two were connected, but I was always suspicious it was somehow the cause.
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In 40+ years of driving Porsches, the only set of rotors I ever warped was in the early 80's on my 930 Turbo, when I was a young rookie track driver who didn't know any better. I came off the track at Lime Rock after a spirited 20 minute session and just rolled directly into the paddock, shut off the car and pulled up the handbrake hard.
Ninety minutes later I went back out on the track and the rotors were warped so bad that the pulsing on the brake pedal and wheels almost shook the steering wheel right out of my hands.
Expensive learning experience to not set the Emergency Brake when the rotors are hot.
Ninety minutes later I went back out on the track and the rotors were warped so bad that the pulsing on the brake pedal and wheels almost shook the steering wheel right out of my hands.
Expensive learning experience to not set the Emergency Brake when the rotors are hot.
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If you want to rule out driving habits and component failure, then Rotor Contamination is the only thing left, that I can think of. Is there some chemical getting sprayed on the rotors that interferes with the even transfer of pad material to the rotor, that in turn causes uneven deposits, giving the symptoms of warped rotors. Uneven Deposits are difficult to correct, short of replacing the rotor. Just another theory
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