warped brake disc and other myths of the brakes

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"In fact every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures."

That may be true for the author but I have had several cases in our shop of new rotors being warped from mishandling or improper storage. But regardless of the cause rotors with too much runout need to be corrected or replaced.
 
The guy that wrote that baloney has never turned a disc on a brake lathe! I have and I have seen the metal, not pad material being removed from the disc.

I see stuff like that read often and wonder who started that rumor? Sure sometimes pad material on the rotor does ocasionally happen but 99% of the rotors I have turned were warped or had thickness variation in the metal and not pad material stuck to the rotor.
 
Originally Posted By: Chris142
The guy that wrote that baloney has never turned a disc on a brake lathe! I have and I have seen the metal, not pad material being removed from the disc.

I see stuff like that read often and wonder who started that rumor? Sure sometimes pad material on the rotor does ocasionally happen but 99% of the rotors I have turned were warped or had thickness variation in the metal and not pad material stuck to the rotor.

My 35 years in the field agrees with you. Can you imagine how many brake jobs I must have done working for a school fleet.I don't remember any instance of pad material causing runout.
 
Originally Posted By: Chris142
The guy that wrote that baloney has never turned a disc on a brake lathe! I have and I have seen the metal, not pad material being removed from the disc.

I see stuff like that read often and wonder who started that rumor? Sure sometimes pad material on the rotor does ocasionally happen but 99% of the rotors I have turned were warped or had thickness variation in the metal and not pad material stuck to the rotor.


It's not baloney but whatever.. I have personally seen on my own cars pad material marks like are shown in the images. Also I have never seen a warped rotor and I have turned some on the lathe personally myself. Change in thickness yes, 100%. Warping, 100% no.
 
I've seen all of this. Turning the rotor to true it up. Metal being cut from it. A very few instances of pad material on the rotor.
Recently I changed the front rotors on my Taurus. No sign of any pad material. They were just chewed up. Metal worn away from 160,000 miles of braking.
 
Another example of someone with far too much regard for their own experience writing an editorial piece.

Pack up and go home guys, we've figured it out. Brake discs cannot and do not warp, it's been some esoteric anomaly causing the problems all along. We just needed some trusted expert to let us all know. Now go out there and buy the cheapest chiense rotors you can find, they're just as good as the top line stuff, just get quality pads.....
 
Go ahead and stick your head in the dirt. Meantime, the few of us who can learn are saving tons of dough by realizing the difference between PAD issues and ROTOR issues.

You still get to do whatever you think is best...
 
Originally Posted By: bradepb
Originally Posted By: Chris142
The guy that wrote that baloney has never turned a disc on a brake lathe! I have and I have seen the metal, not pad material being removed from the disc.

I see stuff like that read often and wonder who started that rumor? Sure sometimes pad material on the rotor does ocasionally happen but 99% of the rotors I have turned were warped or had thickness variation in the metal and not pad material stuck to the rotor.

My 35 years in the field agrees with you. Can you imagine how many brake jobs I must have done working for a school fleet.I don't remember any instance of pad material causing runout.
You can always set a lathe to cut deep enough to remove metal, THAT doesn't prove anything.
 
Originally Posted By: HerrStig
Originally Posted By: bradepb
Originally Posted By: Chris142
The guy that wrote that baloney has never turned a disc on a brake lathe! I have and I have seen the metal, not pad material being removed from the disc.

I see stuff like that read often and wonder who started that rumor? Sure sometimes pad material on the rotor does ocasionally happen but 99% of the rotors I have turned were warped or had thickness variation in the metal and not pad material stuck to the rotor.

My 35 years in the field agrees with you. Can you imagine how many brake jobs I must have done working for a school fleet.I don't remember any instance of pad material causing runout.
You can always set a lathe to cut deep enough to remove metal, THAT doesn't prove anything.


That's what I was thinking.
 
Originally Posted By: jrustles
Another example of someone with far too much regard for their own experience writing an editorial piece.

Pack up and go home guys, we've figured it out. Brake discs cannot and do not warp, it's been some esoteric anomaly causing the problems all along. We just needed some trusted expert to let us all know. Now go out there and buy the cheapest chiense rotors you can find, they're just as good as the top line stuff, just get quality pads.....


Actually I think that's a good idea. Pads with a life time warranty and just buy new rotors when it's time to exchange the pads. Rust will get to expensive rotors in some places even if they are coated. Expensive rotors with no coating?... Now those will rust even faster and you may have spent three sets worth of white box rotors in the time frame.

I still think I'm going to shop for the cheapest coated rotors I can find, maybe centric premium m they are affordable but appear quality.

All you guys saying you didn't see buildup on your rotors.. I thought the point was that the buildup isn't visible to the naked eye. We're you using special equipment when you didn't see pad material on your rotors?
 
Originally Posted By: SLCraig
I have never seen a warped rotor and I have turned some on the lathe personally myself. Change in thickness yes, 100%. Warping, 100% no.


This is one of the major problems in discussing brake pulsation issues. When people say "warped" rotors, what they sometimes are experiencing is thickness variation caused by runout, which then leads to a pedal pulsation.

I think the article posted by the OP almost does more harm then good when people read it. While pad deposits clearly can be an issue in some cases, in many other cases it's either runout in the hub or rotor or another issue. That causes the rotor to wear unevenly and the pulsation starts.

More info on pedal pulsation and runout in this document from Raybestos:
http://www.raybestos.com/wps/wcm/connect...pdf?MOD=AJPERES
 
If I had known it was such a highly debated topic I wouldn't have posted it. It seemed like good information to me. Clearly this is something every one won't agree on.
 
The only way to get pad deposits on your rotors is to come down a mountain with smoking hot brakes and stop or driving erratically enough to get the brakes and rotors extreemly hot.

Normal people don't drive like that. I can set s brake lathe up to just scuff the surface and it will remove magnetic metal and not pad material.
 
Chris142 said:
The guy that wrote that baloney has never turned a disc on a brake lathe! I have and I have seen the metal, not pad material being removed from the disc.

I see stuff like that read often and wonder who started that rumor? Sure sometimes pad material on the rotor does ocasionally happen but 99% of the rotors I have turned were warped or had thickness variation in the metal and not pad material stuck to the rotor.[/quot



I agree with you. Rotors do warp, in fact there is a spec for rotor run out that has to be measured with a dial caliper. Even though the rotor thickness can remain constant around the rotor, run out is another thing altogether. I would dismiss this article as in error.
Click to expand...
 
Last edited:
Originally Posted By: 901Memphis
If I had known it was such a highly debated topic I wouldn't have posted it. It seemed like good information to me. Clearly this is something every one won't agree on.


It's great info that has saved us thousands of dollars on big trucks since we were lucky enough to hear about it. Carroll Smith has forgotten more about braking systems than most of our armchair mechanics will ever know at their best.

The list of companies and racing teams he has consulted for is unbelievable, this guy is a brilliant engineer who knows what he is talking about.

Like I said before, the naysayers still get to keep doing whatever they want!
 
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