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Drums and rotors do in fact warp. As others, Ive spent enough time behind a brake lathe to know that. Anyone that says they do not warp have no idea what they're talking about. Min thickness is listed on the rotor, you make your cut then measure.

Flywheels warp too, so do clutch packs.
 

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I put a run out gauge on them and quantify the warpage.
 

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Discussion Starter · #48 ·
Has enough people in here convince you to rotors warping?
I never said rotors never get warped (See post #28). Neither did the article I linked to. I just called into question your assertion that all of the rotors you've machined over the years were all warped, as opposed to being thicker from deposited pad material. From what I've read, both conditions do occur. Only by putting a caliper on the rotor at multiple locations and comparing the measurements would you be able to tell which condition the rotors suffer from. The solution is the same, but the causes are different, and the issue with deposited pad material is preventable with proper break-in of new rotors and pads.
 

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Discussion Starter · #50 ·
Ive never seen brake pad material (fuse) to rotors or drums. Thats on motorcycles to tractor trailers and everything in between.
I have, although it's not as obvious to the eye as you might think, especially with metallic pads. Pulsing brakes are a classic sign of this condition. Mine originated with an emergency braking situation and actually got worse over the next months.
 

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Brakes pulsate, I buy new rotors. I don’t care whether it is brake pad deposits or warpage.
 

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Discussion Starter · #52 ·
Brakes pulsate, I buy new rotors. I don’t care whether it is brake pad deposits or warpage.
Me too. As I said, I posted the article about the brake pad deposits so people would be aware that proper bedding/break-in can prevent this problem. Also, many times warped rotors cannot be turned, because they would be too thin if you did, but ones with deposits could be. Granted, I can't find a machine shop around here that even turns rotors as a regular thing, so the prices to have it done are more than new rotors. There's also far less hassle and downtime to replace them.

I replace the rotors whenever the pads need replaced. Supposedly, you can change rotors every other time the pads are changed...if they're not too worn down/thin, warped, have pad deposits on them, and if they don't have grooves, and if half a dozen other things that I don't care to check are true...not worth the hassle to inspect them that closely, when it takes 5 minutes longer to replace the rotors while I have the calipers off, anyway. Of course, since I plan on that from the beginning, I don't replace the pads until the pad material is completely gone. I trim, remove, or bend the little warning tabs, so I don't have to worry about them squeaking until I hit the metal of the backing.
 

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I have, although it's not as obvious to the eye as you might think, especially with metallic pads. Pulsing brakes are a classic sign of this condition. Mine originated with an emergency braking situation and actually got worse over the next months.
Let me preface by saying (again) Ive worked on many cars/trucks. Also ran a fleet of 18 vehicles (which itself is another ballgame) But if what you and that web page are saying is true, rotors would all warp before they wore out. Which is not true. 99 times out of 100 the reason for warped rotors is heat. Riding the brakes, bad caliper, line or pins, etc. The vehicles in my fleet would run 500-800 miles per day. Id install probably 5-6 sets of pads on the same set of rotors without any warping (or the mysterious buildup as you say). Just tossing the rotors from wear.
And this wasnt in fly-over country USA, but NY/NJ with plenty of traffic.
 

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If I have a choice, I buy expensive pads and cheap rotors. Then they are both shot at the same time.
 

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99 times out of 100 the reason for warped rotors is heat
I'm guessing 9 years as an OEM brake engineer doesn't count for much compared with all the "experience" posted here but you simply can't get rotors hot enough, with normal usage, to metallurgically cause them to warp. But we really didn't bother testing the really cheap crap so I cant disagree with all the experts here!
 

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I'm guessing 9 years as an OEM brake engineer doesn't count for much compared with all the "experience" posted here but you simply can't get rotors hot enough, with normal usage, to metallurgically cause them to warp. But we really didn't bother testing the really cheap crap so I cant disagree with all the experts here!
I'm finding a lot of OEM rotors warping. I also never had a replaced rotor warp at all.
 

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I'm guessing 9 years as an OEM brake engineer doesn't count for much compared with all the "experience" posted here but you simply can't get rotors hot enough, with normal usage, to metallurgically cause them to warp. But we really didn't bother testing the really cheap crap so I cant disagree with all the experts here!
"Heat" meaning excessive heat from a bad caliper, line, pins, etc. Will in fact warp a rotor.

I had a problem with the ABS module on a E250 van not letting all the pressure return after braking, warped brand new rotors.
 

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Ive never seen brake pad material (fuse) to rotors or drums. Thats on motorcycles to tractor trailers and everything in between.
It does happen to an extent, I believe it's why we end up seeing the glossy finish on rotors and while it may account for some thickness variation, I've had enough rotors on a lathe to also see that metal gets removed not just adhered friction material to get a rotor flat again.

Mostly when I see pad material fused to a rotor it's because a vehicle hasn't been driven and some sort of reaction happens between the friction material and the rotor leaving a noticeable build up(real common on 07-16 Honda CR-V rear rotors). As a professional tech we would just resurface them but realistically you could grind the build up off with an abrasive disc on an angle grinder. Not sure how long that fix would work/last though.

The other thing I have noticed when they do leave a build up from sitting, even when you resurface them you can get the rotor flat but still see the outline of the brake pad where the build up was.
 
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