yarin

<a href="http://www.stoptech.com/whitepapers/warped_rotors_myth.htm" target="_blank">http://www.stoptech.com/whitepapers/warped_rotors_myth.htm</a>

What do you guys think about this? I believe most of it. But I still think rotors do warp. The average person doesn't know that you have to break a brake pad in. This is good stuff, it is worth reading.

Tabor

I don't like myth #6 either.

TheJonesBoy

If this was written by the Carroll Smith that I am thinking of, it definately demands some consideration. I have seen rotors on Formula SAE cars warp considerably. I mean take them off and put them down and they don't lie flat type warping. I have seen warping on my VW discs only when machining them.

Perhaps he has been working with quality parts that have better production tolerances, and less internal stresses? Not to mention, most racers use highly abrasive pads that may machine out the warpage as it forms?

doyle

Even if it is Carroll Smith, I think he's full of crap in myth #1. Try riding around in my old 83 944 and tell me the rotors aren't warped.
Even after I installed rotors, pads calipers, lines and fluid, all brand new, and yes, properly bedded the pads according to specifications, the rotors still warped. You could visibly see it. I went through 4 sets of rotors in 28 months.

As for myth #6, that was the practice at the Honda dealer where I worked. In theory, if you let the fluid level just drop with the pad wear, when you replaced the pads, the level should go back to full, if not, this would be an indication that there was a leak in the system.

I want to beleive what Carroll Smith says beacuse of reputation, but I can't swallow the notion that rotors don't warp. It's hard to beleive that one man is right and an entire industry is not.

billybones

Nice article, from what he says it is not a true warp. just softer material from the disc being erroded away while the ceminite collecting material form the pad which is unseeable to the human eye..Thus the foot print. and a resurface does not always do away with a reaccuring warp... cause the ceminite stays and collects more pad stuff.. at the foot print.. I belive it. I have resurfaced a lot of discs.. and 7 times out of 10 they come back a short while later... this was back in the days that you had a lot of thickness to deal with... maybe this was the reason that new rotors .. well last 15 years are not so thick.. so the ability to resurface has been removed..

billybones

I wonder what the ceramic rotors do?

Dave

I have to wonder why anyone would attempt to measure a rotor with a caliper to see if it is warped. I would have to believe that runout would be the correct measurement to take.

jim968

I'm not sure I agree with his warped rotor theory, but I will read it a few more times & think about it. I do agree with the rest of it pretty much, tho' I'd feel dam' odd knowing I was driving with low brake fluid for any length of time. Besides, the post '85.5 cars have a more direct indication of pad wear. I really like his explaination of break-in for new pads & rotors. I've seen a lot of conflicting info on this. His seems to make good sense.

Jim, "Work thou not on energized equipment, for if thou dost, thou buddies will surely be buying beers and consoling thy spouse in other ways not generally acceptable to thee."

fletch.

Number one is BS, most of the rest in non sense as well. Put a rotor on a lath to prove it's warped. Done it many times. Pad transfer is easy to spot, and it a totally different feeling.


Number 6 is amazing in it’s foolishness, not checking brake fluid or toping off is nuts. Many modern cars use traction control that relies on the accurate brake fluid level which is never mentioned.

Water944t

hmm...this should be posted over on Corner-Carvers, let them chew its *** ragged a bit and hit us all with the "Smart-Stick".

Manning

I am not so sure I would call it BS. Putting a rotor on a lathe to determine runout is simply going to prove you have surface irregularities, either from deposits or from the rotor surface settling into the voids between the vains as mentioned in the article. You would have to measure runout of a "warped" rotor by measuring how much the center line of the circumference of the rotor deviates from side to side in relation to a fixed pointer.

Mark Parker

Whether because of "warping", hub distortion, or friction material deposits the end result is non parallel surfaces or excessive runout, and the cure is the same; resurface to restore to spec. The big problem is that removing any material from what is already likely to be an undersized heat sink will only lead to the rapid reappearance of the problem, just as the author said. On the whole, I find this article very informative, and for the most part I agree with him. Being involved with fleet maintenance, this is one of the biggest headaches we face everyday. I plan to print this and share it with management, because some of the info about pad materials and proper bedding procedures could be helpful to our operation. As far as myth #6, I totally agree. If you inspect and replace the pads when the brake indicator lights due to low fluid level, and simply push the pistons back into their bores you'll find the fluid level back at full. It's a simple and effective method of tracking both pad wear and fluid loss due to leakage with one reliable system. I assume that some of you open the bleeders when pushing the pistons back (which isn't necessary)and never get the overflow of brake fluid from the reservoir.

fletch.

On the runout issue, the claim was made that rotors DO NOT WARP. Simply not true, I see it all the time, other factors may be present, but to say rotors do not warp is inacurate.

abduln

With all due respect to Smith, I hold him in very high esteem, warped rotors are definitely a reality. However a pulsing pedal is not always caused by a warped rotor; the same symptom could have several causes.

I have personally had to deal with several warped rotors, verified on an lathe with an indicator and a mic.

As for checking runout, if I recall correctly that will only tell you the out of roundness of the rotor. You test runout buy running an indicator on the edge of the rotor and spinning it, which gives your TIR. I believe what you really want to check is out of flat with the indicator on the rotors faces, which is what I have always done. Perhaps I am not using the terms correctly, I am not a machinist, but that is the terminiology my associate, who is a machinist, uses.

Regards,
Abdul

billybones

I have only one thing last to say on the runout stuation... do you check both sides of the rotor prior to resufacing? is the runout equall to one side to the other? the only reason I could see that a rotor would be totally pushed out of alignment would be that the casting was so over heated that at the point the metal was soft. and your caliper did not slide into a central position while clamping down. and actually reshaped the casting. Not likley.. and if it did.. you need a better set up.. it is not to what the needs are...IMHO..