Originally Posted by Snowseeker

Many times once a rotor warps it won't take much to warp it again especially after taking some material off of it.

Originally Posted by njneer1

Don't turn them.....they warp at full thickness

Originally Posted by Stewart_H

Here's some information for you Trey that I've posted in various threads over time regarding "warped" rotors.

Your rotors most likely aren't warping. What's happening is cementite is being formed, caused by hot spots on the rotor which causes the warped "shimmy/pulsation" feel.

The definition of warp is a twist or curve that has developed in something originally flat or straight. That's not what's happening to rotors when it comes to the problems described in the various "brake rotor warp" threads.

The problem is the formation of cementite, sometimes called hot spotting, or black spotting. No amount of turning on a lathe can permanently eliminate this problem.

Hot spots, black spotting, cementite, carbite, hard spots, whatever you wanna call it, it cannot be fixed by turning the rotor. These spots are what causes the brake shimmy, pulsation, warped feeling described in almost every single one of these brake threads. Once hot spots/cementite has formed (aka "black spotting") the rotor is cannot be "cured" of the problem and new rotors are necessary.

Turning can make brakes feel true again, but the shimmy/pulsation will come back in time. Sometimes a very short time.

"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."
StopTech : Balanced Brake Upgrades

A lot of guys will combat this problem with cryo treated rotors because the cryo treating process eliminates the possibility of hot spots to occur in the rotor.

Based on personal experience, as well as threads and posts I've read over the last 7 years here and at TDS, this is a common failing with the stock rotor.

Years ago when I attacked this problem, cryo treated rotors were the only solution that worked 100% of the time. Since then, others have solved this problem with rotors that aren't cryo treated, saving themselves money too because the cryo treated rotors aint cheap.

Here is another excerpt by Carroll Smith in his article "The 'Warped' Brake Disc and Other Myths of the Braking System"

"The term "warped brake disc" has been in common use in motor racing for decades. When a driver reports a vibration under hard braking, inexperienced crews, after checking for (and not finding) cracks often attribute the vibration to "warped discs". They then measure the disc thickness in various places, find significant variation and the diagnosis is cast in stone.

When disc brakes for high performance cars arrived on the scene we began to hear of "warped brake discs" on road going cars, with the same analyses and diagnoses. Typically, the discs are resurfaced to cure the problem and, equally typically, after a relatively short time the roughness or vibration comes back. Brake roughness has caused a significant number of cars to be bought back by their manufacturers under the "lemon laws". This has been going on for decades now - and, like most things that we have cast in stone, the diagnoses are wrong.

With one qualifier, presuming that the hub and wheel flange are flat and in good condition and that the wheel bolts or hat mounting hardware is in good condition, installed correctly and tightened uniformly and in the correct order to the recommended torque specification, in more than 40 years of professional racing, including the Shelby/Ford GT 40s – one of the most intense brake development program in history - I have never seen a warped brake disc. I have seen lots of cracked discs, (FIGURE 1) discs that had turned into shallow cones at operating temperature because they were mounted rigidly to their attachment bells or top hats, (FIGURE 2) a few where the friction surface had collapsed in the area between straight radial interior vanes, (FIGURE 3) and an untold number of discs with pad material unevenly deposited on the friction surfaces - sometimes visible and more often not. (FIGURE 4)

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."
StopTech : Balanced Brake Upgrades

EBC, a very well respected brake company also has information about Cementite on their EBC web page.

Stewart

Originally Posted by AlaskanEx

its a band aid for the rotors. after a few factory sets i finally spent the money on powerslot rotors cryo treated. have not has an issue after over a year. very happy!


for bedding, i slowly run up in speed then brake pretty hard. IE 20,30,40,50,60mph dont stop though come down to a roll! i get up to about 70mph then a hard almost stop and call it good. it has worked well for me in the past and on this set of rotors.

Originally Posted by Turfzilla

Just get a set from Orielys with lifetime warranty. I can not remember but I think they were under $100 for the set.