Can't see how you can say runnout is not caused by heat. I will tell you from expierence that if the rotors are not tempered correctly to begin with that when hot and then get queched as going through a puddle they will have runnout. So to say that runout is not due to heat, totally false! From racing expierence you would never turn a rotor due the loss of heat sinking! Years ago turning was an accepted practice not so much anymore! hy because they are much cheaper now to replace, and the best way to do it is on the car. Which a lot of shops don't have the on car klathe setup. Even though some still turn rotors, if the original problem still exisits,as in tempering, it will come back!
Geez, where do I start. First, any tempering is completely overridden when the rotor is heated very high and quenched. And would be re-tempered anyway the next time the rotor was heated that high and allowed to cool slowly. Second, let's pretend your right, and somehow heat allowed the rotor to "warp" and generate some pure runout as you describe, this would NOT cause the pedal to pulse, as the distance between the pads would remain constant and NOT result in the pedal shudder described by the original poster. Pure runout in rotors, is rarely noticable, it is when the runout of the front and back faces are different when the problems arise. This resulting thickness variation is caused by one of two things, uneven wear of the rotor, and two uneven deposition of pad material on the surface. Occasionally, uneven pad material deposition or uneven rotor wear can be caused by local hotspotting of the rotor face leading to a hardened area that wears differently than the rest of the rotor, but its still wear, and definately NOT distortion due to heat as you describe. This runout/distortion due to heat, often called warped rotors is extremely rare, and very difficult to make happen. So much so that its nearly a modern myth, despite many mechanics swearing by that diagnosis out of ignorance. The problem is, the equipment required to measure it properly and prove what really happened, is so expensive, only specialized brake testing companies and OEMs have it, so it never gets debunked in public circles. I have personally spent many many hours in my professional career using such equipment, and reviewing the resulting data.
You are right, that people turn rotors less often these days, largely becuase new rotors are cheaper, not because there is anything wrong with a turned rotor. Turning a rotor removes no more material than normal wear does; the OEM min. thickness specification very easily and clearly sees to that.
And who said anything about turning a race rotor? The OP can correct me if I'm wrong, but I'm pretty sure he's not doing any competitive racing in this particular car. From MY racing experience, I've never had a reason to turn a rotor, despite the fact the race rotors I've used were FAR more prone to the high heat and quenching scenario you described above. My race rotors typcally wear out before needing anyhting like being turned, besides, they are generally slotted, and I wouldn't bother turning a slotted rotor as the risk of breaking the cutting head is pretty high.
The bottom line is, you've got your metallurgy wrong, and you're applying an old assumption to symptoms you've seen simply because other people do too.
