I have the truest disc rotors in the steel city.
Its all thanks to the crazy Park Tool Disc Truing Gauge(DT-3), Disc Truing Indicator(DT-3i) and Rotor Truing Fork(DT-2).
Another view of how it attaches.
This tool attaches with an alloy rod that goes through one of the holes in the Park TS-2 truing stand and then a post that goes on with quick a release.
The disc truing gauge has a threaded rod with a button on the end that you position close on the disc to check for truness of the rotor.
You bend the rotor in to shape using the rotor truing fork, which is just a hunk of aluminum with a slot cut in it, until it stops rubbing.
But you can take it even further and use the gauge. Oh damn this thing is nice. It is a gauge that will show in 100th of a millimeter how far out of true the rotor is. Its pretty amazing.
Park has a great how to on truing rotors and using these tools:
