simple way to gauge the warp in your rotor. Tape a zip tie or something to your front fender and position it close to the rotor that concerns you. As the wheel spins, you can hear and see the oscillations in the rotor as the face moves toward and away from the edge of the zip tie. This method will not provide a numerical measurement of how large the deformation is, but it will give you a good relative indication for where the rotor is warped. I straightened a rotor using this method and it worked beautifully. The warped portion was roughly 3-5 mm out of true from the rest of the rotor. Let me know if you have questions, I can send pictures of the setup.