typically I like doing a quick cut followed by a slow cut to correct the runout usually occuring in most rotors.
"warping" is usually a result of uneven pad material that accumulates on the rotor and not the metal heating and cooling as most people think. As the brake pad torques on the rotor you feel these "hills and valleys" or parts of the material that have more friction than others.
I like taking off a few thousandths just to start with a clean slate to break in new pad material.
if you just replace pads you will likely end up with an uneven transfer layer on the rotor because of different pad material/temps on the rotor already existing.
if you can't do it yourself, most shops will offer this service if you just ask. The only downfall to machining your rotors is ending up with less of a heat sink because of having less metal to soak up the heat.
The best solution to all of this is to buy new rotors everytime a pad change comes up. This can be costly to some(most compact rotors are cheap) which is why most people will only change pads or do pads and machine the rotors.
I always machine my rotors/drums when installing new pads but it helps that I have access to a brake lathe in my shop. Andy, fast then slow cut? Thats so Ammco! I love the 1 pass positive rake Accu-Turn for my money, it also does flywheels
A little runout is a good thing. It keeps the pads away from the disks and prevents them from dragging. I have a Ford Taurus which had a rotor that felt warped but the pulsing would come and go for no reason. After a while I had to replace the wheel bearing on that side and the problem with the disk also went away.
Just did the rear brake pads yesterday. I didn't touch the rotors and car brakes good. Well anything was the better than I had before; the left rear caliper was seized up pretty bad, so I had to change it out.
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