Toyota-Lexus-Subaru-Honda Brake Rotors–Machining/Replacing

Machining Brake Rotors Some shops always insist on either replacing or machining the rotors and drums when replacing brakes. I’m comfortable with a couple of approaches here.
I’m comfortable machining them, and believe that the final outcome will be more certain to be the best brake job we can do. We machine the rotors on the car, so the final effect smoothes out any effects that might be there as a result of the hub not being perfectly true.

The two rotors at that point are very flat and have an ideal texture for breaking in the new brakes. Also, when the rotors have been freshly machined, the new brakes are less likely to squeal. If a customer expresses sensitivity to brakes squealing, then I’m heavily biased toward machining them even if there are no other problems with the rotors.

My two award-winning master technicians with years of experience both prefer to machine the rotors in order to assure the best brake job with the least possibility of customer dissatisfaction.
Having said all that, if the rotors visually look ok—flat, not worn irregularly—and seem to be symptom free without any shuddering or shimmying when braking—I’m comfortable reusing them without machining them as long as the customer isn’t concerned with the possibility of some brake squealing.

In this instance, there is the possibility that we will believe the rotors to be symptom free, but be unaware that the rotors do in fact have some symptoms at higher speeds or when going downhill after braking enough to get hot.

As far as the best-case braking in the first instance (with rotors machined) versus the good-enough braking in the second instance, I’m not convinced that most people would feel the difference, especially after a couple of days of the brake pads seating in.

One further argument in favor of not machining rotors that appear to be in good condition is that it removes metal from the rotors and effectively shortens their lives. There is a legal minimum thickness below which it is illegal to machine them. Every machining moves them a little closer to that legal limit (as does normal wear through normal use).