i understand the physics and mechanics of a thin rotor. i also think that many times dealerships and repairs shops push for new rotors when the old ones are still very much within the specs. as a result, money is wasted when it could be used elsewhere. that was the intent of my post.

 

The reason shops will recommend new rotors
1. The shop doesn't have a brake lathe to turn them (smaller ma and pa shops)
2. They are above discard but below machine to (possibility of warpage)
3. The new pads are a different friction material: i.e.switching from semi-metallic to ceramic or organic or vice-versa
4. The mechanic is too busy or lazy to turn them
5. To elimate comebacks - the customer returning complaining of noise or vibration
6. Places like Midas for example only give lifetime warrantyon the padswith new rotors (they also charge $25 for the brake inspection if you refuse to do the work)
7. Sometimes the labor cost to turn them is about the same asa new one

Yes, there are many places that will take advantage of people, but that isn't EVERY shop. Just like going to the doctor, you can always get a 2nd or 3rd opinion.