My 2011 R56S needs front pads. I am buying both front and rear EBC Red Stuff pads, but am not sure if I should attempt to machine the rotors on a brake lathe, or just pad-slap it. Is there (generally) enough metal on the stock (not warped) rotors for a little cleaning up of the grooves? I have not gone metal-to-metal. I will try to post a pic of one of the front rotors to give some idea of the grooves I am seeing.

 

For about $30-45 (nothing fancy, but a decent oem, painted hat equivalent like a centric premium) each you can get NEW rotors....if they are more $$, IMO, might be with getting them cut, but since rotors are CHEAPER than the pads, why risk wrecking a set of pads....

 

You can certainly have them turned, but be aware that there is still a minimum rotor thickness requirement, each side and total.
Having once been a garage monkey, (many years ago) and done a zillion brake jobs, to me, it's easier and cheaper to just replace the rotors. Discs and pad replacement is just a bolt on job now. Nothing exotic.
New pads will bed into a used rotor. It may be a little noisy at first, but they will do it. Lots of people do it, everyday. It may not be the preferred, or recommended, method, but it will work.
The problem may come if you have a shop do the work for you. They may not do it due to consumer protection laws.
When I used to do brakes, everybody thought we were ripping them off by having the drums and rotors either turned or replaced. In actuality, buried in our state consumer protection laws, was a requirement for a minimum pad to surface contact, and the number was 100%. No way you could guarantee 100% without replacement, or turning. ( This is why some of the national chains offer "free brake system inspections".)

Me personally, I would just replace the rotors. It's too easy and cheap not too.You paid for nice pads, might as well get the full benefit from them.

 

Buy a higher quality rotor, preferred is high carbon steel. These OEM rotors are just too soft, Centric 125 rotors are a higher quality rotor.

 

To answer the op's question, measure the rotor. The minimum thickness is stamped on the rotor. Then figure out if there is enough to turn them. (There probably isn't)

So, suck it up and buy new rotors. They really are a consumable item. You'll like the red stuff pads. I do...

 

Looks like new rotors, then. Most likely Centric. Thanks, guys.