Pretty straightforward question that I'm not clear on. How do you know if the rotors need to be replaced? Alternatively you could always do the rotors when you replace the pads.

 

feel the rotors, obviously while they are cool, if you feel a "lip" developing on the outer edge start thinking about rotors

 

You replaced them when they can't be "turned" and still be at least spec. Note: I've had quite a few rotors develop a lip at the outer edge and still have enough meat to be turned.

When replacing pads, at a minimum, take a Scotch-Brite pad to both sides of the rotors (so the new pads can lay down their own film ... i.e., "bed"). If the rotors have grooves, etc, have them turned. If they can't be turned and be at least spec, replace (see first paragraph).

 

Here's your answer

 

I will be doing pads and rotors soon for the first time on the car. i asked about cutting the rotors and 2 places told me to replace the rotors when replacing the pads because you cant cut high performance brake rotors.

 

If there is any sort of warping what so ever I replace my rotors. I learned the hard way that turning them only fixes it for awhile if they've warped already.

 

Were these places that turn rotors or places that sell rotors? You can turn any rotor, even slotted or drilled, although it's much harder to do a floating-type. Maybe you have (or they though you have) an MR...?

 

you will know when you need to replace the rotor,
when you see them like this

 

Find out the cost of the original factory rotors before you just scrap them, they're petty damn good rotors that will last through at least 2 sets of pads. Even a small lip isn't reason enough to cut them, I pad slap mine all the time with no problems. The thinner the rotor the faster they heat up and crack.

 

OEM 2-piece rotors for MRs are on the pricey side. This is my first time owning a car where the rotors are a significant investment, and I would rather not replace them if they still have life left.

I should have been more clear in my original post. There are clear signs of rotor failure such as warping, cracking, steering vibration, etc. These are the results of misuse or poor maintenance, and should have been replaced prior to failure.

What I am really looking for is a predictive and measurable indicator to prevent issues from manifesting into a greater problem.

 

Warped? Doubt it very much, cracked, maybe post a picture.

Read this before you do anything stupid. http://www.stoptech.com/technical-su...nd-other-myths

 

I was talking to the pictures and comments in the thread so far.

A lot of comments like if they look like the picture below its time.

 

Ultra-vented rotors, FTW!

 

Brake Disc Minimum Thickness
Front 30.0 mm (1.18 inch)
Rear 20.0 mm (0.79 inch)

Brake Disc Run-Out
Front 0.06 mm (0.0024 inch)
Rear 0.08 mm (0.0032 inch)

 

Thanks!