Stock steel rotor life expectancy?

[robertg]

Just a random question:

How long should I expect my stock rotors to last on a street driven only car.

My car is an early production 15 M3 with 30k on the clock.

[CanAutM3]

Way to many variables at play to even attempt an answer.

[MNoob]

Originally Posted by CanAutM3

Way to many variables at play to even attempt an answer.

46,837 miles. duh.

[Woodengun]

Driving style/conditions have enormous affect on brake life. I'm at 62k miles and approximately halfway through rotor life.

[robbo mcs]

One thing is that the dealership will often replace them before they are minimum thickness. If they are changing a set of pads, and the discs are worn, but still over the minimum they often replace them anyway.

They should last longer than a set of front oem pads for sure

[Lojs]

Originally Posted by robbo mcs

One thing is that the dealership will often replace them before they are minimum thickness. If they are changing a set of pads, and the discs are worn, but still over the minimum they often replace them anyway.

They should last longer than a set of front oem pads for sure

What is the minimum thickness?

[Woodengun]

If you look at the rotors, there are indents at the outer edges. The indents appear to be approximately half the thickness of the ring. I would think these are a visual indicator for when rotor thickness has reached minimum. By my estimation I'm about 1/2 through rotor life so I've worn through 1/4 of the ring thickness.

Other warning signs such as cracks through the entire thickness preempt a wear indicator as above.

If you're not willing to work on the car a bit yourself, you've got to go with what the service person tells you. If you don't trust that person, time to find a shop you do trust. Or time to roll up your sleeves and get dirty. Brake work is really really really dirty. Remember that auto repair shops are regulated by the states and most states require a shop to give you the old part if you ask for it. So if you aren't sure you can ask the shop to give you the old rotors and you can inspect them yourself. If the shop refuses to provide you the old parts - for certain time to find a new shop.

[robbo mcs]

Originally Posted by Lojs

What is the minimum thickness?

I don't know off the top of my head. However, it is always marked on the disc so a mechanic changing pads can see it and measure the disc. Usually it is stamped on the central hub part, in mm.

Interestingly carbon discs work differently. They do not have minimum thickness but a minimum weight.