When to replace stock iron rotors?

[m3f80sf2ny]

My car has about ~16000 miles and 16 track days. The front rotors(non-CCB) are starting to show signs of minor ridges and grooves. I am running RS29s and not aggressive race pads.

How many track days do the stock OEM rotors last for you guys?

What are some of the signs that would suggest it's time to replace the rotors?

And what are some good replacement options if I want to stay with stock calipers?

[CanAutM3]

I find the OE rotors to be pretty stout. I changed my front rotors after ~20k miles and 30+ track days. Rears are still plenty good. For me, the sign for replacement is with the cracks in the rotors: when cracks start to interconnect two cross drill holes together, it's time to replace. If a crack reaches to edge of the rotor itself, replace immediately. The nature of cross drilled rotors will inherently cause ridges and groove to form on the surface of the rotors. Since I don't find that those ridges and grooves have much negative impact on the brakes performance, I don't mind them. I would also recommend never having your rotors turned/surfaced.

[m3f80sf2ny]

Thanks for the helpful feedback.

[Candide13]

Originally Posted by CanAutM3

I find the OE rotors to be pretty stout. I changed my front rotors after ~20k miles and 30+ track days. Rears are still plenty good. For me, the sign for replacement is with the cracks in the rotors: when cracks start to interconnect two cross drill holes together, it's time to replace. If a crack reaches to edge of the rotor itself, replace immediately. The nature of cross drilled rotors will inherently cause ridges and groove to form on the surface of the rotors. Since I don't find that those ridges and grooves have much negative impact on the brakes performance, I don't mind them. I would also recommend never having your rotors turned/surfaced.

So you don't mind about the rotor thickness going below spec? Or do you get connecting cracks before that happens?

I wonder because my front rotors are near the theoretical min thickness (28.4 mm, I think), but otherwise look and perform well.

[CanAutM3]

Originally Posted by Candide13

So you don't mind about the rotor thickness going below spec? Or do you get connecting cracks before that happens?

I wonder because my front rotors are near the theoretical min thickness (28.4 mm, I think), but otherwise look and perform well.

To be honest, I never really bothered about min thickness. The few times I did check, I had interconnecting cracks before min thickness was reached.

[The Choosey begger]

A good time to change your rotors when they become glazed and you dont have enough material to resurface em like i did.

[Suds]

Your rotors look pretty virgin, with PCA as long as cracks don’t go between holes or to the edge of the rotor you are good.
I have done at least ten track days since my rotors showed cracks.

[Pic18]

Originally Posted by Candide13

So you don't mind about the rotor thickness going below spec? Or do you get connecting cracks before that happens?

I wonder because my front rotors are near the theoretical min thickness (28.4 mm, I think), but otherwise look and perform well.

If you are at or below the min thickness the rotor is more prone to cracking and will not dissipate heat as well, likely leading to faster pad wear. Really no reason to go below min thickness.