[compguy36]

This is my first full year of tracking a car. Learning a ton. One thing I've asked folks at events is when you know it's time to replace the rotors. I've gotten a wide variety of answers. Hoping someone here can help. I'm 10 days so far on my M2C running Pagid Yellow RS29's. Starting to notice cracks around the cross drilled points on the face of the rotors.

Secondarily have people noticed increased wear based upon pad choice.

[eeyang92]

Originally Posted by compguy36

This is my first full year of tracking a car. Learning a ton. One thing I've asked folks at events is when you know it's time to replace the rotors. I've gotten a wide variety of answers. Hoping someone here can help. I'm 10 days so far on my M2C running Pagid Yellow RS29's. Starting to notice cracks around the cross drilled points on the face of the rotors.

Secondarily have people noticed increased wear based upon pad choice.

The on the tech sheet of the group I run with it usually says you have to make sure there aren't any cracks in the rotor.

[joseyu]

Some small cracks in drilled rotors for tracked cars are normal. Just make sure none of the cracks are at the outer edge of the rotor or connecting the drilled holes, otherwise you should replace them. If you are planning to track the car frequently, I could recommend that you ditch the drilled rotors and at least go with something slotted or even J-hooks or Brembo type-3. Drilled rotors are not normally recommended for extensive track work because of the cracking at the holes. I am not sure who is making replacement rotors for the M2C. Maybe Girodisc?

[M2joey]

Originally Posted by compguy36

This is my first full year of tracking a car. Learning a ton. One thing I've asked folks at events is when you know it's time to replace the rotors. I've gotten a wide variety of answers. Hoping someone here can help. I'm 10 days so far on my M2C running Pagid Yellow RS29's. Starting to notice cracks around the cross drilled points on the face of the rotors.

Secondarily have people noticed increased wear based upon pad choice.

Seeing small cracking is normal, as mentioned. Below is a great article, which the same can be said for the M2C brakes.

https://www.bmwblog.com/2014/04/13/n...-brake-system/

This being your first year tracking your car you will most likely give your brakes the most punishment. The Pagid RS29 is a great pad although are known to be a little rougher on rotors. The two biggest things that will cause you to wear and abuse rotors at this point is your braking technique and traction control. In short, as you learn, and at some point run with DSC Off your brakes will stay much cooler and not wear, etc. like they will now. Heat is the killer.

I suggest letting a performance shop or BMW dealer help you determine when the replace the rotors, at this point. There is not one answer as there are so many variables at play:

1 - Drivers braking technique - most important
2 - DSC On or Off - On will heat the brakes up much faster, as you start driving faster. It will first cause the rear pads and rotors to heat up fast and wear fast. When you run with DCS Off your fronts will wear twice as fast as the rear pads, general speaking. Don't rush turning it off if you still run with it on.
3 - Pads - which pads, when were they installed, mixing of pad materials, etc. It is best to run a single pad type per set of rotors. Switching of OEM pads back and forth with after market can create mixing of compounds which can create issues (ie bad vibrations, over heating, etc.)
4 - Tracks that you are driving on - some are much tougher on brakes then others

Personally, I was able to get about 25 track days in on my front rotors last year. Still have the same rear rotors on, about 10 (4 x sessions per day) days in this year so far, four different tracks. I drive with DSC Off.

Hope this helps!

[dvas]

Originally Posted by compguy36

This is my first full year of tracking a car. Learning a ton. One thing I've asked folks at events is when you know it's time to replace the rotors. I've gotten a wide variety of answers. Hoping someone here can help. I'm 10 days so far on my M2C running Pagid Yellow RS29's. Starting to notice cracks around the cross drilled points on the face of the rotors.

Secondarily have people noticed increased wear based upon pad choice.

Small cracks around the drilled holes are normal and nothing to worry about. Just watch them to monitor whether individual cracks are connecting or meeting the edge. At that point the rotors should be replaced. You should be able to get about 30 days on them before they need to be replaced.

[5.M0NSTER]

Thread revive. This is what my rotors are looking like after 7 days and ~20k miles of street use. What do you guys think? keep rolling or start looking for replacements?

I'm leaning towards monitoring the larger cracks, but keep going. I have 1/2 of the material left on the PFC08 pads still.

[chief1richard]

Originally Posted by 5.M0NSTER

Thread revive. This is what my rotors are looking like after 7 days and ~20k miles of street use. What do you guys think? keep rolling or start looking for replacements?

I'm leaning towards monitoring the larger cracks, but keep going. I have 1/2 of the material left on the PFC08 pads still.

Looking at the edges you seem to have some good wear of thickness of Rotor. I don't know what the minimal thickness is, but you can measure thickness with micrometer as far as thickness goes. Cracking is another issue. Hard to see all of the Rotor. My son was a passenger in his Instructors WRX at Palmer 's Motorsports Park, when they were excelerating coming out of Turn 9 (left turn) and the right front 5 Spoke Wheel separated at the 5 spoke connections, and flew into the woods. They went through 2 tire walls at 70 mph totaling WRX. Both were OK, but sore thanks to HANS Devices. Thank God the spokes didn't dig in while taking the turn and flip car. The only way to see how far cracks go is with UV light and Dye. It's best to be on the safe side if it were me and get new Rotors. Who knows how far those cracks go.

[bentom2]

Originally Posted by 5.M0NSTER

Thread revive. This is what my rotors are looking like after 7 days and ~20k miles of street use. What do you guys think? keep rolling or start looking for replacements?

I'm leaning towards monitoring the larger cracks, but keep going. I have 1/2 of the material left on the PFC08 pads still.

My last set of new rotors looked similar after just a few track days days and street miles. I’d just check thickness with a micrometer or caliper as Richard mentions, but keep running them until you get close to minimum thickness (it’s etched on the hub in mm), or you see a crack reach or getting close to the inner or outer edge of the ring face. In my case, they reached minimum thickness before the cracking got to an edge. That was after around 40 track days and 20k miles with Pagid RS29s.

[dvas]

Originally Posted by 5.M0NSTER

Thread revive. This is what my rotors are looking like after 7 days and ~20k miles of street use. What do you guys think? keep rolling or start looking for replacements?

I'm leaning towards monitoring the larger cracks, but keep going. I have 1/2 of the material left on the PFC08 pads still.

In terms of cracks, those rotors are completely fine, I would run without issue. I replace my front rotors roughly once every two years and they look way worse than yours.

[VisualEcho]

Originally Posted by M2joey

Completely normal.

This is a great article about the M Sport brakes from a BMW engineer -
https://www.bmwblog.com/2014/04/13/n...-brake-system/

This.

[5.M0NSTER]

Thank you for the feedback gentlemen.

[5.M0NSTER]

Final update from my side. Had the car serviced by BMW Dealer in Heilbronn. They measured the rotors as 2-3mm thicker than minimum, and told me to keep running on them. Thanks for the suggestions everyone!

[M2joey]

Originally Posted by 5.M0NSTER

Thread revive. This is what my rotors are looking like after 7 days and ~20k miles of street use. What do you guys think? keep rolling or start looking for replacements?

I'm leaning towards monitoring the larger cracks, but keep going. I have 1/2 of the material left on the PFC08 pads still.

They still look "good", and some cracking is normal as well. I have around 55 days on my rears, with no cracks. And of course if you are driving in "any" mode except DSC Off, good chance you will be overheating the rear rotors, and certainly would be on a track. The TC will be "kicking in" adding extra heat in addition to your braking technique. Well, there is more than one answer to that topic too.

[chief1richard]

Originally Posted by 5.M0NSTER

Final update from my side. Had the car serviced by BMW Dealer in Heilbronn. They measured the rotors as 2-3mm thicker than minimum, and told me to keep running on them. Thanks for the suggestions everyone!

2-3 MM thicker than minimum? 28.4 MM is minimum. 30 MM is new. Sounds like your rotors are adding thickness as you wear them.