With approximately 25k miles on the clock, 3 autocrosses, and 6 track days, my rotors changed sound at the end of the 6th track day. For every single track day, I used Ferrodo DS2500 front brake pads, with an almost immediate swap back to the OEM Brembo pads for street and autocross driving. Cooldown lap as best as I could, rotate the sitting rotors occassionally...

Upon inspecting the rotors after the 6th track day, I noticed I had very small "spider-web" cracks showing up on the inside of the front rotors. The braking power didn't seem to degrade much, but the sound was definitely there. The cracks are worse on the passenger side, with most of my caliper discoloration also on the passenger side.

I replaced the rotors with a beautiful set of Performance Friction rotors just for piece of mind, but I'm wondering if this really is the end of my OEM rotors. What signifies the end of the rotor's life and how much life are you guys seeing our of your rotors? A casual glance around the shop and of the three tracked cars there, three of them did show various signs of cracking.

-Jon

 

I don't have a good macro lens, so we will just have to deal with this... Anyway, here is my passenger side rotor.

-Jon

 

thats relatively normal, and you'll do it to the pf's on your next track day.

only thing to do is go with more cooling.

in regards to your stockers, those cracks are on the surface, and they're still useable. unless you spot a crack thats going deeper, they're useable. The thickness is your concern. If they're ground below the service limit, then naturally, they're done.

 

What WarmPepsi said! The properly way to judge the life of a rotor is to measure the thickness with a caliper. Small spider cracks happen from time to time and are normal. Its the big cracks that you should be worried about, ones that make a clunk noise. I actually change my rotors before they hit the min service limit due to lack of cooling and less material on the rotor to dissipate the heat.

 

The concern I had was the change in noise caused by the cracks. The brake system felt different, but I am always super paranoid right before going to the track. It could have been the absolutely terrible experience I'd been having with Axxis Ultimates on the rear rotors.

The cracks didn't show up on my rotors until a lot of hard running; first track day after having them turned for the first time, actually. I had pad deposits, warping, whatever, but the rotors were pretty sad when I finished the year last season. I came into my first track day this year with refreshed OEM brake parts but they didn't seem to hold up as well as they did all last season. The PF rotors, as far as I can tell, didn't get the cracks after my last track day, but it did discolor the hell out of both calipers that time.

Maybe I'm just getting better and running the car harder?

This conversation was prompted just because I don't know any better. If you buy into what Stoptech has to say, racing rotors get changed out due to heat cycling far earlier than they would be changed due to material thickness. Up until now I've just been running with marginally more power than stock, street tires, and a street/track pad. My last track day had me out there with suspension, same street tires, but more power and an actual track pad. I wouldn't think I'm cycling that stuff nearly as hard as you real track ******, but I can get it hot enough to melt valve stem caps and wheel center caps

-Jon

 

Also, do you guys have any problems with decreasing rotor material causing problems with the stability of the rotors? Warp resistance, thermal capacity, etc?

-Jon

 

As you get more experience, you can beat the car good, regardless of shape and modifications.

The pf's will get the spider cracks.

Running 100% stock, motul fluid and pf 97 pads, i got the stock rotors to overheat (terrible for getting rid of heat). With only upgraded fluid and pads and actually a lighter than stock car, i throughly cherry'd my calipers.

It took me 4-5 events do to that when i started. Took a slow, maybe 6/10ths session, and i'd colored them.

 

naturally, when they get thinner, they can't grab the heat out as well.

However, i had 20+ HARD days on my pf's before i decided to swap them out for a new set (was about halfway down on the dimples).

Decided they'd be a great backup set as they sit.

 

That's nothing!

From 1 day of use, brand new:



like others said already, if the cracks go to the edges and are deeper than surface, that's bad. Also you probably didn't have much material left in the actual rotors anymore so they get cranky easy.