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Thread: How many days on track are before you crack rotors?

  1. #1
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    How many days on track are before you crack rotors?

    Just cracked my first rotor, which I consider a significant milestone in my driver development. They were brembo blanks, 4 days with Hawk Blue 9012 and 4 days with PFC-06, on a stock(ish) e36 328is. I just bought cheapo Meyle replacements to see how they last...

    Curious how many days you guys are getting out of rotors.

  2. #2
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    Micro-cracks or a full edge-to-edge failure? 8 days seems a bit short. Smaller the rotor, the shorter the life (everything else constant). Pads, track, braking skill, all make a big difference.

    I'd estimate I was getting 10-12 days on my stock E3 M3 rotors, and 15-20 days or so on my upgraded E46 M3 rotors (on E36 chassis). But before full failure.
    Last edited by aeronaut; 05-24-2018 at 12:08 PM.

  3. #3
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    I race an E36 M3 on stock M3 brakes with ducting and go more than a season without cracking a rotor. By cracking, I mean a full depth crack with displacement.

    Micro cracking at the surface occurs quickly and I monitor it, but 4 days with a full depth crack is very short.

    Are you running ducting to your rotors?
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  4. #4
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    I have never cracked a rotor, on a not at all stockish 328is (230whp)... but I am also using E46 brakes & proper ducting. I'd like to keep heat caused failures to a minimum, and rarely do more than 2-3 hot laps in a session as well. Time Trial car...

    I use FCP Euro for their lifetime replacement Brembo blank rotors that last half a season (5-6 events) before I replace them, using DTC60 pads.

  5. #5
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    Most of the cracks are micro, but the one near the glare in the picture goes to the edge and across the width of the rotor, and I could catch it with my fingernail. I should have mentioned that 6 of the 8 days were running with Chin at VIR and Watkins Glen, so quite a bit of track time.

    I only have the stock ducting that channels air into the wheel well, not proper ducting to the hat. Didn't think I needed it, as I haven't had a brake fade issue.


    IMG_1574.jpg

  6. #6
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    My one 'controlled' experiment with brake ducting is, it didn't matter. Friends (instructor/fast) 135i ran a half season with 1 duct installed, the other removed. No noticeable difference in rotor or pad lifetime, no degradation in braking. I'm just not sure the standard way of adding brake ducting to these cars do much good. I know others have different experience, but there are so many variables.

  7. #7
    joenationwide's Avatar
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    I ran brake ducts for years and always had issues cracking rotors, especially the drivers front (had the most corner weight).
    Once I completely blocked off my brake ducting, I've now had rotors lasting at least twice as long.
    I go probably 10 weekends on my front rotors now, at least. I used to only get through 5 weekends before.

    I don't know why, its just working. I run OEM rotors and Hawk DTC-60 pads, with R comps.

  8. #8
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    Quote Originally Posted by joenationwide View Post
    I ran brake ducts for years and always had issues cracking rotors, especially the drivers front (had the most corner weight).
    Once I completely blocked off my brake ducting, I've now had rotors lasting at least twice as long.
    I go probably 10 weekends on my front rotors now, at least. I used to only get through 5 weekends before.

    I don't know why, its just working. I run OEM rotors and Hawk DTC-60 pads, with R comps.
    I'd wager it's track specific, and you were over-cooling the rotors more often than not, leading to higher wear and cracking. WAG here though.

    There's only one local track that I really feel I need ducting on (Laguna), so my plan is to just disconnect the hoses or block off the vents for events at other tracks.
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  9. #9
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    ^Makes sense.

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    Typically I would replace my e36 m3 rotors after full season (approximately 5 2.5 day weekends). This was running aggressive pad compounds, and cheap chinese knockoff rotors from rockauto. Just another data point. Also seemed to last a bit longer once cooling was implemented, but that is more anecdotal than anything. Always carried last seasons rotors as a spare set in case of a split mid-weekend.

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    I use Carbotech XP20s on the stock 328 brakes - I get about 4 race weekends and testing (call it 10 days) before I replace them. They are severely "micro cracked" but there's no displacement anywhere. It's mainly a case of, if that lets go, it's going to be bad.

    You'll get more air into the brake hoses if they're mounted inside the radiator opening, rather than the fog light holes.
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  12. #12
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    Quote Originally Posted by CoMZ302 View Post
    You'll get more air into the brake hoses if they're mounted inside the radiator opening, rather than the fog light holes.
    Interesting idea. I've never seen that set up before.
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  13. #13
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    Running Willwoods up front. Hawk HT10 pads. Have over 15000 track miles on these and have never cracked one. I even have the front ducts blocked off. That said I do use the cool down lap to actually cool down. After I get into the paddock I do roll my car a foot or so. My theory is that the pads act as insulation and hold heat in while the car is sitting there so your rotor is pulling itself apart from the two different rates of cooling. Changing the rotors in a few events as I am going to switch pads up front to Poly H from Wilwood.
    I have crack a rear rotor and the cracks form almost in a perfect out line to the rear pads. Was in a hurry to get home and drove the car right up on the trailer hot. The rears are also cheap rotors from a local parts house. I now teach my student to "roll" their cars after they get off the track to aid the rotors in cooling. Maybe I am nuts but I would rather BS in the paddock and anticipate my next run the loose a run/day or an event on something I think is totally preventable.
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  14. #14
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    Thanks for the input, Guys...sounds like I'm not too far off from guys running stock brakes. I'm not ready to invest in bigger brakes yet, so I think that cracking will be a fact of life. At $40-$50 a rotor, not a big deal to carry spares (I buy FCP too, just never get around to packing up and return them).

    I definitely haven't been rolling the car, and tend to cool down when the traffic in front of me is Rolling is good idea to try to see if it extends the life a bit, makes sense that it would balance the cooling a bit.

  15. #15
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    This is odd. I've got 27 hard sessions on my rotors and even more on my PFC08 pads (50+) and have 0 issues. I am running cheap blanks, PFC 08 pads which are supposed to not be easy on rotors, stock/rebuilt calipers with upgraded guide pins, and a full cooling setup. I don't even bother bringing spare rotors with me to the track because wear has been so minimal.

    I share my car with a friend who is a pointy end racer, so the car is not being babied.

    I will say this though, my car does not like super hard braking so we elongate braking zones.
    Last edited by tripitz; 06-08-2018 at 12:39 PM.

  16. #16
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    Odd at the rate, or odd that they cracked at all? Most of my track friends in different cars see this, esp ones running OEM brakes...but they are running at the same events. Watkins Glen and VIR are fast tracks...WGI is pretty hard on brakes, so maybe that has something to do with it?

  17. #17
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    Odd at the rate. I ran at WGI as well, including some 45min sessions. I don't think WGI is as hard on the brakes as VIR because the turns are pretty fast (possibly turn 1 being the hardest and the left hander after the carousel being the "hardest" on the brakes).

  18. #18
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    I guess my comment was based on the other circuits I've driven, like Pocono and Summit main...

    The only thing not stock about the brakes are the brass guide bushings I installed up front. I suppose it's possible I didn't lube them enough and they were dragging slightly...causing more heat to the rotors. The wheels spun freely before my last day at WGI, but after I came home and had a couple of commutes with the car, there was some slight dragging.

    Since the Rotors already had a fairly decent amount of microcracks before my last event, I don't think this contributed all that much.

  19. #19
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    A lot of variables go into this. Fortunately, for those of running stock rotors, they are incredibly cheap. Picked up a set of blanks for $80 delivered a few weeks ago. Compared to other cars I have tracked, I'm happy. I have ~50 sessions on my PFC 08s and they still have tons of life left as well. Fortunately running costs are low for this car.

  20. #20
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    You can get rotors from Advance or similar that come with a two year warranty. If you are cracking rotor versus not chewing them up I think it is either the cooling down procedure or the quality of the metal. No free lunch. I run mostly VIR and CMP. CMP is worse than VIR on brakes and the fronts are still holding out fine. HT10 pads all the way around. Dont know what the PF replacement is for the 01 compound but that was the best for rotor life that I have run. Went to Hawk for $ and they were for sale where I was tracking.
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  21. #21
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    I totally agree about the cheap running costs...I wasn't concerned, as much as curious about other's experience.

    Thanks Guys!

  22. #22
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    Knew what you meant. Just for the benefit of the dialog. I have run cheap Centric blanks in the back and they wore pretty well and were very cost efficient. Always a balance between function and what we want to spend. That is why I think the cooling is so important after a session. Extra couple of minutes save extra couple of $$
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  23. #23
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    My StopTech slotted rotors lasted 12 track days before both of the fronts cracked.

    9 of those track days were without ducting.





    No idea what caused it, but they both seemed to have failed at the same time.

  24. #24
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    I think its not the ducting but rather you come in hot and the rotor has not cooled enough. Here is where the fun starts. The pads now act as insulation and the rest of the rotor is cooling at a different rate. If the temp was high enough the rotor just pulls itself apart. I am running the non M big brake kit from Massive and my ducts are taped shut and have not cracked a front ever. When I did do it to the rears the crack was almost a perfect trace of the pads. If yours cracked while running you should feel that but if not I would think it is the cooling cycle where you get the most damage.
    ME:"I want to make my car faster and lighter"
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  25. #25
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    I definitely prefer chewing up rotors than pads. Pads are expensive, especially PFC pads.

    On another note, I am using the BW brass/solid guide pin bushings. I just took the fronts out after an event in the rain and I am not happy with what I am seeing. They were incredibly dirty and showed uneven wear on the pins. This may turn into a redo after every event exercise. Anyone else use them and have a similar experience? Any decent alternatives besides going back to stock, which I do not like?

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