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      05-19-2011, 02:45 PM   #23
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Quote:
Originally Posted by aus View Post
Makes sense, but OP said he wasn't braking hard enough, per his instructor.
I would be very suprised at that looking at the heat checking on the rotors as that only happens with high heat.
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      05-19-2011, 02:51 PM   #24
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Who did you speak with at PFC? That is a very odd response from them on several fronts. They don't usually give out parts, they usually like to analyze, they usually are very fond of technical discussions, and almost nothing at PFC happens that easily. Also, I was not aware that PFC makes an 06 pad for that car - where do you get those? Not a critical point.

The explanation I have, after years of manufacturing failed parts on track myself, is that your picture shows a failure that I feel comfortable started at the edge of the ear on the rotor. The most brutal force in a braking system is the ABS - when a driver rides the ABS like we are taught in drivers ed, it hammers the components. In a race situation with more torque and bite and force applied via speed, this is extreme. Think of an air impact gun which is successful at destroying the bond of a rusted bolt by hammering it repeatedly or an air hammer - same action.

So in a PFC DD rotor, or any eared floating rotor, riding the ABS causes this hammering effect and will induce stress that results in fracture - if the PFC guy said "yeah, that happens" then this was the correct wording. And as you found out, when there is a vibration in any rotor, assuming it is fine is not the good path - glad you avoided damage, but you have got to listen to what a car is telling you on track. I learned this on an E36 M3 with stock rotors that shattered a front and luckily I was able to keep it out of the wall where it happened - and I have since applied my learning to multiple cars as rotors have failed both as a passenger and driver and have managed to avoid complete failure in the situations.

If you bought it from us and need additional info or support, email me or our guys and they can handle it. I don't personally feel that this is a widespread issue; I see cracked rotors every track weekend of some brand or another - that is what happens. We race on a very similar Direct Drive in Grand-AM with a 3700# car and we also use ABS and we haven't had the issue. I would say in general as drivers we can all learn though, no matter what brands we are using, that riding the ABS is not a good technique, beyond the potential for added stress and failures it induces. Looking at data, it just isn't as fast.
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      05-19-2011, 06:36 PM   #25
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Quote:
Originally Posted by ShadeD1 View Post
No idea how ABS would contribute. I try to threshold brake and my major correction from instructors is I'm not aggressive enough on the brakes.
ShadeD1, please elaborate on what you mean by "threshold". Do you trigger ABS on the track all the time? Or do you mean that you brake just enough before ABS kicks in?
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      05-19-2011, 07:45 PM   #26
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I try not to engage the ABS at all, and am 90% successful.

Quote:
Originally Posted by rldzhao View Post
ShadeD1, please elaborate on what you mean by "threshold". Do you trigger ABS on the track all the time? Or do you mean that you brake just enough before ABS kicks in?
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      05-20-2011, 07:51 PM   #27
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I assume this is a "street" rotor not meant for repeated track use (since its cross-drilled) ... but that doesnt excuse this fail along with James Clay's ABS excuse. People with e9xm3 run the OE rotor on the track with track pads and no cooling without this kind of catastrophic rotor failure.

I say its a poor quality street version replacement rotor.
Especially since BW runs their other rotor on their 3700# ABS'd e92m3 with no issues.
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      05-20-2011, 08:12 PM   #28
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It is not marketed as a street/track rotor. This is supposed to be a full on race rotor, afaik
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      05-20-2011, 09:33 PM   #29
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I learned something today.

I frequently check my rotors. I have the E46 M3 DD rotors on my 330. There are a bunch of tiny surface cracks which I've read are from the expansion of the rotor under heat.

I do carefully check the rotor for cracks which extend to the edge and where it mounts to the hat before and after I go to the track.
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      05-20-2011, 11:32 PM   #30
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Quote:
Originally Posted by ShadeD1 View Post
It is not marketed as a street/track rotor. This is supposed to be a full on race rotor, afaik
No such thing - no one sells (or should sell), or should buy for that matter - cross-drilled rotors for "full race" applications
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      05-21-2011, 06:39 AM   #31
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Quote:
Originally Posted by mastek View Post
No such thing - no one sells (or should sell), or should buy for that matter - cross-drilled rotors for "full race" applications
These rotors are not drilled.
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      05-21-2011, 12:02 PM   #32
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any updates? Most be a defective rotor?
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      05-23-2011, 12:17 AM   #33
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Quote:
Originally Posted by Gearhead999s View Post
The pulsing of the ABS will contribute to more heat in the brakes as you will tend to operate more at the threshold of maximum brake force than manually modulating the brake force without ABS.
Um, what the hell are you talking about?

Geez, I swear, I couldn't make this stuff up even if I tried.
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      05-23-2011, 12:22 AM   #34
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Quote:
Originally Posted by bigjae1976 View Post
I learned something today.

I frequently check my rotors. I have the E46 M3 DD rotors on my 330. There are a bunch of tiny surface cracks which I've read are from the expansion of the rotor under heat.

I do carefully check the rotor for cracks which extend to the edge and where it mounts to the hat before and after I go to the track.
First off, remember that these are different rotors than stock. The floating BMW factory rotors float on pins, not ears like this, and the failure mode would look very differently.

It's "normal" to have small surface cracks emanating from the holes in a drilled rotor, but if you ever have cracks all the way through the rotor, stop use of them immediately. Sometimes it's hard to see, but try shining a flashlight through the vents.

Definitely for those of you running non stock rotors, checking the areas that James mentioned is critical. Any cracks in those areas should be time to shitcan the rotor.

Also, what I hate about tracking a street car is that I almost inevitably get judder in my pedal from running a different street compound... makes it hard to notice a new vibration, but if you do, it's definitely time to pull off and closely inspect things.

I don't think you're going to see a stock rotor fail in the same way, although people have cracked stock rotors before...
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      05-23-2011, 04:52 AM   #35
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Quote:
Originally Posted by kitw View Post
First off, remember that these are different rotors than stock. The floating BMW factory rotors float on pins, not ears like this, and the failure mode would look very differently.

It's "normal" to have small surface cracks emanating from the holes in a drilled rotor, but if you ever have cracks all the way through the rotor, stop use of them immediately. Sometimes it's hard to see, but try shining a flashlight through the vents.
I understand the difference and I know surface cracks are normal as a result of heat cycling the rotors. But I'm not sure where all this discussion about cracks and holes (that's what she said) is coming from?

The PFC DD rotors are dimpled, not drilled. So the rotors are not drilled through so you can not see any cracks unless you look down the edges through the vanes. Which at that point, I'm not sure you'll be able to see anything.

IIRC, PFC's directions specifically caution against cracks extending to the mounting ears where the straps clamp the rotor to the hat.

So I'm not sure why you would bring up the OEM floating rotors???
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      05-23-2011, 07:51 AM   #36
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Quote:
Originally Posted by kitw View Post
Um, what the hell are you talking about?

Geez, I swear, I couldn't make this stuff up even if I tried.
`

Pretty simple.If drivers have a car with ABS they will use the brakes harder as it is much easier to get to the maximum threshold of traction without fear of lockup which in turn will create more heat from higher forces in the brake system.This is especially true where you have a lot of trailbraking where the inside of the car is unloaded for fairly long periods like corner 4 at Mt Tremblant.An ABS car in that situation will allow you to brake a lot later without the fear of locking up the inside tires and still braking harder than the other cars without ABS.
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      05-23-2011, 08:11 AM   #37
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Extra heat isn't really the issue with ABS, it's the shock load/impulse from rapidly applying and releasing brake pressure as the ABS system does its thing.

ABS isn't a speed tool so much as a tire saving and "code brown" avoidance tool. Using it to threshold brake is slower in most cases like James said. If ABS is engaging, you have, by definition, exceeded the threshold
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      05-23-2011, 09:34 AM   #38
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Quote:
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Extra heat isn't really the issue with ABS, it's the shock load/impulse from rapidly applying and releasing brake pressure as the ABS system does its thing.

ABS isn't a speed tool so much as a tire saving and "code brown" avoidance tool. Using it to threshold brake is slower in most cases like James said. If ABS is engaging, you have, by definition, exceeded the threshold
On a smooth track with standard type corners I will agree that getting into the ABS is a bad idea for fast times and shock loading issues.On a stock type suspended car with lots of weight transfer ABS will allow you to stay on the brakes without having to release brake pressure on the less unloaded inside tires to avoid locking them up and flat spotting tires which is faster in my experiance at the tracks that I have run at which are usually rough from our winters.On a stiffly sprung well damped suspension the ABS is probally a hindrance more than a useful driver aid but my stock M3 is far from being stiffly sprung!
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      05-23-2011, 11:03 AM   #39
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see this all the time, when in doubt switch them out
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      05-23-2011, 11:43 AM   #40
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Quote:
Originally Posted by Richbot View Post
Extra heat isn't really the issue with ABS, it's the shock load/impulse from rapidly applying and releasing brake pressure as the ABS system does its thing.

ABS isn't a speed tool so much as a tire saving and "code brown" avoidance tool. Using it to threshold brake is slower in most cases like James said. If ABS is engaging, you have, by definition, exceeded the threshold
Agreed. I've never had an instructor in 10 years instruct me to intentially/routinely use ABS. I've always thought if ABS is engaging in a big way - I'm too fast for where I want to start my turn-in. I've had it occassionally to trigger but not consistently.

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      05-23-2011, 11:54 AM   #41
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Quote:
Originally Posted by Gearhead999s View Post
`

Pretty simple.If drivers have a car with ABS they will use the brakes harder as it is much easier to get to the maximum threshold of traction without fear of lockup which in turn will create more heat from higher forces in the brake system.
Ok, this isn't the case.

Proper threshold braking with and without ABS do NOT create more heat. The danger of ABS is the hammering of a hot rotor.

Quote:
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`
This is especially true where you have a lot of trailbraking where the inside of the car is unloaded for fairly long periods like corner 4 at Mt Tremblant.An ABS car in that situation will allow you to brake a lot later without the fear of locking up the inside tires and still braking harder than the other cars without ABS.
I know the advantages of ABS, but the danger is not additional heat.

If you are talking about using the brakes more, then yes, you're right, using the brakes more does create more heat. It has nothing to do, specifically with the threshold of ABS
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      05-23-2011, 11:59 AM   #42
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Quote:
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Ok, this isn't the case.



If you are talking about using the brakes more, then yes, you're right, using the brakes more does create more heat. It has nothing to do, specifically with the threshold of ABS
Yes that is what I meant as maybe I did not state that very clearly.ABS does not create more braking force.
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      05-24-2011, 11:05 AM   #43
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Holy Crap!! I've got the same rotors!! Not tracking them any more though.
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      05-24-2011, 12:15 PM   #44
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Point is still being missed a little here by a few folks.
  • It is the hammering of the ABS causing the issue, as stated above
  • The rotor pictured got to 1600-1700 degrees to exhibit some of the characteristics in the pics - hammering a hot rotor = worse
  • This situation overstresses any type of rotor, but failure mode on a stock rotor will be different
  • Getting 20-30 track days out of a rotor, PFC or not isn't by any means out of the question - you just can't pound it like the pictured rotor, no matter what it is
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