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05-19-2011, 02:45 PM | #23 |
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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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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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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, 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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05-21-2011, 06:39 AM | #31 |
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These rotors are not drilled.
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05-23-2011, 12:17 AM | #33 | |
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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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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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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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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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05-23-2011, 11:43 AM | #40 | |
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BC
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05-23-2011, 11:54 AM | #41 | ||
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Proper threshold braking with and without ABS do NOT create more heat. The danger of ABS is the hammering of a hot rotor. Quote:
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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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, 12:15 PM | #44 |
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Point is still being missed a little here by a few folks.
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