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      01-28-2011, 12:58 PM   #13
lucid
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Drives: E30 M3; Expedition
Join Date: Apr 2007
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Quote:
Originally Posted by O-cha View Post
It is a matter of don't overuse the brakes though, stock system has its capacity, don't keep hammering on them after they have faded. That's what "being careful" is. Even A large BBK on track, in a full weight road car on Rcomps can easily be overused. You need one hell of a system to be able to just go continually drive as fast as possible without burning your brakes up.
I wrote monitor temperatures and "back off" when I said be careful. If your definition of being careful is back off when you experience fade, I completely disagree. That's not being careful (or being in control for that matter). That's saving the day.

And, I began to overheat the stock Z4M system just after 3.5 hot laps in a time trial on OEM tires, not after 45 minutes on r-compounds. That is how poorly that system is set up stock. Seems to be an issue with recent BMWs in general, especially M cars. P-cars seem to do much better with their OEM systems for instance.

There are fade proof brake systems--meaning the net energy flow into the system over the course of a lap is not positive. If it is positive, you'll eventually cook your brakes unless you back off. I can beat up on the brakes on my E30 M3 all I want, and nothing will happen until I run out of pad material, but that has proper ducting and obviously a lower hp/lb ratio.

The critical variable in sustained operation is not really the mass of the rotors, but their ability to transfer heat into the environment, which ultimately boils down to cooling and forced convection. If you can get that right, then you have a system that can be operated for much longer.

Also, although there are often signs, that's not always the case; it depends on the failure mode of the part that is failing. In my case, the HT10s self destructed. They literally physically fell apart as in pad material came off the plate, and they were doing fine until then. I kind of sensed an issue the turn before the one I went off, but it wasn't anything major. I spoke with 2 other people who experienced the exact same thing with that specific pad. The point is the pad wouldn't have failed if temperatures weren't that high, and when it failed, it self-destructed with almost no warning because it wasn't simply a matter of CoF gradually dropping off with rising temperatures which often results in significant warning.

Check out the thread I linked above re brake failure at Spa. One would figure a pro driver would be able to detect fade, right? He says there was none, and the failure was abrupt. So you can't always count on fade as the warning.

We don't know the specifics of what happened to the OP. My guess is that it is overheating related. Even if it isn't, I strongly suggest monitoring rotor temperatures as that is the most objective, safe, and proactive way of "managing" overheating issues. Of course, using temperature sensitive paint would be the best aproach there.
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Last edited by lucid; 01-28-2011 at 01:45 PM..
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