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      01-28-2011, 01:37 AM   #1
VMZ432
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Total brake loss at 200kph plus! (Vid)

Closest I've come to losing my girl! I had total brake failure at the end of the straight on Wednesday at a local track. Foot to the floor, pumping.... nothing..... please come back please come back..... nope.... come on you b*stard!.... nothing..... oohh shit....

You can see the Civic bust out onto the straight much faster than I was expecting (36secs in vid, found out later he is supercharged and track only), and I should come nowhere near him into the first corner he is so far ahead. I should have started braking between the 1st and 2nd brake markers (58sec), but with nothing there I had to try to get around the Civic not knowing how hard he could brake. Once he was out of the way I still had get over some potholes, and then get the car turned through the gate. Possibly if I had coilovers (coming soon) I wouldn't have had to worry about the potholes so much and could have turned slightly earlier and not had to be so aggressive.

Somehow I had enough traction to get the car too far to the right, and had to correct to the left. But that helped shed some speed so I guess that worked out okay. I tell you what though, sliding through a gate out of control at that speed was pretty damn exciting!!!



First pic below is the aftermath. When I got back to the pits my front left brake was on fire and needed extinguishing, the liquid on the ground is what little brake fluid was left in the system. I think what happened is the pads and caliper over heated so badly that the seal in the brake line melted and started spewing fluid. I'll know more next week.

But don't worry these Stoptech's arrived this morning and go on next week. Combined with CL endurance pads I don't think this will be happening again. Period.

Not so sure about my instinct to go off track and take my chances with the gate rather than use a brother to slow down though. The safe thing to do might have been to clean him up. Still, it worked out okay.... me and my Z4 have one less life up our sleeve, that's for sure.
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      01-28-2011, 02:12 AM   #2
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Total brake loss at 200kph plus! (Vid)

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2006 IBlue BMW Z4 MC - ESS VT2-525 Supercharged, JRZ RS1 suspension (500#F, 600#R) with Vorshlag plates, ST Trophy BBK with CL R6E pads, KKS gated exhaust, TMS sway bars, RE rear camber arms, VT engine mounts, Recaro Pole Position (driver), APR GT wing, Street: Volk G2s and Potenza, Track: Volk TE37SLs and BFG R1s.
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      01-28-2011, 03:45 AM   #3
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Holy shitballs dude. Glad you're fine. That could have gone very very wrong. You are a very lucky guy!

How many laps did you go without letting your brakes cool?
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      01-28-2011, 04:37 AM   #4
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some mad skillz you have there mate !!!

might want to consider using a high temp brake fluid... I'm using Motul RBF600 for my track days.
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      01-28-2011, 04:49 AM   #5
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That was scary! Good to see that you're OK!

Update the thread once you know what actually went wrong. Were your brakes completely stock?

edit: just noticed from your signature that you have stainless steel brake lines, other than that?
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      01-28-2011, 07:33 AM   #6
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You are extremely fortunate in that there was an open gate you could go through. Glad you are OK. I experienced something similar at Watkins Glen in an E92 M3 two years ago after too many hot laps with the stock system + fluid + HT10 pads + SS lines. I was fortunate in that I ended up in a gravel trap.

I tracked the Z4M only twice, and was more careful with it, but I still saw similar issues with overheating brakes if you push it in a prolonged manner. Of course, it doesn't help that you've got a supercharger on yours.

I don't know if your brake system was completely stock, but I assume you had track pads and fluid in there?

I made several posts reporting rotor temperatures and saying be careful with the stock brakes, but got several responses saying the stock system is fine (not speaking to the OP here).

(Also, please don't start the "just don't overuse the brakes" line because it is a bogus argument for the most part; the faster you lap a track, the more heat you put into your brakes because you approach the braking zones at higher speeds and E_k=0.5*m*v^2.)

No, the stock system is absolutely not fine if you push the car in a prolonged manner--even if you have track pads and fluid. Be careful out there. If you are not sure about what's happening to your brakes, at least measure temperatures with an IR gun at the paddock when you come in. If you are seeing anything above 550C at the paddock, that is reason for concern and you should back off...

Something similar happened at Spa to a pro driver in a E92 M3 here:

http://www.m3post.com/forums/showthr...+brake+failure
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      01-28-2011, 09:15 AM   #7
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I'd say that counts for 2 or 3 lives, not just one. Had there not been an open gate - don't even want to think about it. That did not look at all like a very safe situation with regards to there being totally inadequate runoff at the end of a straight. .
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      01-28-2011, 10:10 AM   #8
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Quote:
Originally Posted by onebluemcm View Post
I'd say that counts for 2 or 3 lives, not just one. Had there not been an open gate - don't even want to think about it. That did not look at all like a very safe situation with regards to there being totally inadequate runoff at the end of a straight. .
What's ironic is that the car in your avatar had a similiar braking problem during a race and did a number of end-over-ends over a pretty great distance.
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      01-28-2011, 11:25 AM   #9
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nice save!
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      01-28-2011, 12:03 PM   #10
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Quote:
Originally Posted by VMZ432 View Post
Closest I've come to losing my girl! I had total brake failure at the end of the straight on Wednesday at a local track. Foot to the floor, pumping.... nothing..... please come back please come back..... nope.... come on you b*stard!.... nothing..... oohh shit....

When I got back to the pits my front left brake was on fire and needed extinguishing, the liquid on the ground is what little brake fluid was left in the system. I think what happened is the pads and caliper over heated so badly that the seal in the brake line melted and started spewing fluid. I'll know more next week.
I'm guessing it will turn out your brake line failed, due to road debris or something else cutting a slice out of it. I've also seen them fail because someone removed a caliper, then reinstalled with the line twisted the wrong way. I'm sure that's NOT what happened here, right? ;-)

You are very lucky, mixed in with some driving talent. Glad you managed to bring it safely to a stop! Would be interested to hear what the post-mortum determines was the cause. And congrats on the Trophy brakes. I've got them on my Corvette and love them!
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      01-28-2011, 12:07 PM   #11
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Your instinct was perfect. Many folks just can't handle that Oh Shiz moment and keep reacting.

Well played !!
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      01-28-2011, 01:18 PM   #12
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Op let us know what happened when you get the brakes off. I'm surprised there were no signs leading up to this. You would have had to have some serious fade to "melt the seals".


Quote:
Originally Posted by lucid View Post
I made several posts reporting rotor temperatures and saying be careful with the stock brakes, but got several responses saying the stock system is fine (not speaking to the OP here).

(Also, please don't start the "just don't overuse the brakes" line because it is a bogus argument for the most part; the faster you lap a track, the more heat you put into your brakes because you approach the braking zones at higher speeds and E_k=0.5*m*v^2.)

No, the stock system is absolutely not fine if you push the car in a prolonged manner--even if you have track pads and fluid. Be careful out there.
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.
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      01-28-2011, 01:58 PM   #13
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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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      01-28-2011, 04:55 PM   #14
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      01-28-2011, 06:18 PM   #15
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My experience is that the stock setup with upgraded pads and and fluid is just fine for continuous 120mph-40mph hard braking on a very technical track during thirty-minute sessions. (Pad suggestion thanks to Mr. Dave Zeckhausen)

One other possible contribution to this is that, perhaps, the OP didn't have enough pad-thickness for the additional braking that was needed as a result of the addition of the supercharger (higher speed = harder braking). Brake pads serve as both a friction surface as well as heat insulator between the disc and the caliper. Not enough insulator means more heat entering the system.
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      01-29-2011, 08:40 AM   #16
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Glad to see you're fine after.

Seems very strange to me if you didn't have major signs leading up to that. Especially after a long high speed straight where it seems you would have had some cooling.

Seems more possible to me like was said above a line failed.
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      01-29-2011, 10:10 AM   #17
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Quote:
Originally Posted by jragan View Post
My experience is that the stock setup with upgraded pads and and fluid is just fine for continuous 120mph-40mph hard braking on a very technical track during thirty-minute sessions. (Pad suggestion thanks to Mr. Dave Zeckhausen)
Things will be different when you get faster, go to different tracks which are harder on your brakes, and switch to r-compounds. I strongly suggest that you don't assume things are fine because there is a chance you'll find out the wrong way that they are not when things change.
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      01-29-2011, 12:11 PM   #18
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Quote:
Originally Posted by lucid View Post
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.
Your e30 M3 doesn't weigh anything that's why yop can continually beat on it. You probably have forced air cooling as well. The stock "brake duct" isn't very effective. And if you overheated your stock brakes in 3 laps... I have nothing to say to you.
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      01-29-2011, 01:04 PM   #19
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Reflexes on the OP were on point.....well played. lucky for you there was opening.....very lucky
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      01-29-2011, 01:04 PM   #20
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Quote:
Originally Posted by O-cha View Post
Your e30 M3 doesn't weigh anything that's why yop can continually beat on it. You probably have forced air cooling as well. The stock "brake duct" isn't very effective. And if you overheated your stock brakes in 3 laps... I have nothing to say to you.
If you read the post you quoted in detail, you'll see that I mentioned my E30 M3 has ducting and weighs less than a Z4M (~2500lbs without driver). It is slightly faster than the bone stock Z4M on a tight course. It does have smaller rotors, but that is not a huge consideration for the overall energy balance in prolonged use.

Yes, the Z4M brake vents on the bumper are not very effective (although I did not unblock them completely), and that is pretty much my point.

I wrote "I began" to overheat the front rotors after 3.5 hot laps. Specifically, start at ambient temp, end >500C at paddock without cool down lap after time trial. You can see where that would go if I were to put in 3-5 more hot laps.

Paddock rotor temp was ~600C after 20 minutes in a regular session (not all hot laps) and pads were smoking when I came in. No fade or failure, but if I put 3-5 hot laps on top of that, something could give. (Keep in mind on track peak temperatures are higher than these numbers).
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      01-29-2011, 01:16 PM   #21
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im also gonna do a complete break overhaul with TMS im gonna stay stock though and upgrade the lines and fluid thats it
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      01-30-2011, 10:20 AM   #22
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Quote:
Originally Posted by lucid View Post
If you read the post you quoted in detail, you'll see that I mentioned my E30 M3 has ducting and weighs less than a Z4M (~2500lbs without driver). It is slightly faster than the bone stock Z4M on a tight course. It does have smaller rotors, but that is not a huge consideration for the overall energy balance in prolonged use.

Yes, the Z4M brake vents on the bumper are not very effective (although I did not unblock them completely), and that is pretty much my point.

I wrote "I began" to overheat the front rotors after 3.5 hot laps. Specifically, start at ambient temp, end >500C at paddock without cool down lap after time trial. You can see where that would go if I were to put in 3-5 more hot laps.

Paddock rotor temp was ~600C after 20 minutes in a regular session (not all hot laps) and pads were smoking when I came in. No fade or failure, but if I put 3-5 hot laps on top of that, something could give. (Keep in mind on track peak temperatures are higher than these numbers).
Brake less, it's just that simple. System has it's capacity. It's possible for a race car to be able to use their brakes freely (not even all of them), not going to happen easily in a street car. Even once the OP has his stoptechs on they will have their capacity, and it's still very achievable for a 3,200 lb car on rcomps.

Not many people install forced brake cooling in street cars.
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