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      06-28-2009, 01:31 AM   #1
Montoya
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Trail braking, rear brake bias?

I tend to trail brake deep into a turn and I have noticed that the rear brakes tend to lock-up easily. Of course this is most noticeable when downshifting simultaneously. It really wrecks smooth corner entry for me when the back end starts to step out. My old E46 M3 felt more planted in this respect.

Has anyone else noticed this and is it possible to adjust the brake bias?
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      06-28-2009, 08:16 AM   #2
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Quote:
Originally Posted by Montoya View Post
I tend to trail brake deep into a turn and I have noticed that the rear brakes tend to lock-up easily. Of course this is most noticeable when downshifting simultaneously. It really wrecks smooth corner entry for me when the back end starts to step out. My old E46 M3 felt more planted in this respect.

Has anyone else noticed this and is it possible to adjust the brake bias?
Nope, I finish all my braking before I enter into the turn. I do not recommend trail braking, it'll bite you in the ass one of these days. Remember, slow in fast out...

Here's my little discussion on the topic in another thread:
http://www.m3post.com/forums/showpos...6&postcount=80
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      06-28-2009, 08:34 AM   #3
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I suspect your issue might really be rev matching rather than trail braking. ABS should prevent a noticable lock-up under threshold breaking.
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      06-28-2009, 08:44 AM   #4
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Originally Posted by lucid View Post
I suspect your issue might really be rev matching rather than trail braking. ABS should prevent a noticable lock-up under threshold breaking.
He has the DCT so rev matching should not be an issue. No amount of technology will save the car if the driver puts it in an unrecoverable condition. 99.99999% of the car crashes I've witness was due to braking in the corners, the Ring is more unforgiving than other tracks but it still illustrates my point. Better to not brake in the turn. Finish your braking, be on the gas by the time you hit the apex. You'll be flying out of the corner and the acceleration coming out of the turn far out weighs the time you might have saved by diving into the corner.
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      06-28-2009, 09:07 AM   #5
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Trail braking is just another driving skill, I don't find it so dangerous. Some corners almost require it for a fast time, slower, decreasing radius corners come to mind. I can't imagine being a more than a mediocre driver without knowing how to rotate the car under braking. We're not talking about left foot braking even.

I find the M3 trail brakes easily, more predictable than my Cayman S (which has Pagid blacks in back to give more rear bias). I ran Carbotech XP12s on the M3 yesterday at the track, they're kinda grabby which concerned me but they were fine and not as tough to modulate in trail braking as I thought they would be.

Neither car has much rear brake bias, typical of all cars, BMW doesn't want you spinning it off the highway in a rainstorm.

Slow in, fast out and brake in a straight line is harped on at DEs for safety. It allows you to better set corner entry speed which is where most beginners screw up. A quicker lap is fast in, faster out.
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      06-28-2009, 09:23 AM   #6
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Quote:
Originally Posted by armyav8tor View Post
He has the DCT so rev matching should not be an issue. No amount of technology will save the car if the driver puts it in an unrecoverable condition. 99.99999% of the car crashes I've witness was due to braking in the corners, the Ring is more unforgiving than other tracks but it still illustrates my point. Better to not brake in the turn. Finish your braking, be on the gas by the time you hit the apex. You'll be flying out of the corner and the acceleration coming out of the turn far out weighs the time you might have saved by diving into the corner.
ABS keeps wheels from locking up in a noticable manner due to braking. Anything else that you do to the car while turning in which might exceed the traction it has and gets it if off the track is a seperate consideration. (Too much steering input or a poor downshift will cause loss of traction as well; basic traction circle stuff). The OP is complaining about his rear wheels locking up due to braking. ABS can't keep your car on the track, but it will keep you from applying more brake pressure than the tires can deal with as long as you are not spinning. Who knows what happens exactly in a spin since you have all sorts of unusual lateral loads, etc.

I haven't driven a DCT car on the track, so I don't know how the different modes behave while downshifting, and if it is possible to lock up the rears in certain modes.

As to how to go in and out of a corner, I think consolidated already answered that question.
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      06-28-2009, 09:33 AM   #7
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Quote:
Originally Posted by consolidated View Post
Trail braking is just another driving skill, I don't find it so dangerous. Some corners almost require it for a fast time, slower, decreasing radius corners come to mind. I can't imagine being a more than a mediocre driver without knowing how to rotate the car under braking. We're not talking about left foot braking even.

I find the M3 trail brakes easily, more predictable than my Cayman S (which has Pagid blacks in back to give more rear bias). I ran Carbotech XP12s on the M3 yesterday at the track, they're kinda grabby which concerned me but they were fine and not as tough to modulate in trail braking as I thought they would be.

Neither car has much rear brake bias, typical of all cars, BMW doesn't want you spinning it off the highway in a rainstorm.

Slow in, fast out and brake in a straight line is harped on at DEs for safety. It allows you to better set corner entry speed which is where most beginners screw up. A quicker lap is fast in, faster out.
I hear what you are saying. My track experience consist of one track so maybe when I go to one that benefits from trail braking, I'll use that technique. If you drive the Ring, I would recommend against it due to the undulations, different surfaces and altitude changes.

BTW, slow in fast out and fast in faster out is the same thing. slow + 1 = fast, fast +1 = faster. I've never been to DE, all my driving experience comes from experimenting different techniques on my own. I've never worn a helmet or gloves in a car, its going to be a different experience driving in the States with all the rules and such... hehe
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      06-28-2009, 10:22 AM   #8
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Originally Posted by armyav8tor View Post
I hear what you are saying. My track experience consist of one track so maybe when I go to one that benefits from trail braking, I'll use that technique. If you drive the Ring, I would recommend against it due to the undulations, different surfaces and altitude changes.

BTW, slow in fast out and fast in faster out is the same thing. slow + 1 = fast, fast +1 = faster. I've never been to DE, all my driving experience comes from experimenting different techniques on my own. I've never worn a helmet or gloves in a car, its going to be a different experience driving in the States with all the rules and such... hehe
You need to get yourself to a DE, it only takes one to set the hook. Then prepare to scorch your bank account, credit cards and kid's piggie banks.

The 'ring is fast, open track and with little margin for driver error, I agree not an ideal place to experiment or even learn basic performance driving skills. It's gotta be hard to just recall all those corners, much less try to push.
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      06-28-2009, 10:43 AM   #9
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Quote:
Originally Posted by Montoya View Post
I tend to trail brake deep into a turn and I have noticed that the rear brakes tend to lock-up easily. Of course this is most noticeable when downshifting simultaneously. It really wrecks smooth corner entry for me when the back end starts to step out. My old E46 M3 felt more planted in this respect.

Has anyone else noticed this and is it possible to adjust the brake bias?
I have not driven an M-DCT on track but in my previous E46 M3 with SMG and my wifes old GTI DSG it helped the smoothness quite a bit in both cars if you blipped under downshifts on track.In both cars the negative torque of the downshift if just left to the electronics affected the atitude of the car,I am not talking about the amount of throttle opening one would use on a manual car but just enought prevent negative torque at the wheels.I believe your issue is caused by the electronics not being aggresive enough in the this situation and depending on the corner I trail brake a lot.
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      06-28-2009, 11:07 AM   #10
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Quote:
Originally Posted by consolidated View Post
You need to get yourself to a DE, it only takes one to set the hook. Then prepare to scorch your bank account, credit cards and kid's piggie banks.

The 'ring is fast, open track and with little margin for driver error, I agree not an ideal place to experiment or even learn basic performance driving skills. It's gotta be hard to just recall all those corners, much less try to push.
I think you have to be signed off by a DE here for something like a NASA event before you can drive the track on your own, correct? I've seen plenty of crashes and is well aware of the costs, especially at the Ring where they charge you for everything. I did the track walk with RSR and the guide said they add new Armco barriers every year to the point where every section of the track is covered. He gave the example of the "7 sec ring king" where the guy crashed as soon as he entered through the gate at Breidscheid, in the youtube video there was no Armco there, well, there is now. Those Armco barriers are not cheap either.



I think I've held my own on the Ring, being that it is supposed to be the hardest track in the world. I've manage to come out of it without too much drama. I attribute most of that to my control touch, my better than average depth perception, and my "seat of the pants" flying (knowing when the tires are reaching their limit of traction, etc.), the stuff that has also made me a good pilot. I've memorized every corner of the track and the fastest lines in the dry and wet but I am by no means a serious racer, just out to have a good time and to test my abilities and courage. You need giant balls to drive the Ring fast on a public track day. But I do look forward to driving here and seeing what new skills I can pick up. I plan on hitting Road Atlanta think in October they have a NASA event?...
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      06-28-2009, 11:17 AM   #11
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That video is hilarious, "and we're at the 'Ring!"....crash. You knew it was coming since you could see all manner of stuff sitting on top of the dash, including a Snickers bar.

Your video looks great. What sort of times were you doing? Always been curious about what times a skilled tourist would put down.
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      06-28-2009, 11:42 AM   #12
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Quote:
Originally Posted by consolidated View Post
That video is hilarious, "and we're at the 'Ring!"....crash. You knew it was coming since you could see all manner of stuff sitting on top of the dash, including a Snickers bar.

Your video looks great. What sort of times were you doing? Always been curious about what times a skilled tourist would put down.
Yeah, what's funnier was that as soon as the guide mentioned the 7sec ring king, everyone knew what he was talking about.

I lap around 8:30 BTG usually, not working the tires and brakes too hard. I've managed to baby the PS2s enough for them to last >40 laps and put just over 12,000 miles on them, the brake is another story, warped them 2x (warp = uneven OEM pad material all over rotor causing undriveable jittering). The last Nurburgring weekend before moving back to the States, I was trying hard to get a sub 8 min lap on video but the tires (headless Michelin man) and brakes (had bad brake jitter all weekend, you can actually hear it in the videos) were on its last leg long before the weekend. I think I had a good shot a few times still but then traffic got in the way. In addition to dodging motorcyles and cars, you have to be prepared for oil spills and other crap on the track (hit a nice long oil spill on one of the fastest portion of the track that weekend, not fun). A 8:30 lap is comfortable, anything faster and you are putting yourself at greater risks. The Ring Taxi usually lap it in 8:30, but they are drifting through every corner so they are not exactly going for a fast time. A sub 8 min lap would be easy with our M3 on a closed circuit and Cup tires.
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      06-28-2009, 11:52 AM   #13
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as was said all downsaifting and heel toe should be done before trail braking.
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      06-28-2009, 01:21 PM   #14
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Quote:
Originally Posted by armyav8tor View Post
The last Nurburgring weekend before moving back to the States, I was trying hard to get a sub 8 min lap on video but the tires (headless Michelin man) and brakes (had bad brake jitter all weekend.....

I think I had a good shot a few times still but then traffic got in the way. A sub 8 min lap would be easy with our M3 on a closed circuit and Cup tires.
There are lots of people here who would love to see a sub 8 minute lap. No offense, but I have a feeling it's a lot harder than you think even on Cups.
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      06-28-2009, 01:59 PM   #15
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Originally Posted by consolidated View Post
There are lots of people here who would love to see a sub 8 minute lap. No offense, but I have a feeling it's a lot harder than you think even on Cups.
No offense taken, here's my take on it. I was within 15 sec of that goal in traffic and when the tires/brakes were still decent back in 08. In my last trip, the best I could do was 8:17 BTG with almost no traffic. Tires make a huge difference, the 8:05 full lap time done by Sport Auto were on Cup tires (I wonder if they were on stock pads). The final straight takes 20-25 sec to complete, so in theory, a BTG time of 7:40 is attainable under good conditions (ie. closed circuit). The M3 is so easy to drive, so neutral, that I believe I could get under 8 min without breaking a sweat if I had a clear track and better tires. Too bad I didn't listen to the wife and switch out the rotors and tires before the last trip or we might be watching a sub 8 min lap from me (I'm sure somebody will post one sooner or later, I've seen sub 8 min laps from CSLs). I was hoping they would last until I got back to the States but the car was undriveable after that weekend and I ended up changing them anyway.
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      06-28-2009, 06:27 PM   #16
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Not to take away from the subject here, but here is a sub 8 - although not a BMW

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      06-28-2009, 07:23 PM   #17
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Quote:
Originally Posted by sayemthree View Post
as was said all downsaifting and heel toe should be done before trail braking.
I cannot think of any tracks that I run on that there is not at least one corner where you trailbrake on a lap if you want to go quick.Trailbraking is a very important part of putting together a proper lap at any track that is more complex than 90 degree corners.
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      06-29-2009, 08:16 AM   #18
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Upon further review of the video of my friend following me, I see what might be trail braking. The corners in question are both the late entry corners, Aremberg and Bergwerk. Not so much at Aremberg (2:22) but Bergwerk (4:44)





Tell me what you think. With no formal driver training, I basically drive intuitively.
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      06-29-2009, 12:11 PM   #19
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Perhaps for most of us it is difficult to provide an opinion. I for one, not knowing the track, I have difficulty in judging where turn in should be in order to exit (track out) for the next track section. In some areas it looks like you are crowding the turn in, i.e. anticipating and beginning to move the car toward the turn, rather than waiting a nano sec then turn - but having said that, I don't know the turn so your line may be absolutely correct. You drive smoothly, which is 90 percent where you want to be, and you kept all four where they should have been.

As to your trail brake, sorry, but I simply could not tell.
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      06-29-2009, 09:18 PM   #20
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Quote:
Originally Posted by von_zoom View Post
Perhaps for most of us it is difficult to provide an opinion. I for one, not knowing the track, I have difficulty in judging where turn in should be in order to exit (track out) for the next track section. In some areas it looks like you are crowding the turn in, i.e. anticipating and beginning to move the car toward the turn, rather than waiting a nano sec then turn - but having said that, I don't know the turn so your line may be absolutely correct. You drive smoothly, which is 90 percent where you want to be, and you kept all four where they should have been.

As to your trail brake, sorry, but I simply could not tell.
vz
I have to agree with VZ says about the video,but what the heck is up with the shifts on the camera car?Have to chuckle at the kids carrying on just like it is normal Sunday drive or maybe it is for them
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      06-30-2009, 08:39 AM   #21
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Originally Posted by von_zoom View Post
Perhaps for most of us it is difficult to provide an opinion. I for one, not knowing the track, I have difficulty in judging where turn in should be in order to exit (track out) for the next track section. In some areas it looks like you are crowding the turn in, i.e. anticipating and beginning to move the car toward the turn, rather than waiting a nano sec then turn - but having said that, I don't know the turn so your line may be absolutely correct. You drive smoothly, which is 90 percent where you want to be, and you kept all four where they should have been.

As to your trail brake, sorry, but I simply could not tell.
vz
The lines are by the book except for Brunnchen where I like to go down past the red and whites because Brunnchen is the most popular viewing point and I like to give the audience false hope (that I lost the car and about to crash) so I've renamed those 2 corners "False hope 1" and "False hope 2". You can actually see me kick up so dirt in the video above.... hehe

Here's the wrong way to go into Brunnchen, this happens more often than you can imagine:


Here's my in car video:


Quote:
Originally Posted by Gearhead999s View Post
I have to agree with VZ says about the video,but what the heck is up with the shifts on the camera car?Have to chuckle at the kids carrying on just like it is normal Sunday drive or maybe it is for them
He might have rode the clutch a little (I can't even make an excuse up)... But yeah, that's how the Germans do it. Whole family goes down to the track for the weekend. You see vans, buses, trucks, etc... on the track. That is why it is so hard (risky) to get a fast lap in on a public track day.
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      06-30-2009, 08:52 AM   #22
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So many things go wrong in that crash video--apart from the crash itself. I wouldn't even come close to pushing the car on that track. There doesn't seem to be timely medical/emergency response. What if there was a fire or a broken neck? The cars behind the crash don't seem to know that there has been one are diving into that turn (relying on the public to act like flaggers is not a good idea). People pull off in the middle of the track right by the rolled over car--many risks there. Then of course there is the open passing driving itself with people around you who seem to know very little about performance driving. That's crazy. Rather, crazier than pushing your car on a properly operated race track on which drivers are supervised. I am crazy enough to do the latter but not the former. When you start attending HPDEs in the US, you will be in a less risky environment in which you can learn in a more structured manner. One can try to drive fast on his/her own and pick things up on the way, but there is nothing like trying on your own a little, picking up someone who is more experienced and having that person evaluate what you are doing. So much more effective. And keeps you from learning the wrong thing.
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