ABS Disengagement

[TIATO]

Threshhold braking on video

Heres one of my older videos which at the 5min 39sec mark shows me slowing my M Coupe down from 115mph for Watkins Glen turn 1.

May not be very obvious, but once the video hits 5:39, listen to the sound my brakes make, watch my hand on the steering wheel after I move my right arm to downshift. You will see my left hand moving the wheel.

For the M Coupe that was the Maximum non ABS braking point. I had transfered so much weight to the front of my car that the rear got so light it started fishtailing. My hand is moving the wheel to correct.

Bone Stock M Coupe on street tires with Performnce Friction PF97 Race Pads.

I find this video very entertaining for all the noises a car can make in turns and during braking.

Video is in .mov format, about 31mb and more than 8 minutes long.

Coupes At The Glen[/url]

[modifiede30]

Im of the opinion, that the more you can do without drivers assistance (ABS, DSC or whatever) the better a driver you will become and also develop a much better and consistent feel for a cars limits. Performance driving is always about feedback and feel. Drivers aids take that away.

I've never driven a car with DSC, but as for ABS, I've had it engage in the rain and it felt as though the car was simply coasting while the pedal was solid. A real strange experience - closing in on scary. I found through trial and error (in a safe environment) that the ABS eliminates the driver's "contact" with the car in terms of braking. There really is no feel left, which personally eliminates the whole point of track driving. If DSC approaches this in the least bit on a track, I'd be even more uncomfortable given the consequences of the car lightening up too much in a turn. The loss of "feel" would also be a drag.

One of the main reasons for posting this, and a point that has not yet been discussed is the consequences of spinning with ABS. Every instructor, either in the class-room or in the car, always warns that the ABS in a spin will not allow the car to predictably spin in the direction of you momentum, but rather, allows wheel movement which can throw the car in various directions. Since the ABS senses lockup (both feet in you know), the car will not continue in the direction of the momentum of the car. This can be very dangerous.

Anyway, glad this turned into a good thread. And don't imply that 34 is getting "older" (I'm 33 next month).

[UNHCLL]

One of the main reasons for posting this, and a point that has not yet been discussed is the consequences of spinning with ABS. Every instructor, either in the class-room or in the car, always warns that the ABS in a spin will not allow the car to predictably spin in the direction of you momentum, but rather, allows wheel movement which can throw the car in various directions. Since the ABS senses lockup (both feet in you know), the car will not continue in the direction of the momentum of the car. This can be very dangerous.

Anyway, glad this turned into a good thread. And don't imply that 34 is getting "older" (I'm 33 next month).

:oops: I thought TIATO was closer to the 45 age bracket for some reason.. My mistake. 33/34 is young. Besides age is just a number, I know some 70 year olds who can drive better than a LOT of people.

I echo the thoughts on this becoming a good convo! :up:

[modifiede30]

I know some 70 year olds who can drive better than a LOT of people.

Funny you say that. One of my recent instructors was about that age, and he still held the track time record at NHIS in an open wheeled category. Funny thing was that it wasn't set that long ago. :D

[TIATO]

.... allows wheel movement which can throw the car in various directions. Since the ABS senses lockup (both feet in you know), the car will not continue in the direction of the momentum of the car. This can be very dangerous.

I was going to write the same thing earlier, just didnt have the time then. ABS, with its tire slip (rotation while braking) allows for too many unpredictable variables vs non ABS cars.

[modifiede30]

Jordan, this might be a good thread to copy over to the Track/Auto-X section given the content.

[Charlie]

Jordan, this might be a good thread to copy over to the Track/Auto-X section given the content.

Done and done.

-Charlie

[Stu]

What sort of tips can you experienced instructors/track drivers give for novices that want to learn advanced techniques of braking? Threshhold braking?

Thanks.

[rwh11385]

Even newer systems.
To break it down to the parts of braking...(Ultra simplified)
Threshold Braking is the MAXIMUM pressure that can be applied to the brakes before lock-up occurs.
Once ABS kicks in, you have passed this optimal level, and the brakes are "cycling"
The cycling is very quick on newer cars, but for that split second, the brakes are still releasing pressure on the rotors and allowing more "slip"

This is overly exagerated on the E30 as it is an antiquiated system. The pause while pressure is released is long. Threshold will always stop you faster than full ABS Lock-up braking. Stressing this point is the essence of our Saftey Schools when teaching Panic Stops. Throw into the equation, turning, weight transfer, and the speed the mind must process that.... students can very quickly fall into the "Stomp the pedal and stand on it" mentality.

I don't have a working ABS. The previous owner had gotten one of the speed sensor's broken for some reason, and removed it, and now it doesn't work at all. Even though i'm used to using ABS, i've only locked up my wheels once - the first time.

I'm going to be taking Safety and Driving schools, and don't know how trusting i am of the antique ABS system E30's have, not to mention the costly repair of the ABS sensor that could be put towards better things -- like admission into the driving schools, or entry into autocrosses.

Do you think I ought not to replace it, Tiato, UNCHLL, modifiedE30 ?

thanks

[modifiede30]

I wouldn't. I'd spend it on other brake components, such as good rotors and pads before replacing the ABS. Steel lines would also be a good investment depending on your plans. However, if only street driving is in your future, it might be better to think about the ABS since not learning to threshold brake may be problematic.

[TIATO]

What sort of tips can you experienced instructors/track drivers give for novices that want to learn advanced techniques of braking? Threshhold braking?

Thanks.

Pedal feel is key to effective braking and modulation.

Lets start with what I consider the most important driver to car interface as far as braking is concerned- footwear. Appropriate footwear make a huge difference in pedal feel. Shoes with thin, solid rubber soles such as racing boots, Sperry docksiders, Piloti driving schoes, heck even wrestling shoes will allow you to feel the pedal and the subtle feedback a braking system will give.

Sneakers are a no no. To squishy and the pedal feel is virtually dampened by the foam.

While not neccesary other factors that improve pedal feel are stanless steel lines and a larger brake master cylinder. These however refine it.

The next thing would be to practice, first to get a general feel to it in a low stress situation, then progress to braking under the heat of the moment - track or autocross.

Another aspect is brake dicipline. You cant just stomp on the brakes. Brake actuation has to be fast and smooth. Brakes have to be squeezed with gentle authority.

Best way would be to brake hard enough to actuate ABS, then gradually back off pedal to a point where it feels like the brakes will lock up (but actually go into ABS) y. Note mentally what brakes nearing ABS (full non ABS ) feeli like. Note how much (by feel) you depress the brake pedal, note the sound the tires make, the dive or attitutude of the car.

Do it enough times where you can get a feel for how much and how hard to press the brake pedal. Once you get an aproximate feel, work on consistency.

Once you got consistency, work on at the limit brake modulation.

I prefer to practice this while decelerating from high speeds. Gives me more pedal time. I also do this exercise in a variety of different cars. I also do thi at slow speeds.

A frim brake pedal makes this exercise and actual real world application significantly easier.

[modifiede30]

What sort of tips can you experienced instructors/track drivers give for novices that want to learn advanced techniques of braking? Threshhold braking?

An activity that really helped me was to find an empty parking lot during a rainy day, and get going up to about 35-40mph, and brake to a complete stop. Continue to do this using greater pedal pressure until you reach the point where the ABS kicks in. Once you've experienced the ABS a bit, continue the exercise but back out of the brakes each run until you no longer feel the ABS. The exercise will give you a sense for where it kicks in and how if feels. It also alows you to recognize the point just before it initiates. At the track you'll be going a bit faster but the feel is very similar, just a bit more stressed.

As mentioned earlier in the thread, stomping on the brakes is not good, and tends to unsettle the car, making for a very UN-SMOOTH ride. As you've probably heard, smooth is godliness. This exercise will teach you to squeez the brakes rather than stomp the brakes. In order to do this, give yourself enough room in the parking lot so that you can test the various pressures necessary to engage ABS. You'll find over time that you'll be stopping the car just as quickly, and with some practice, more quickly, without ever initiating the ABS. Use cones as a way to measure your distance and to obtain a point of reference.

Be safe, and have someone come and join you. Given the other posts I've seen of yours your dad would be a good person to help. I know the name and I'd welcome someone like that in my passenger seat.

[UNHCLL]

An activity that really helped me was to find an empty parking lot during a rainy day, and get going up to about 35-40mph, and brake to a complete stop. Continue to do this using greater pedal pressure until you reach the point where the ABS kicks in. Once you've experienced the ABS a bit, continue the exercise but back out of the brakes each run until you no longer feel the ABS. The exercise will give you a sense for where it kicks in and how if feels. It also alows you to recognize the point just before it initiates. At the track you'll be going a bit faster but the feel is very similar, just a bit more stressed.

This works well but one tip:
In order to combat some severe frustration with learning the ABS curve, try to find a parking lot that has little to no lines for parking spots. This get more slick than pavement when wet, so if you're crossing those often ABS will engage a lot sooner, and it defeats the purpose.

Another thing I teach is threshold braking while turning. Its different than straight line threshold braking. The inside wheel is more prone to lock-up as it has less weight on it.
Master straight line, then work into corner. 30-35 is a good bracket to start with for speed.

Here is how I instruct:
1) Tell all students to line up and when I signal get on the gas and accelerate towards me (get to +/-30).
First time through, SLAM on the brakes, full out panic stop to save jimmy who's chasing his ball.
I mark this stop point with full ABS actuation.

Then I tell them to go back through and stop BEFORE that point, without using ABS.
Takes a couple tries, but they get the hang of it.

Having some cones you can lay down or stand up to mark a "Brake point" is also VERY helpful. This gives you a semi-benchmark to gauge your stopping distances from each time.

[Sean]

My mom's 00' 528i Touring has DSC...I hate it. During the winter, if I tried to accelerate, the tires would spin naturally - with DSC enabled, my power would be cut and it would take twice as long to asselerate as it would with it off (even with tire spin).

My car has ABS, still works, and I've hit it a few times in teh rain, but that's about it.

A very informative thread, nonetheless.

[OreoGaborio]

i'm glad new live was breathed into this thread... didn't catch it the first time around.... :up: :up: