Pulling 'P' brake in emergency high speeds?

[singularity]

Had an unfortunate moment today and thought I'd share. I've had several dangerous situations of almost hitting an inappropriately parked car on a road or even a highway. To keep it brief, I was in a situation when I was accelerating at around 150 km/h and saw a parked car about 250 meters away.

The moment I realized it's parked I floored the pedal hoping my car would stop before the 'deadline'. ABS kicked in as soon as I started breaking and it felt to have significantly increased my braking distance, maneuvering was not an option as I didn't want to make unexpected moves on the road. When there was about 80 meters left (and heavy traffic on other lanes) I realized that my car won't come to a standstill when I expect it and I was damn sure I would hit the parked car - this is when I found a small opportunity gap on the left lane and 2-3 meters before hitting the parked car I dived to the left lane.

I was lucky a good fellow driver realized I would have to change lane or hit the car in front of me and gave me a chance to move to his lane. Needless to say I was very thankful to him. I drove to a quiet speedy road and for the first time tested the electronic handbrake AND full stop brake and it seemed to have shortened the ABS distance and planted the car very firmly.

Is the electronic handbrake designed to be used at high speed situations similar to mine today? Has anyone tested actual braking distances with Brake/Handbrake/Brake+Handbrake?

[Marcus Frost]

As someone who has both:

1.) Driven an ABS car without rear brakes (long story)
2.) Had extensive experience with traditional handbraking in performance driving

What you are implying makes no technical sense. Not only do rear brakes do relatively little work, especially in situations where the brake pedal is used firmly, the effective "locking" if the rear wheels defeats the purpose of ABS (anti-lock brakes). In essence, ABS systems are designed to modulate brake system pressure so that the wheels do not lock up. When wheels lock up they not only compromise braking distances, but they also introduce instability into the braking process.

So unless BMW built in a whole separate programming logic into their stability control program that takes into account the different dynamics of locked rear wheels, you are likely experiencing a placebo effect. In other words, hand braking does not reduce braking distances or enhance braking performance, it actually does the opposite.

Have you ever seen people hand brake in professional racing? Yes, you have, in rally and drifting - two forms of racing where the introduction of instability is actually necessary.

[singularity]

Originally Posted by Marcus Frost

Have you ever seen people hand brake in professional racing? Yes, you have, in rally and drifting - two forms of racing where the introduction of instability is actually necessary.

Hi and yes I have, I practice handbrake drifting on my M6 E63, in fact had a lot of it during snow slaloms. I don't know how handbrake engages in M5 F10 but when attempting to pull the same electronic P in snow to simulate a manual hand-brake with a turn, the car straightened itself and dug in coming to an immediate stop.

Maybe it's a placebo effect and my lack of knowledge, I guess my evaluation of acceleration dynamics and estimated braking distance is just horrible then, not that I had any control of today's situation but this isn't the first time I have issues with high speed braking in this car.

[Boss330]

Two points:

1: The electric handbrake on the BMW (or like on any other European car with electric handbrake) also acts as an emergency brake while driving. It operates BOTH front and rear brakes (acting on ALL four wheels) and gets you to a standstill as quick as possible. This is as an added safety measure should the driver be incapacitated, the passenger can actually bring the car to a safe, quick and controlled stop by lifting (and holding) the parking brake lever.

2: On a modern ABS system, there is no way a normal driver can modulate the brakes better and get a shorter brake distance without ABS. The ABS system these days modulates the brakes so fast that it keeps the tires at almost optimum slip during the entire braking process. Optimum slip is where you have the highest degree of friction between tires and surface.

During an emergency brake, you will get the highest retardation (deceleration) just before you lock the wheels, then the ABS takes over and tries to maintain optimum slip, but deceleration falls slightly (but not nearly as much as it would do with locked brakes). This transition between a slightly better deceleration and "ABS braking" often feels like a "acceleration" or loosing braking power to the driver. I have heard many drivers involved in accidents explain that they braked hard, but felt the brakes "stopped working" and that the car "gained speed". Especially at wet or slippery roads. That IS a placebo effect, the brakes are still hard at work but it is not able to get as close to optimum slip as when the tires almost just locked up before ABS kicked in. This effect is even more pronounced on a non-ABS car as friction is far lower when the tires are locked.

The deceleration graph on any emergency braking will have a sharp rise to a maximum before it falls slightly and then is held stable, either by the ABS or the constant friction of locked tires (lower friction than with ABS). On old ABS systems you could see the pulsation of the ABS system on a MAHA G-meter.

-

[singularity]

Originally Posted by Boss330

Two points:

1: The electric handbrake on the BMW (or like on any other European car with electric handbrake) also acts as an emergency brake while driving. It operates BOTH front and rear brakes (acting on ALL four wheels) and gets you to a standstill as quick as possible. This is as an added safety measure should the driver be incapacitated, the passenger can actually bring the car to a safe, quick and controlled stop by lifting (and holding) the parking brake lever.

2: On a modern ABS system, there is no way a normal driver can modulate the brakes better and get a shorter brake distance. The ABS system these days modulates the brakes so fast that it almost keeps the tires at optimum slip during the entire braking process. Optimum slip is where you have the highest degree of friction between tires and surface.

During an emergency brake, you will get the highest retardation (deceleration) just before you lock the wheels, then the ABS takes over and tries to maintain optimum slip, but deceleration falls slightly (but not nearly as much as it would do with locked brakes). This transition between a slightly better deceleration and "ABS braking" often feels like a "acceleration" or loosing braking power to the driver.

The deceleration graph on any emergency braking will have a sharp rise to a maximum before it falls slightly and then is held stable, either by the ABS or the constant friction of locked tires (lower friction than with ABS). On old ABS systems you could see the pulsation of the ABS system on a MAHA G-meter.

Thanks, answered pretty much what I was wondering. So my emergency breaking today was in fact optimal then. I guess the sensation of a longer braking distance was because of a smooth ABS grind with a dopy sense of acceleration.

[Boss330]

Originally Posted by singularity

Thanks, answered pretty much what I was wondering. So my emergency breaking today was in fact optimal then. I guess the sensation of a longer braking distance was because of a smooth ABS grind with a dopy sense of acceleration.

Yes possibly, and also the psychological effect of having a car in front of you that you want to avoid...

[B-1Pilot]

Originally Posted by Marcus Frost

As someone who has both:

1.) Driven an ABS car without rear brakes (long story)
2.) Had extensive experience with traditional handbraking in performance driving

What you are implying makes no technical sense. Not only do rear brakes do relatively little work, especially in situations where the brake pedal is used firmly, the effective "locking" if the rear wheels defeats the purpose of ABS (anti-lock brakes). In essence, ABS systems are designed to modulate brake system pressure so that the wheels do not lock up. When wheels lock up they not only compromise braking distances, but they also introduce instability into the braking process.

So unless BMW built in a whole separate programming logic into their stability control program that takes into account the different dynamics of locked rear wheels, you are likely experiencing a placebo effect. In other words, hand braking does not reduce braking distances or enhance braking performance, it actually does the opposite.

Have you ever seen people hand brake in professional racing? Yes, you have, in rally and drifting - two forms of racing where the introduction of instability is actually necessary.

Maybe instead of spouting off a bunch of assumptions, just dont comment if you dont know.

What Boss ends up explaining in the following posts is straight out of the M5 manual, the M5 brochure, and is in multiple tech videos from BMW. Definitely not a placebo effect and not sure why you would tell someone it is...

[ColdList]

Originally Posted by B-1 Pilot

Definitely not a placebo effect and not sure why you would tell someone it is...

I think Boss is saying that it is a placebo effect in essence. In any case, he sure nailed it with his answer.

[Neil McRae]

on bmw's hit the pedal hard and hold it for extra braking power. perhaps drive slower where parked cars are also.

[Neil McRae]

actually anyone here on road fly about 10 years ago on the m3 boards? remember PYboy? drove a lot like singularity, ended up dead and his girlfriend almost dead when he a lamp post at 100. car was a mess. very sad.

[singularity]

Originally Posted by Neil McRae

on bmw's hit the pedal hard and hold it for extra braking power

No shit Sherlock I thought a hard quick tap was enough...

Originally Posted by Neil McRae

perhaps drive slower where parked cars are also.

Originally Posted by singularity

...almost hitting an inappropriately parked car on a road or even a highway.

Originally Posted by Neil McRae

actually anyone here on road fly about 10 years ago on the m3 boards? remember PYboy? drove a lot like singularity, ended up dead and his girlfriend almost dead when he a lamp post at 100. car was a mess. very sad.

You seem to be post farming, with reading and writing not being your strongest traits, but I'll tell you that I haven't had any car accident in my life. Depending on time, place and definition - street racing/spirited driving in my society are often very safe and more responsible to other drivers compared to many book-taught newbies who pilot their cars like a monkey with a grenade. I'll tell you another story, there was a witty lad from Bromley who liked to rice on racetracks, like you. He died in an accident on a race track with a courtesan in the passenger seat. When they retrieved the corpses, his penile organ was found from the woman's mouth

[JOHNBMWM5]

Originally Posted by singularity

No shit Sherlock I thought a hard quick tap was enough...






You seem to be post farming, with reading and writing not being your strongest traits, but I'll tell you that I haven't had any car accident in my life. Depending on time, place and definition - street racing/spirited driving in my society are often very safe and more responsible than some book-taught jackasses. I'll tell you another story, there was a witty lad from Bromley who liked to rice on racetracks, like you. He died in an accident on a race track with an escort courtesan. When they retrieved the corpses his penile organ was found from the woman's mouth

Very insulting if you ask me.

[singularity]

Originally Posted by johnbmw6

Very insulting if you ask me.

Sorry about that man, but that's reality nonetheless. I haven't developed a skin thick enough to ignore the post, especially since this isn't the first time the bachelor troll takes aim at me.

[JOHNBMWM5]

Originally Posted by singularity

Sorry about that man, but that's reality nonetheless. I haven't developed a skin thick enough to ignore the post, especially since this isn't the first time the bachelor troll takes aim at me.

Just "ride it" I do.

[avlnch]

Does the electric parking brake behave differently than the manual parking brake in the E60?

I would rather have the manual.. you can quickly disengage and roll or accelerate back or forward. With the electric, you have to give it a few seconds to disengage before you attempt to move the car.

It's almost like a "comfort feature" I could do without. But I learned to deal with it.. not a huge deal.

[singularity]

Originally Posted by avlnch

Does the electric parking brake behave differently than the manual parking brake in the E60?

I would rather have the manual.. you can quickly disengage and roll or accelerate back or forward. With the electric, you have to give it a few seconds to disengage before you attempt to move the car.

It's almost like a "comfort feature" I could do without. But I learned to deal with it.. not a huge deal.

I read the manual, it says to pull and hold it for emergency breaking. It takes about 2 seconds to engage. For example on M6 E63 I can make a sequence of pull/release to drift in slaloms or to make a 'U' turn and whatnot, on the electric brake it's not possible, it just stops the vehicle. I think it's just a direct inheritance from 5 series, VW passat etc also have it.

It serves its purpose - to stop the vehicle in the shortest and safest way possible, but I'd say that handbrake also among some of the lost 'fun factors' from the previous generation, among S85 V10, exhaust, steering etc

[nugent]

Originally Posted by B-1 Pilot

Maybe instead of spouting off a bunch of assumptions, just dont comment if you dont know.

What Boss ends up explaining in the following posts is straight out of the M5 manual, the M5 brochure, and is in multiple tech videos from BMW. Definitely not a placebo effect and not sure why you would tell someone it is...

zacly.

[Jay-K]

hate when the ABS interfere during the braking process, especially during hard braking.. does anyone know how this works?

[Marcus Frost]

Originally Posted by B-1 Pilot

Maybe instead of spouting off a bunch of assumptions, just dont comment if you dont know.

What Boss ends up explaining in the following posts is straight out of the M5 manual, the M5 brochure, and is in multiple tech videos from BMW. Definitely not a placebo effect and not sure why you would tell someone it is...

So what you are telling me, and may very well be the case, BMW is has said that in order to extract optimal braking in "emergency" situations you need to master the technique of pulling up on the small emergency brake switch? As if there isn't enough going through your mind in such a situation?

Why would optimal threshold braking not be modulated by the actual brake pedal, rather than the awkward, difficult maneuver that involves a small ebrake switch? Seems completely asinine to me. In emergency braking situations both of my hands are firmly planted on the steering wheel, where they should be, not fiddling around trying to stick one of my fingers under the emergency brake switch.

I apologize if my experience, and really common sense logic, has not prevailed in this discussion. I guess it was fooling of me to think that there was no possible way a car maker would actually tell you to optimize emergency braking, pull this tiny lever awkwardly positioned in such a place that unless you practice it 1000 times you would never be able to actually do in an emergency situation. This also obviously disregards the fact that in addition to ABS, the stability control built into this car is also incapable of properly executing an emergency brake procedure without pulling on said switch.

[vdubpower]

Originally Posted by singularity

Had an unfortunate moment today and thought I'd share. I've had several dangerous situations of almost hitting an inappropriately parked car on a road or even a highway. To keep it brief, I was in a situation when I was accelerating at around 150 km/h and saw a parked car about 250 meters away.

The moment I realized it's parked I floored the pedal hoping my car would stop before the 'deadline'. ABS kicked in as soon as I started breaking and it felt to have significantly increased my braking distance, maneuvering was not an option as I didn't want to make unexpected moves on the road. When there was about 80 meters left (and heavy traffic on other lanes) I realized that my car won't come to a standstill when I expect it and I was damn sure I would hit the parked car - this is when I found a small opportunity gap on the left lane and 2-3 meters before hitting the parked car I dived to the left lane.

I was lucky a good fellow driver realized I would have to change lane or hit the car in front of me and gave me a chance to move to his lane. Needless to say I was very thankful to him. I drove to a quiet speedy road and for the first time tested the electronic handbrake AND full stop brake and it seemed to have shortened the ABS distance and planted the car very firmly.

Is the electronic handbrake designed to be used at high speed situations similar to mine today? Has anyone tested actual braking distances with Brake/Handbrake/Brake+Handbrake?

WTF, why are u driving so fast in parking lots

[turbolag]

Originally Posted by vdubpower

WTF, why are u driving so fast in parking lots

Parked on a road....

Not parking lot...

[Boss330]

Originally Posted by Marcus Frost

So what you are telling me, and may very well be the case, BMW is has said that in order to extract optimal braking in "emergency" situations you need to master the technique of pulling up on the small emergency brake switch? As if there isn't enough going through your mind in such a situation?

Why would optimal threshold braking not be modulated by the actual brake pedal, rather than the awkward, difficult maneuver that involves a small ebrake switch? Seems completely asinine to me. In emergency braking situations both of my hands are firmly planted on the steering wheel, where they should be, not fiddling around trying to stick one of my fingers under the emergency brake switch.

I apologize if my experience, and really common sense logic, has not prevailed in this discussion. I guess it was fooling of me to think that there was no possible way a car maker would actually tell you to optimize emergency braking, pull this tiny lever awkwardly positioned in such a place that unless you practice it 1000 times you would never be able to actually do in an emergency situation. This also obviously disregards the fact that in addition to ABS, the stability control built into this car is also incapable of properly executing an emergency brake procedure without pulling on said switch.

No one has said that you, the driver, should pull the E-brake lever in an emergency... If the driver becomes incapacitated, the passenger has a decent chance of bringing the car to a halt with a modern electric handbrake/E-brake. Re read my post where all of this was explained.

The most effective braking comes from the driver pushing hard on the brake pedal and let the ABS modulate the brakes. The electric handbrake is just an added safety device should the driver not be able to brake anymore (or if the brake pedal falls off... )