Searched the forum but didnt find anything on this...
Traffic opened up in front of me so I laid into it and at the exact same instant a guy pulled into my lane just ahead of me. I jammed on the brakes, and felt the ABS pulsing (tires were screeching too.) Then comes the weird part - I let off the brakes, but for another half-second the car kept braking - hard! That was a half second of terror because I was picturing the car behind me slamming into me. Luckily no one was close, but now I have less confidence driving the car iif it is going to decide to brake hard wth my foot off the pedal. Any ideas? Was it because I went from hard acceleration to hard braking? Was it the esp detecting wheelspin while braking and it decided to keep braking? (ESP was "off") Brake pedal sticking?

On a side note - why do people click on their turn signals AS they are changing lanes instead of before? At that point I can already see they are turning so doesn't that defeat the purpose of signaling a turn?

 

humm, i thought the ABS pulsing was like spinning on a wet surface rain snow ice ect...

 

My guess would be the computer kept the abs on until the car was back in control.

 

My car did the same thing after a hard stop - right after braking I stepped on the gas but for about half a second there was no power. Like Robby, I think the computer kept control for a moment afterwards to ensure all was well.

 

Dude,
That's a WHOLE new thread there! Don't get us started!

 

Most likely the brake assist (BAS). Basically, during a panic stop, the brakes apply full force (automatically) even if you don't push the pedal all the way down, or if you let up to reduce brake force. The computer senses how quickly you push the pedal and recognizes it as an emergency situation. Mercedes believes that drivers sometimes under estimate an emergency stop and wait too long to apply full brake force; the car steps in and does it for you.

"The Brake Assist System (BAS), an electronic system by Mercedes-Benz, interprets the braking behavior of the driver and initiates the full braking effect when it identifies an emergency situation. This reduces the braking distance substantially.

Here is the engineering foundation for BAS:

Conventional braking systems usually use engine vacuum to increase braking capability. Instead of relying solely on vacuum power to provide effective brakes, an electric pump pressurizes brake fluid to provide power assist for BAS and the necessary brake force for 4ETS.

The pressurized brake fluid is stored at about. 180 bar (2600 psi!) in a reservoir known as the accumulator. From the accumulator the high pressure brake fluid is supplied to the hydraulic operating cylinder in the master cylinder assembly. Commands to utilize the pressurized fluid comes from either 4ETS or BAS. When the brakes are applied and BAS deems it necessary, a lever connected to the brake pedal releases varying amounts of the high pressure fluid to assist in stopping the car.

Here is what BAS does for you:

Most drivers, under normal braking conditions as well as under emergency conditions, start out with little brake pressure and whenever necessary they will increase their pedal effort. In an emergency this behavior leads many times to a crash since the car could not be stopped in time. Those situations require maximum pedal pressure from the beginning - if necessary the effort can be reduced later in the process.

With other words most drivers do not use the ability of the brakes to their advantage - BAS automatically corrects that. The system recognizes emergency situations within milli seconds and releases pressurized brake fluid into the system as soon as the driver touches the brake pedal. As soon as the driver releases the brake pedal, BAS kicks back into a standby mode.

BAS creates a much higher stopping force for emergencies than most drivers are ever able to generate. By doing so BAS helps to prevent accidents


Just another good reason to drive a car made by Mercedes-Benz"

 

O crap. I don't even have BAS or ESP on my car. I hope my Brabus/Alcon 6 + 4 pistons work....

The way I see it, BAS might be bad if you are on a track and brake hard before a turn; means you won't be able to get on the throttle until the brakes let off.

 

Its the stability control as I missed a gate on the autocross circuit and went full lockup and then full power without any delay.

Difference was I had the two fuses (#14 and 15 I believe) pulled and no effect.

Enjoy WOODY

 

It's called Emergency Brake Assist. It's in the owner's manual. Basically, it's another nanny that is supposed to keep us from dying. What it does is sense the force and speed in which you apply the brakes. In an event like you describe it assumes you are trying to avoid a crash, which you were. It keeps the brakes applied for a couple of reasons. First, even though ABS brakes have been around a long time, there are still driver's out that that have never experienced ABS in action. The common reaction when the brake pedal starts to pulsate is it scares the driver, and they lift off the brake causing a crash anyway. The Brake assist takes this into account and keeps the brakes applied briefly to make sure you don't really want to stop. The other thing that it does is apply 100% of all available braking force at that moment. Some people can't/don't push the pedal hard enough, so if the pedal is hit hard and quickly, it takes that as a panic stop and applies 100% of the braking force weither you push the pedal 100% or only 80%. I hope that makes sense. I saw a video on it when I worked at the Chrysler Dodge dealer a couple of years back. I can see why it would alarm you if you didn't know the feature was there, but I think it's pretty cool...

 

I felt this on the track once or twice. Didn't kill my turn entry speed and actually kept it about right as I had waited too late to brake. The car just did a little extra... where I would have let up sooner and possibly risked to hot of an entry into the turn.

I'll leave my ESP and BAS functional for a while longer while I learn better cornering techniques. When the traction control light or BAS no longer assists me, then I'll be comfortable with turning off the traction control when I'm at the track.

Until then, I'll let the systems save my sorry A$$ from time to time.

 

MMZ, I had mine off the other day scuffing in new tires, hit a favorite hair pin of mine, like I have done for years, powered out after hitting it hard, traction control caught, like putting on the brakes, had to go with it, did a 360 and kept on going a little ashamed since this has never happened before...turns out that even though I had the traction control off, and even though I had a tune, parameters changed, the damn car still has a memory and went back to its "save" feature...I have to reset before playing so it erases the memory of my casual driving habits...what a car...

 

Keep in mind that you can't turn it off completely unless you're in "dyno mode" (or pull the fuses), and I have never heard of a tune that affects anything in the ESP. Also, if you did a 360, it wasn't caused by the traction control. Don't forget, for best traction, tires have to be broken in too. You should do some normal driving before hitting the hair pins.

 

IMHO.....Leave it on, the system saved the car and my sorry butt twice. You can pull fuses, turn it off, it will still step in if it thinks you are gonna buy the farm and try and straighten you out. A must have over 110 mph.