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      06-19-2009, 02:51 PM   #1
teagueAMX
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Electro-Mechanical E-Brake

Just curious - FWIW

I'm aware the "P"/e-brake is a electro-mechanical device actuated by a switch, rather than a purely mechanical lever.

The curious thing is this: is it held by battery power only (I assume BMW engineers wouldn't do it that way) or is actuated by an electrical solenoid that engages a fail safe mechanism?

Is it in the transmission like a conventional parking brake, or does it actually apply force to a conventional disk (inner drum) brake at the rear wheels?

Again, just a curiosity - never heard anyone complain about it. Some of the new BMWs continue to employ a purely mechanical e-brake lever, so it got ta think'n .

Last edited by teagueAMX; 06-19-2009 at 08:39 PM..
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      06-19-2009, 06:30 PM   #2
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Good question.
I use the auto park at long stop lights and it lets just drive off so was wondering if it was
link to trans somehow. hopefully someone can enlighten us.
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      06-19-2009, 08:22 PM   #3
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Quote:
Originally Posted by dmlgc View Post
Good question.
I use the auto park at long stop lights and it lets just drive off so was wondering if it was
link to trans somehow. hopefully someone can enlighten us.
Sales person told me auto park feature "gently" sqeeze's brake rotor with same brake pads used to stop the car.
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      06-19-2009, 09:08 PM   #4
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Quote:
Originally Posted by dmlgc View Post
Good question.
I use the auto park at long stop lights and it lets just drive off so was wondering if it was
link to trans somehow. hopefully someone can enlighten us.
Quote:
Originally Posted by bak View Post
Sales person told me auto park feature "gently" sqeeze's brake rotor with same brake pads used to stop the car.
Cool - sounds like BMW is using the same tek they use for the hill holding feature with its manual transmissions. Smart people over there in Deutschland. Nowadays, the brake system are all controlled by the computer anyway (i.e., anti-lock brakes, traction control, launch control, etc.). Someday we'll be braking by wire.

I'm sure our bimmer friends have thought it but what if your battery goes dead, and you car is on an incline, what keeps the e-brake engaged; would it roll?
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      06-20-2009, 05:19 AM   #5
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This is how bmw explain it:

Quote:
Electromechanical Parking Brake.

Starting off on a slope, in stop-and-go traffic or whenever the engine is turned off: the Electromechanical Parking Brake ensures your BMW stays comfortably and reliably at a standstill whenever required.

Working together with Dynamic Stability Control (DSC), the Electromechanical Parking Brake controls all braking processes whenever the vehicle is not moving. If the engine is running, it operates hydraulically via the DSC brake system. If the engine is switched off, electromechanical brake cables support the function of the conventional handbrake.
The Electromechanical Parking Brake can be activated by pressing a button on the instrument panel or, depending on your BMW model, on the centre console. It also offers an autostop and hillhold function.

Autostop automatically activates the parking brake whenever the vehicle comes to a halt; it disengages the moment you touch the accelerator. In vehicles with automatic transmission, it is no longer necessary to keep the brake pedal applied to prevent vehicle creep when stopping in gear, such as in stop-and-go traffic or at traffic lights. This makes city driving significantly more comfortable.
Hillhold automatically applies the parking brake whenever your BMW stops on a slope, preventing unwanted rolling, and disengages it when you start off again.
http://www.bmw.com/com/en/insights/t...ing_brake.html

I'm a fan of these "auto-release on gas" button type parking brakes - it's a little aggressive in terms of when it applies via the auto-hold but that's just something to get used to.
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      06-20-2009, 10:19 AM   #6
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That's excellent. I knew BMW thought it through very well. I just didn't know how they did it. So for the most part the backbone of the systems are conventional mechanical systems, that happen to be controlled by electronics. I particularly liked the part that says:

"If the engine is switched off, electromechanical brake cables support the function of the conventional handbrake."

Just to give you an idea about how anal I am about certain things. Back in the mid-1980's I purchased a new car with full electronic engine control. After parking it in my driveway I lifted the hood and disconnected a computer control plug to see if the thing would run with out it. A dashboard light came on, the idle was a little rough, but it ran OK. You could even drive it that way if you had to.

I put together computers back in those days and knew how unreliable they could be so it was reassuring to have that knowledge. I used to be that way about elevators, too, but after researching all the safety features, no problem.
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      06-20-2009, 10:42 AM   #7
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I had an a5 before the x6 and that had a button-brake that released on gas (didn't auto-apply though). You could feel that mechanically "ratchet" the park brake when the button was pulled - the x6 is a lot less obvious about it.
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      06-20-2009, 09:26 PM   #8
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Thanks
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