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  #1  
Old 02-20-2002, 05:19 PM
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Electronic brakes in new E-class

A couple other MB lists are talking about a review in a UK magzine about the new MB E-class. It comes with electronic brakes and here is the relavent part:

Then there's the electronic brakes. They will stop the E amazingly quickly and safely, with computers working out the optimum way to bring the car to a halt depending on how the driver has hit the pedal, road conditions and speed. But while they are undoubtedly powerful and very clever, too, the boffins haven't quite got the response right yet. The computer control can't seem to work out how much braking pressure to deliver, and a quick
dab of the pedal to wipe off speed before a corner will often result in more deceleration than you may have intended.
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Old 02-20-2002, 06:25 PM
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The new SL due for release next month ALREADY has this braking system. ALL of the Dealer shop & parts people had training on this super hi-tech car.
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Old 02-20-2002, 07:01 PM
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Now my concern is what if this system fails as many other MB electronic systems? MB has this "limp home" thing on ASR and other stuffs, but will the brakes "lock home? LOL.
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Old 02-20-2002, 08:32 PM
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Some perspective:

At a seminar a while ago electronic brakes were discussed as part of the growing need for 42 volt electrical systems. The smirks and chuckles filled the room untill the instructor pointed out how similar doubt had accompanied the onset of hydraulic brakes in 1940 (or so). After all can you imagine the lack of confidence one would feel going from the positive action of cables to the use of fluids to accomplish the same thing.
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Old 02-20-2002, 10:17 PM
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From what I have read, a conventional hydraulic system serves as backup, but for the front wheels only.

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Old 02-20-2002, 10:23 PM
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Things can go wrong with most anything, but here's what I know already about Sensotronic Brake Control (SBC):
In the event of an electrical failure, there is a hydraulic over-ride in the hydraulic unit (called a seperation valve) that will allow normal hydraulic pressure to be applied, although without power brakes.
The system is designed to "feel" like a normal brake pedal, but in normal operation, an electronic sensor is really determining what is occurring at the wheels. An obvious benefit is that each wheel is capable of being provided the correct amount of pressure.
A couple safety relevant advantages are called pre-charging and dry braking.
Precharging means that if the system detects your foot coming off the throttle rapidly, the brake system will bring the brake pads out just to the rotor, to be able to apply more rapidly when the brake pedal is depressed (not until you step on the brakes will they actually apply).
Dry braking is a feature where the brakes are applied very briefly and lightly about every 5 to 10 minutes if the wipers are operating. This action keeps a film of water from developing on the rotor surface to help reduce stopping distances in wet weather.
There is also a feature called "Softstop" which reduces the "jerk" you feel at the end of a stop. It doesn't work during panic stops.
It's going to be tricky to remember the safety precautions when servicing the brakes, as the brakes automatically apply if the driver or passenger door is opened, among other reasons, so the system has to be deactivated using the SDS computer before doing any brake work. Can get really messy if you forget that!
Gilly
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Old 02-21-2002, 04:27 AM
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Quote:
Originally posted by gillybenztech
Precharging means that if the system detects your foot coming off the throttle rapidly, the brake system will bring the brake pads out just to the rotor, to be able to apply more rapidly when the brake pedal is depressed (not until you step on the brakes will they actually apply).

There is also a feature called "Softstop" which reduces the "jerk" you feel at the end of a stop.
One reason why twin-piston (or 4-piston or higher) brakes with fixed calipers/floating rotors are superior to those with single-piston/floating calipers/fixed rotors is that both sides of the rotor are engaged more quickly than with single-piston/floating caliper design (with single-piston/floating calipers, the rotor surface on the piston side of the caliper is engaged first, and as the caliper slides, the other surface is then engaged).

With "precharging", you can get superior brake response without requiring the (more expensive) fixed caliper/floating rotor design.

And that "softstop" feature is really neat. But then again, the skill of doing a softstop manually will also become a lost art - it's one of those subtle skills for smooth driving.

But one of the biggest advantages of e-brakes is that it is the ideal setup for traction control and stability systems, where individual wheels have to be braked.

They said that they removed the "pulsing" of the ABS, primarily because the reaction of the majority of drivers when they sense this is to ease up on the brakes (and hence the need for Brake Assist). But this is precious feedback for the driver.

they better have wiring harnesses better than those in the 94-95 W124s. You don't want electrical shorts in this one ...
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