Electric Handbrake / Emergency brake - Why? 10

[NickJ67]

Whats the reason for manufacturers moving towards electrically actuated, push-button handbrakes these days?

Having recently had to deal with one as fitted to the VW Passat, I have to say that it alone would prevent me from buying/leasing what is otherwise a pretty good car - such a pain to use when maneovering on a steep slope. I have also had the entertainment of watching my neighbor having to deal witha malfunctioning one on her Renault Scenic (non-release scenario).

Seems to me that they must be more expensive to fit and more prone to malfunction than a good old fashioned cable and lever arrangement - what am I missing? Am I a luddite....?

Regards

Nick

 

[moon161]

Frees up compartment space for cupholders. Need I say more? Sounds awful. What if the battery dies and it's not in gear? What if the wire comes off the negative terminal on the battery comes off at speed? Motor cuts out, no e-brake, stored vacuum will be all you have to stop with.

Had a mech e brake freeze up this winter on me. When I tried to go, the differential kicked, and I didn't have enough traction to drag the locked wheel. Finally rocked it enough to get the car moving and drag the locked wheel till it freed up. Good laugh looking back.

 

[MikeHalloran]

I'm guessing that electric handbrake actuators (never heard of 'em before) are cheaper, >as installed<, than cables and ratchets, because a harness is more flexible than a stout cable, so can be routed through a cramped area without great difficulty, and snapping a connector is easier than making up a robust mechanical connection, and you don't have to stock a low-markup mechanical part for every different model or wheelbase, just one universal expensive part.

I will also be eliminating vehicles so equipped from my short list, because:
- I'm guessing (again) that they're impractical to use for slowing the car down without energizing the brakelights, as is occasionally desirable.
- They're already demonstrating a finite failure rate.
- They're going to be expensive over the parts counter.





Mike Halloran
Pembroke Pines, FL, USA

 

[evelrod]

I'm pretty well on record as being against all this fly by wire control systems. An e-brake/parking brake---actually, when was the last time anyone called it an emergency brake? Sounds like the bean counters have a hand in this somewhere...or they have a crack problem in the engineering dept. !

Rod

 

[dgallup]

I don't really know how these are actuated but I suspect that they can be implemented with nothing more than a switch on vehicles that already have both ABS and stability control. These vehicles already have all the electronics, pumps and valves to actuate the brakes when ever they see fit on which ever wheel they choose. You have already given your life over to these systems while traveling at high rates of speed, why not while parked?

"- I'm guessing (again) that they're impractical to use for slowing the car down without energizing the brakelights, as is occasionally desirable."

I won't be buying one of these soon either but to me it's a lot less serious than the little rat fink black box spy's they are building into most new cars.

 

[GregLocock]

Mechanical park brake systems are expensive, or rubbish, or expensive /and/ rubbish. I've worked on all three types! They take up huge amounts of real estate under the car in very awkward places, and need a lot of adjusting, typically.

My guess is that most drivers don't really use them any more, except as park brakes.



Cheers

Greg Locock


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[patprimmer]

On an automatic they could be activated automatically by selecting the park position.

I would opt out of it if I could, but it would not be a major factor in my choice of a new car.

A lever to control a linear motor would be real nice especially if there was a feed back device for real feel in the lever.

Regards
Pat
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[evelrod]

Ah...Then there is that 'little' Toyota recall thing recently!!

More Murphy...."If it can go wrong, it will"!

Rod

 

[MikeHalloran]

Okay, I admit it, here in flat SoFla I rarely bother with the parking brake on my one automatic-equipped vehicle.

But every summer, I go to upstate NY, which has fairly serious grades, even in places where you'd like to park. E.g., the ancestral home's driveway is steep enough that it's very difficult to disengage an automatic's parking pawl unless you seriously applied the parking brake before engaging the pawl.

I don't terribly mind using the service brakes' friction surfaces for a park brake, as used to be standard here in The Colonies, but I have a serious problem with relying on their hydraulics for that purpose. Of course, this kind of crap is never an issue while the car is in warranty and uncorroded, so it may be forced down our throats, but I'm not happy about it.



Mike Halloran
Pembroke Pines, FL, USA

 

[BrianPetersen]

For those of us who drive in winter conditions, the occasional ability to override the ABS/ESP nanny nonsense is extremely useful. The cable operated mechanical brake (on a hand lever, not a foot pedal!) works for this.

Useful for: Getting a car to turn when it doesn't want to (plowing straight on a slippery surface), getting a car to stop when the ABS won't let it (building up a wedge of snow or gravel in front of a locked wheel helps).

I doubt if the pushbutton/electronic method will overrule the ABS ... and you can't modulate it.

 

[Lou Scannon]

evelrod,

I like to think of myself as a crack engineer... Are we going to have to take this to the pub?!! ;-)

 

[izzmus]

The only one I have direct experience with used an electric motor to pull on the standard cable. It engaged any time the ignition was cycled off. Reason? Besides the why-not factor, it means there is one less hole in the body, that much less to do on the assembly line, no pedal or lever to work around when designing the interior... and it has a "neato" factor like pushbutton start.

I have seen designs that were incorporated in the caliper, but I suspect that laws requiring separate cable and hydraulic actuation of brakes may be preventing that from hitting the roads, if it's not out yet.

 

[btrueblood]

"- I'm guessing (again) that they're impractical to use for slowing the car down without energizing the brakelights, as is occasionally desirable."

Mike, have you been moon(shine)lighting again?

"My guess is that most drivers don't really use them any more, except as park brakes."

Oh, Greg, how could you say that? Though it is probably true, given that 99% or so of US drivers won't or don't know how to drive a stick. I use mine pretty often, but then, I drive a stick in a hilly area.

 

[SomptingGuy]

I use mine when stationary and my right foot starts to ache. (manual of course)

- Steve

 

[NormPeterson]

[/quote]My guess is that most drivers don't really use them any more, except as park brakes.[/quote]

I get that there are likely to be some design and assembly benefits. There may or may not turn out to be any maintenance & repair benefits; I think it's too soon to tell. But a secondary braking system is something that should first and foremost be user-friendly.

If the buttons aren't located any better in other cars than the one in my wife's new Subaru is, they'll be all but useless in an emergency. Down on the left side of the dash, nearly out of reach, not where you need to be looking when you need it in a hurry, and not something you should be wasting any time fumbling with. If you ever wanted to get people away from using anything but the footbrake, this seems as good a way as any to go about it.

I don't like it at all, for the above plus most of the reasons already mentioned. But I suppose that it gives away less functionality - at least with respect to getting a car to turn in on a slippery surface - with that car's AWD than it would with anybody's FWD.

I think the manual means of releasing the Subie's P-brake involves 200 revolutions or so with a little hand crank that fits into something down under a body plug. Even though I rarely use any P-brake - no thanks.


Norm

 

[GregLocock]

I haven't been involved with an electrically operate Park brake, so I don't know how the FMEA deals with all the thousand different things you think will go wrong.

Down the track you could imagine getting rid of the thing entirely, and using the ABS pump to keep the brakes energised when parked. That gets rid of the redundant system of course, but we don't have a redundant steering system, and that is more important.

Cheers

Greg Locock


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[patprimmer]

Since the 1970s I think most cars have at least separate hydraulic systems to pairs of wheels. I have not looked at modern ABS/traction control/dynamic handling control or whatever they call it when the computer decides to apply brakes when you are trying to drift it through a corner. Are they 4 separate circuits.

Certainly if there are at least two circuits that work independently if a hydraulic or electronic system fails you have redundancy foe everything downstream of the pedal mechanism.

Regards
Pat
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[GregLocock]

All 4 brake pipes go into the ABS pump, but it only has one power lead.



Cheers

Greg Locock


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[patprimmer]

So if the pump fails, do the brakes still work effectively without ABS and is it still dual circuit from the MC to the calipers.

Regards
Pat
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[BrianPetersen]

ABS-equipped cars still have a dual-circuit master cylinder. The system defaults to operating like a normal dual-circuit non-ABS system if the ABS unit fails.