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[tidla]

An after thought, I do not really like the electronic handbrake, not sure what would happen with a total electrical failure..... :-/  HGV/PSV break failure puts the brakes on...
Also, on our Omega's we always use the hand brake, I put the hand break on before puttining it in Park. The hand brake needs to be used.....

agreed. hgv brakes work on the principle of air to operate the primary braking system and air depletion to operate secondary/parking brake actuation.

hydraulic brakes can, by there properties of water absorbsion fail and should have a secondary braking system available, if i have read posts correctly..

[Squidy]

i really dont like the idea of a electric hand break!
Americans got something right for once calling it an e-break or emergency break, because its is a good old cable backup should hydraulics fail!
my friends passat had his electric hand break jam on 3 weeks ago, cost him £800 to fix! for that price ill stick with my old fashioned hand break thanks!

[Kevin Wood]

thirdly, it is a cost thing. The manufacturer will have a relatively advanced ABS system, doubling as Traction Control and stability control. One of the routines will be to apply the brakes to a spinning wheel to regain traction. The cost of another switch is much more attractive to the manufacturer than some special brake calipers, the levers and cable. Probably about 20p vs £10, which is a really big thing in car-manufacturer land. I know one company where the suggestions scheme will send anyone who reduces the cost of a car by more than £1 on a holiday in the Bahamas.

So they're hydraulic? Never looked into how they work but I didn't imagine for a minute that it would be a hydraulic setup pumped up by the ABS modulator. I assumed at least a motor at the caliper winding on a mechanical brake mechanism.

I can see why they don't hold well now, and I want one even less.

The argument as to whether a hydraulic handbrake is legal has been done to death in kit car circles. Anyone I'm aware of who has tested the concept with the powers that be have received an unequivocal "no".

Kevin

[Shimmy]

The electronic hand brakes most certainly work whilst in motion.  Going back to the question if they could be used in a brake failure, yes they can. 

I saw a video on youtube last week where an Audi TT RS was bombing round a track and his brakes suddenly failed, he quickly applied the electronic brake at 220km/h (!) which sent his car into a spin and managed to stop without involving anyone else coming out without a scratch.  Potentially saved his life.

I'll see if I can find the video.

[Shimmy]

Seems the youtube video was removed by the user.

But the video has been reuploaded by someone else here:

http://www.streetfire.net/video/audi-crash_2063815.htm

Skip to 10 mins in to see the application of the electronic handbrake.

[Psychoca]

An after thought, I do not really like the electronic handbrake, not sure what would happen with a total electrical failure..... :-/  HGV/PSV break failure puts the brakes on...
Also, on our Omega's we always use the hand brake, I put the hand break on before puttining it in Park. The hand brake needs to be used.....

But at least on these you would get a warning of low air, and unless you had an immediate failure of both air tanks (unlikely), the brakes wouldn't come on instantly

Even with immediate failure of both air tanks the brakes would come on...  The air tanks hold the brakes off, if there is no air the brakes slam on...  I would have thought with electronic handbrakes, a solonoid would be held open while the hand brake is off... When HB is on it would effectively close the solonoid (It would take the mickey if the battery died and so would the handbrake when parked on a hill)...

I personally would prefer a mechanical device that I can rely on should I need it...

[Sixstring]

Done some investigation on this........(cos I'm interested.....)

there appears to be three ways these electronic handbrakes are activated,

1) electronic activation via ECU pressurising ABS (AUDI VW SKODA)
2)solenoid activating remote "slave" type cylinder in the braking system plumbing, but only on the rear wheels (MERCEDES)
3)remote hydraulic actuator, pressurising ALL 4 wheels, but not activatable whilst vehicle is in motion (FIAT)

there is a dispensation within the MOT test to test them, tested by activation of "parking brake" then trying to turm wheels via rollers to calculate efficiency. My local MOT tester hates them, and says in his opinion they are dangerous, because they (whatever type employed) CANNOT be progressively applied to slow the car in event of brake fail, and because some of them are hydraulically assisted, will not work on a brake fluid leak situation.
I'm sure someone will shout me down here, but it seems to me, that in principle its ok, but practically, its not ideal, and takes some of the  "user input" out of driving a car, let alone the fact it can stop me doing drifting and handbrake turns!!

[Kevin Wood]

Hmm. Relying on hydraulic seals top stop your car rolling away is like working under it with a hydraulic jack as the only means of support IMHO.

The slightest weep from one of the slave cylinders (or even cooling of the brake components following a spirited drive and contraction of the calipers, disks, pads and fluid) and the pressure will be gone.

Kevin

[2woody]

I had no doubt that they were legal, it's just how that was in doubt. BUT OOF members have come to the rescue - well at least I think so anyway.

I have to give this sort of advice every day as part of my job, so I'm keen to keep abrest of these things.

..... and whilst the kit-car people may have asked for advice, that doesn't mean that the advice they've been getting is right or legal - just look at the "official" advice about retrofitting HiD

[Kevin Wood]

I had no doubt that they were legal, it's just how that was in doubt. BUT OOF members have come to the rescue - well at least I think so anyway.

I have to give this sort of advice every day as part of my job, so I'm keen to keep abrest of these things.

..... and whilst the kit-car people may have asked for advice, that doesn't mean that the advice they've been getting is right or legal - just look at the "official" advice about retrofitting HiD

Agreed. There's misinformation all over the place, of course. I've never dug deeper than the SVA/IVA manual, which I appreciate isn't the definitive bible on all things on the road but tends to dictate how kit cars are built.

I do remember that it specifies that the parking brake must be operated using a control independent of the service brake and, once applied, must be maintained on by purely mechanical means.

I thought that was the showstopper for a hydraulic handbrake?

I notice there's also a proviso that the secondary braking system can be fulfilled by one half of a split circuit service brake, so the parking brake is no longer regarded as an emergency brake and presumably it doesn't matter if it can be applied progressively enough to control the vehicle.

Kevin

[Sixstring]

ABSOLUTELY.

You've hit on it, MECHANICALLY operated and supplimentary.
Whilst hydraulic handbrakes have been used for years in rally cars, etc etc very few road card have had this facility. The ability to slow down a car using the handbrake in event of normal braking fail has been mandatory, so handbrakes that do not have this facility must be by definition unsatisfactory, and if they CANNOT be progressively applied to independantly slow the car illegal???
I'm also assuming that in event of an electrical fail or lossof total power, the handbrakes don't work, or release on "failsafe"??

Doesn't seem very safe to me.

[andyc]

On the new Astra J and the Insignia the electric hand brake still have cables going to the rear wheels.

What happens is the switch on the console works a servo that puls the cable

Andy

[2woody]

that Astra J solution seems like the worst of both worlds to me.

remember Kevin that the SVA / IVA manual isn't the definitive guide for what's allowed on the road, it's just what must be fitted to new kit-cars.

the key will be in Construction & Use vs. the MOT testers manual.

anyway, I'm on holiday now until Friday - have just spent the entire weekend going through 285,000,000,000 vibration readings looking for trends. need oxygen

[Entwood]

I've had a chat to a friendly MOT man .. and he informs me that the latest 2010 revisions to the MOT test manual have a new section on electronic braking devices.

The only on-line reference he was able to give me I've eventualy found ..

http://www.motester.co.uk/TradeMagazines/MOTTestingMagazine/2010MOTInspectionManualChanges.aspx

and the only mention is right near the end ,...

In the Brake performance section on page 3, there is the addition of a note regarding Electronic Parking Brake and to refer to VSI for instructions, there is also a note to use MOI 8 for the testing of prop-shaft parking brakes, and notes that apply to Class 5 and large Class 4 vehicles where an applied brake test may be required.

Can't find much more I'm afraid ... and I don't have access to the manual ..

[Phil]

On the new Astra J and the Insignia the electric hand brake still have cables going to the rear wheels.

What happens is the switch on the console works a servo that puls the cable

Andy

The reason for that is because the Insignia is sold with either a normal lever handbrake or the electronic push button one!!!

Obviously cost isn't the reason car makers are doing it otherwise why would both be available.

Oh and for reference i had two hire car Insignias last year, both '58 plate' 1.8 VVT  6 speed manual, one an SE spec with electronic handbrake one an S spec with a nomal lever