Vectra- strange handbrake behaviour

[ib]

I've recently bought a second hand Vectra, and was surprised by the
handbrake behaviour. If you are rolling slowly forwards, and slowly apply
the handbrake, nothing happens until suddenly both rear wheels lock up.
Also, while the car is still, and the handbrake fully on, you can roll the
car backwards and forwards an inch or so. I always thought that a handbrake
was intended to work as a secondary braking device in the event of the main
brakes failing, but it would obviously be dangerous the way mine are
working. However, it's just had an MOT so either this was missed or it is
acceptable (surprisingly).



So, as I'm a fairly advanced home mechanic I thought I'd take a look. It's a
slightly strange system where the main braking is provided by a disk, and
the handbrake by a drum. Anyway, from what I see of the design, the
behaviour above is exactly what I'd expect.



The cable operates on a lever which is fully floating, which forces the
drums apart. As the cable tightens, it will pull the front shoe forwards,
off the block that it rests on, until it meets the drum. Because of the
forwards motion, the front shoe will want to follow the wheel direction,
downwards, which will result in both of the shoes rotating slightly with the
wheel. But what this causes is the floating lever to be moved to the rear,
effectively increasing the tension in the handbrake cable pulling from the
front, and applying more braking force. There is therefore a runaway
situation which results in a rapid change between no braking at all and a
locked up wheel.



Anyway, I fully dismantled and cleaned it, and fitted new shoes, and
adjusted the top adjuster as well as I could, and was not surprised to see
exactly the same as before.



Is this really normal for a Vectra?





Thanks

 

[steveb]

Anyway, I fully dismantled and cleaned it, and fitted new shoes, and
adjusted the top adjuster as well as I could, and was not surprised to see
exactly the same as before.

It will lock the wheels!

What more do you want from an "emergency" secondary brake?

steveb

 

[Guest]

I've recently bought a second hand Vectra, and was surprised by the
handbrake behaviour. If you are rolling slowly forwards, and slowly apply
the handbrake, nothing happens until suddenly both rear wheels lock up.
Also, while the car is still, and the handbrake fully on, you can roll the
car backwards and forwards an inch or so. I always thought that a handbrake
was intended to work as a secondary braking device in the event of the main
brakes failing, but it would obviously be dangerous the way mine are
working. However, it's just had an MOT so either this was missed or it is
acceptable (surprisingly).



So, as I'm a fairly advanced home mechanic I thought I'd take a look. It's a
slightly strange system where the main braking is provided by a disk, and
the handbrake by a drum. Anyway, from what I see of the design, the
behaviour above is exactly what I'd expect.



The cable operates on a lever which is fully floating, which forces the
drums apart. As the cable tightens, it will pull the front shoe forwards,
off the block that it rests on, until it meets the drum. Because of the
forwards motion, the front shoe will want to follow the wheel direction,
downwards, which will result in both of the shoes rotating slightly with the
wheel. But what this causes is the floating lever to be moved to the rear,
effectively increasing the tension in the handbrake cable pulling from the
front, and applying more braking force. There is therefore a runaway
situation which results in a rapid change between no braking at all and a
locked up wheel.



Anyway, I fully dismantled and cleaned it, and fitted new shoes, and
adjusted the top adjuster as well as I could, and was not surprised to see
exactly the same as before.



Is this really normal for a Vectra?





Thanks

That's exactly what my Vectra estate (rear disc brake's) does.
Normal behaviour.
Dave

 

[ib]

Well, just something a bit more like all the other cars I've owned, like an
inceasing amount of braking force, in proportion to the demand input, rather
than something that's likely to put the car into an immediate slide or spin,
or wreck the tires.

 

[steveb]

Well, just something a bit more like all the other cars I've owned, like an
inceasing amount of braking force, in proportion to the demand input, rather
than something that's likely to put the car into an immediate slide or spin,
or wreck the tires.

That's unlikely. The behaviour of your handbrake at any sort of speed is
likely to be very much different to it's characteristics at walking speed.

Your handbrake works. It passed it's MOT, and Vauxhall were happy enough to
sell it without serious worries about product liability claims.

Find something better to worry about

steveb

 

[R. Murphy]

With your symptoms I would have immediately thought "Contaminated linings +
wet weather"" but I guess you have checked for that

Find a quiet bit of very wide road or a car park, and try just gently
applying the handbrke at varying speeds. ALWAYS keep the locking button down
so the ratchet is disengaged. This will give a feel as to how the brake will
really work in practice.

Better still, find a stretch with a slope.

 

[Alan Norris]

So, as I'm a fairly advanced home mechanic I thought I'd take a look. It's a
slightly strange system where the main braking is provided by a disk, and
the handbrake by a drum. Anyway, from what I see of the design, the
behaviour above is exactly what I'd expect.

It's not a slightly strange system - it is the norm nowadays for most
cars with rear discs.


Alan


Don't reply to this e-mail address - messages will be deleted unread. To reply to me take away the news and substitute alanc

 

[steve]

they are designed like this, i wouldnt use it as a secondry brake without
expecting the wheels to lock up, its simply a "parking brake" and should be
used as such, not applied until the vehicle is stationary, however its
perfect for handbrake turns, not that you should be doing them either.
the foreward and aft movement is just the shoes moving on the anchors,
i don't think you will find any printed document suggesting use of the
parking brake as an emergency brake on these vehicles, years ago it was
plausable, cars were lighter, they didnt drive as fast, and nobody was as
security and safety consious as they are nowadays.

It's not a slightly strange system - it is the norm nowadays for most
cars with rear discs.


Alan


Don't reply to this e-mail address - messages will be deleted unread. To

reply to me take away the news and substitute alanc

 

[Bob Smith]

they are designed like this, i wouldnt use it as a secondry brake without
expecting the wheels to lock up, its simply a "parking brake" and should be
used as such, not applied until the vehicle is stationary, however its
perfect for handbrake turns, not that you should be doing them either.

To do a handbrake turn, you should lock the wheels using the footbrake
first. Locking them at speed with the handbrake causes the components to
become detached, and rattle around in the drum.

Bob