What is my handbrake for ?

[219]

I have a 2012 SLK55. It also says this and automatically releases when taken out of Park, so I never use the push/pull handle to the right for the handbrake.

In a friend's 2016 GLA220d, it has a stalk gear lever and the same push/pull handle for the handbrake. In her car, you have to manually apply and release the handbrake.

It is somewhat illogical if you had a separate control for the parking brake if it applied and released automatically.

The only circumstance I can think of is to satisfy the law which requires a separate braking system with separate means of actuation for the eventuality of complete brake failure .

However , no one has thus far answered my earlier question as to whether the electric parking brake will even work when the car is in motion , far less whether it would actually stop the car in an emergency ? The only comment so far was ‘there is a button’ .

There is also the further question re brakes on the newer cars - do they still have separate drums for the parking brake , or are they now relying on the disc brakes ?

It is well known that disc brakes are not suitable for parking brakes ( hence Mercedes for decades have always had separate drums , along with BMW , Volvo and other well engineered cars ) : the reason being that if the parking brake is applied against a hot disc , then as the disc cools and contracts the grip will relax and the car can roll away if only relying on the parking brake . I actually saw this once ( extremely bad timing , when I returned to my car after being parked for some time on a steep hill in Glasgow - before I could start my car and move off , the car in front just slowly started to roll back onto my front bumper ! I waited until my meter was about to expire , with no sign of the return of the other driver , and called the police . Two cops came round , and must have obtained the other drivers details . The driver arrived some minutes later , blustering that his handbrake was applied fully - indeed the lever between the seats was almost vertical - but it had failed . I asked him in front of the cops if he had an idea his handbrake wasn’t up to standard why hadn’t he parked in gear and/or turned his wheels to block against the kerb . The cops told me they would deal with him and got him to move his car forward so I could get out . One of them had his pad out , so he was at least getting a HO/RT1 ) .

On the other hand , if a parking brake uses drums , then as the drum cools , the grip tightens .

Hence discs are good for slowing down and stopping , but drums are best for holding .

It would not surprise me in the least if this has been forgotten in some new ‘made to a price’ cars .

 

[219]

Yes me too, just like white goods, I find myself keeping my old stuff for longer and just getting stuff repaired because you know the parts are engineered to be repairable as opposed to the throw-away society which everything nowadays is manufactured to.

Well, credit to Mercedes if they've changed a plastic housing back to a metal one because it melts. VW family continue to use plastic water impellers which melt - I guess they see this as after-service income stream: save money on parts at manufacture, make more money downstream on repairs, it's a fair business model.

Perhaps it is the same with VW , currently have MkV and MkVI Golfs , plus a Polo 9N in the family - all trouble free , and have had VWs all the way from air cooled in the early 60s to date , with the only failures I can recall being a cracked Dizzy cap on one Beetle and a blown CHG on my 1976 Audi 100GL .

 

[leef44]

It is somewhat illogical if you had a separate control for the parking brake if it applied and released automatically.

The only circumstance I can think of is to satisfy the law which requires a separate braking system with separate means of actuation for the eventuality of complete brake failure .

However , no one has thus far answered my earlier question as to whether the electric parking brake will even work when the car is in motion , far less whether it would actually stop the car in an emergency ? The only comment so far was ‘there is a button’ .

There is also the further question re brakes on the newer cars - do they still have separate drums for the parking brake , or are they now relying on the disc brakes ?

It is well known that disc brakes are not suitable for parking brakes ( hence Mercedes for decades have always had separate drums , along with BMW , Volvo and other well engineered cars ) : the reason being that if the parking brake is applied against a hot disc , then as the disc cools and contracts the grip will relax and the car can roll away if only relying on the parking brake . I actually saw this once ( extremely bad timing , when I returned to my car after being parked for some time on a steep hill in Glasgow - before I could start my car and move off , the car in front just slowly started to roll back onto my front bumper ! I waited until my meter was about to expire , with no sign of the return of the other driver , and called the police . Two cops came round , and must have obtained the other drivers details . The driver arrived some minutes later , blustering that his handbrake was applied fully - indeed the lever between the seats was almost vertical - but it had failed . I asked him in front of the cops if he had an idea his handbrake wasn’t up to standard why hadn’t he parked in gear and/or turned his wheels to block against the kerb . The cops told me they would deal with him and got him to move his car forward so I could get out . One of them had his pad out , so he was at least getting a HO/RT1 ) .

On the other hand , if a parking brake uses drums , then as the drum cools , the grip tightens .

Hence discs are good for slowing down and stopping , but drums are best for holding .

It would not surprise me in the least if this has been forgotten in some new ‘made to a price’ cars .

Unfortunately, your suspicions are correct. I drove my friend's GLA and as I was driving off, she told me that I needed to manually release the handbrake. I didn't notice the handbrake light symbol had not extinguished on the dash. The car drove away quite happily.

 

[flowrider]

Unfortunately, your suspicions are correct. I drove my friend's GLA and as I was driving off, she told me that I needed to manually release the handbrake. I didn't notice the handbrake light symbol had not extinguished on the dash. The car drove away quite happily.

In my SL if I leave the handbrake engaged and attempt to drive off I get a warning beep the dash lights up.

 

[Deleted member 149005]

Are we confusing electric parking brakes and auto parking brakes?

My SLK has a lever (lower dashboard) but uses motors to operate an (electronic) parking brake...

 

[219]

Are we confusing electric parking brakes and auto parking brakes?

My SLK has a lever (lower dashboard) but uses motors to operate an (electronic) parking brake...

Possibly , but both will be electrically actuated , just that in some implementations they may be automatically applied and released as well .

I would imagine the foot brake hold feature , for use at lights or in queues , may be via some sort of non return valve in the hydraulic circuit , and downstream of the brake light switch so brake lights go off when pedal is released , and with some method of release ( solenoid ? ) linked to throttle opening ?

 

[leef44]

Are we confusing electric parking brakes and auto parking brakes?

My SLK has a lever (lower dashboard) but uses motors to operate an (electronic) parking brake...

Now I'm confused, please elaborate.

What is the difference? Is it the way they turn on/off or are they completely different brake parts?

I can't say I've paid too much attention to this but wonder if I've been doing it wrong all this time.

 

[Deleted member 6183]

It is somewhat illogical if you had a separate control for the parking brake if it applied and released automatically.

The only circumstance I can think of is to satisfy the law which requires a separate braking system with separate means of actuation for the eventuality of complete brake failure .

However , no one has thus far answered my earlier question as to whether the electric parking brake will even work when the car is in motion , far less whether it would actually stop the car in an emergency ? The only comment so far was ‘there is a button’ .

I did answer more fully but he has me on ignore.

How funny is that?

 

[ToeKnee]

From my instructions regarding using electric brake to stop vehicle: -
Emergency braking
The vehicle can also be braked during an emergency by using the electric parking brake.

While driving, push handle

of the electric parking brake.
Info

The vehicle is braked for as long as the handle of the electric parking brake is pressed. The longer the electric parking brake handle is depressed, the greater the braking force.
During braking:

• a warning tone sounds
• the Release park. brake message appears
• the red
  
  indicator lamp in the instrument cluster flashes

When the vehicle has been braked to a standstill, the electric parking brake is applied.

My electric park brake doesn't come on automatically, I have to physically press the lever but it will come off automatically if I put the car in drive and accelerate away.

 

[Deleted member 6183]

From my instructions regarding using electric brake to stop vehicle: -
Emergency braking
The vehicle can also be braked during an emergency by using the electric parking brake.

While driving, push handle

of the electric parking brake.
Info

The vehicle is braked for as long as the handle of the electric parking brake is pressed. The longer the electric parking brake handle is depressed, the greater the braking force.
During braking:

• a warning tone sounds
• the Release park. brake message appears
• the red
  
  indicator lamp in the instrument cluster flashes

When the vehicle has been braked to a standstill, the electric parking brake is applied.

My electric park brake doesn't come on automatically, I have to physically press the lever but it will come off automatically if I put the car in drive and accelerate away.

So, there’s a button then

 

[clk320x]

Have you actually passed a test of competence to drive ?

This question illustrates perfectly the argument for ongoing retests .

OP may have done his test in an automatic in which case he wouldn’t have needed to use the ‘handbrake’...

 

[Deleted member 149005]

OP may have done his test in an automatic in which case he wouldn’t have needed to use the ‘handbrake’...

He would have failed if he didn't use his handbrake...

 

[clk320x]

He would have failed if he didn't use his handbrake...

Wow, there’s really nothing you’re not an expert on.

 

[219]

OP may have done his test in an automatic in which case he wouldn’t have needed to use the ‘handbrake’...

You still , for the purposes of the driving test , have to use the hand/parking brake when coming to a halt , it is a fault not to . This is regardless of manual/automatic .

I used to fail people on advanced tests if they failed to use it . If you wanted a class 1 pass you even had to apply it between stopping and selecting reverse , before parking . These were the guidelines .

It is also illegal to leave the vehicle without ‘setting the brake’ .

 

[Pilko14]

Besides driving apparently. Theres no requirement to use a handbrake on your driving test.

 

[219]

Besides driving apparently. Theres no requirement to use a handbrake on your driving test.

Which old sweetie wife told you that ?

She was WRONG .

 

[Pilko14]

Which old sweetie wife told you that ?

She was WRONG .

Really, so are most driving instructors then.

 

[219]

Really, so are most driving instructors then.

Many of them have no clue .

I see so many now teaching students to trafficate right on approach to roundabouts at which they are going straight ahead . They live in a world of their own .

I am ex police advanced instructor , current emergency response driver , ex IAM and LSD advanced instructor .

I know better .

When stopping , whether on a hill , or at lights , or in traffic , the parking brake MUST be applied .

If you leave the vehicle without doing so that is a specific offence .

 

[Pilko14]

Many of them have no clue .

I see so many now teaching students to trafficate right on approach to roundabouts at which they are going straight ahead . They live in a world of their own .

I am ex police advanced instructor , current emergency response driver , ex IAM and LSD advanced instructor .

I know better .

Of course you do, that was never in doubt!!

 

[Deleted member 6183]

Which old sweetie wife told you that ?

She was WRONG .

What's an old sweetie wife?