Handbrake question!

[JamS3]

Probs a silly question but is the handbrake on the S3 in ANY way connected to the front brakes?

E.g lifting the handbrake leaver up and down will this do ANYTHING to the front brakes/calipers/pads??

Lastly when you put your handbrake on sometimes and after a second or so there is a big bang and the handbrake seems to drop lower to the floor when it appears to be set....what causes this?

Cheers

 

[madvw]

weird. The bang you describe sounds like when the handbrake is caught inbetween a click on the ratchet mechanism, or the ratchet mechanism is ********.

as for affecting the front brakes? I suppose it's not impossible for the pads to move a little closer to the disc when you pull the handbrake on, as i guess there would be a slight pressure generated from the compression of the rear pistons when the handbrake is pulled on. I wouldn't expect it to be enough to move the front pistons though...

 

[god_thats_quick]

Handbrake only acts on the rear calipers no link at ALL to the front.

Not a clue about the handbrake dropping to the floor but it's on a ratchet so there could be a problem with the actual lever.

 

[madvw]

[ QUOTE ]
Handbrake only acts on the rear calipers no link at ALL to the front.

[/ QUOTE ]

but if the front nearside caliper is on the same circuit as the rear offside caliper - could the pressure be enough to move the front hydraulically?

 

[god_thats_quick]

I didn't actually mean my post to sounds like a response to yours, I was just typing like a numptie and taking ages, I do however remember reading that the EBD on the S3 and the ABS / master cylinder setup at the front of the car prevents return pressure but also can apply each of the 4 brakes independantly so I don't think the situation you are describing can happen but it's a fair point. If I could be bothered I'd go check on elsawin as I remember looking at the braking system before doing the discs and pads.

 

[Ess_Three]

[ QUOTE ]
[ QUOTE ]
Handbrake only acts on the rear calipers no link at ALL to the front.

[/ QUOTE ]

but if the front nearside caliper is on the same circuit as the rear offside caliper - could the pressure be enough to move the front hydraulically?

[/ QUOTE ]

How?

The handbrake on the rear calliper is activated mechanically by a lever...not using the hydraulic fluid...it actually uses the self sdjusting ratchet mechanism...but I digress.

As you activate the lever, you don't pressurise the hydraulic fluid...so no link to the digaonally opposite calliper even if pressure could get through the ABS unit and master cylinder.

Technically, mechanically forcing the piston out *could* reduce the hydraulic pressure in the circuit...but since it's at no pressure anyway, this can be discounted.

 

[madvw]

[ QUOTE ]


How?



[/ QUOTE ]

I was never under the impression that the handbrake was a hydraulic one on road cars.

total theoretic thinking here - As the handbrake is applied via the cable, and the calipers are pulled towards the rear disk, they will force the pistons back into the calliper, hence the posibility of creating the hydraulic pressure on that circuit, causing the resulting action on the front pistons.

I know that it's unlikely (well, probably next to impossible), but can you see what i'm thinking? I know what i'm thinking, just explaining it poorly..

 

[Ess_Three]

[ QUOTE ]

total theoretic thinking here - As the handbrake is applied via the cable, and the calipers are pulled towards the rear disk, they will force the pistons back into the calliper, hence the posibility of creating the hydraulic pressure on that circuit, causing the resulting action on the front pistons.


[/ QUOTE ]

The rear calliper pretty much stays where it is...just centres up, as the piston is forced OUT towards the disc, on one side...and the disc is forced against the pad and hence other side of the sliding calliper on the other.

So as the handbrake cable is pulled, the lever forces the piston OUT...technically reducing any hydraulic pressure within the calliper body.
Do you follow? not sure if I've explained that well...

 

[madvw]

Crystal now, cheers. For some reason i was under the impresion that the caliper "squeezed" the pads together last night... wel it seemed to make sense at the time /ubbthreads/images/graemlins/wink.gif Dont know why, as I've never seen hinged carriers...

 

[benk]

I thought there had been mention that slightly lifting the handbrake causes the haldex to disable (I assume this disengagement is something controlled by the ECU)? Just wondered if that is anything to do with the "bang".

The only bangs I have heard on my cars when stationary have been when the pads have seized onto the discs (e.g. after washing the car and pads have dried onto discs), and lowering the handbrake doesn't free the car, so you might have to jump about in the seat a bit to get them to free themselves - the bang being heard as they pop off the discs again.

Maybe you're getting something related, like you've engaged the handbrake, and when you release the brake pedal, the car slips a little as the front discs are released (are you parking on a hill?)

 

[god_thats_quick]

[ QUOTE ]
I thought there had been mention that slightly lifting the handbrake causes the haldex to disable (I assume this disengagement is something controlled by the ECU)?

[/ QUOTE ]

Only on cars with ESP, on those without the handbrake has nothing to do with Haldex neither does the brake pedal so you can also heal and toe if you can get your foot to bend right.