Do you use the handbrakeon an auto?

Do you use the handbrake on an automatic?


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jimmy said:
It's a fact that autos suffer more from warped brake discs than manuals, the theory is that after a bit of spirited driving, the brake discs get hot, when at junctions, traffic lights etc holding the car on the foot brakes, the brake pads act as heat sinks and cool the brake discs unevenly.

Obviously this goes against cars with SBC and SBH like mine!!

As far as I understand it the most common problem in the circumstances you describe is that of brake pad material "imprinting" on the disc because the pads are clamped tight on to a very hot disc that stays that way for longer than the rest of the disc.

Once an area is imprinted more friction material can build up on top of that and the result can braking vibration often wrongly put down to a "warped" disc. Disc may still be flat but got a bit bumpy!

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml
 
BTB 500 said:
On any slope at all, yes I do use it. Holding back 2 tonnes of car must put some load on my (very expensive) transmission otherwise.

I was going to ask about this. Is there an issue with putting a load on the auto-box when parked with no parking brake on?
My C-class is the first auto I've owned so I'm no expert.

Slightly off topic: Is there an issue with holding the car on the footbrake in, for instance, a long queue with "D" still engaged? I seem to remember somebody warning me about doing this for long periods as it can affect the torque converter? It's probably pointles and uncomfortabel too but it's nice to know what effect it might have.
 
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C240Sport97 said:
do you mean use handbrake when you park the car or when you are stationary (say at traffic lights) waiting to go?

I meant both actually - had not thought to diffentriate
 
oilburner said:
Slightly off topic: Is there an issue with holding the car on the footbrake in, for instance, a long queue with "D" still engaged? I seem to remember somebody warning me about doing this for long periods as it can affect the torque converter? It's probably pointles and uncomfortabel too but it's nice to know what effect it might have.

Well, from a technical point of view, by holding an auto on the brakes with D engaged, the torque convertor will be pumping the fluid around, after extended periods this could overheat the fluid. But we all do it and I have never heard of any damage being attributed to this.

Personally, when in a jam, I shift to N if I dont think I am going to move for a few minutes or P if it looks like a bit longer.
 
Gollom said:
SBC means?

ttfn!
:bannana:

Sensotronic Brake Control. That's the Bosch fully powered brake system on all W211s up to the newly announced face lift as well as CLS/SL/CL. I'm suprised given the number of column inches devoted to the topic on this forum that you needed to ask. Of course you may now reply "Gotcha" because I bit at the bait on the end of your rod. :)

To answer your original question, I always use the parking brake when leaving the car or before putting the transmission in park. I'm with those who don't want two ton of car hanging on a single pawl.

In traffic jams I'd have to plead guilty to lighting up the sky with LED rear lights unless the holdup looks like a lengthy one.
 
jimmy said:
Well, from a technical point of view, by holding an auto on the brakes with D engaged, the torque convertor will be pumping the fluid around, after extended periods this could overheat the fluid. But we all do it and I have never heard of any damage being attributed to this.

Personally, when in a jam, I shift to N if I dont think I am going to move for a few minutes or P if it looks like a bit longer.

The other thing given the high price of fuel is you'll burn slightly more in Drive than you would in Neutral or Park as the engine is overcoming torque convertor drag to maintain tickover. When the price gets even higher selecting Neutral to save money will overcome the advantage of being able to creep forward with the traffic by lifting your foot of the brake as soon as the car in front moves forward.
 
jimmy said:
Well, from a technical point of view, by holding an auto on the brakes with D engaged, the torque convertor will be pumping the fluid around, after extended periods this could overheat the fluid. But we all do it and I have never heard of any damage being attributed to this.
However on this thread: Which gear at the lights? we learn that:
ROSPA said:
When stationary in traffic, even for many minutes, it is not necessary to move the gear lever into neutral because the torque converter absorbs the engine’s propulsion force but does not transmit it all to the gearbox. No wear is taking place. In fact, more wear will take place if you engage neutral then engage a drive gear when it is possible to move off. Most gearboxes will automatically select first gear when the vehicle becomes stationary.
 
Ha! It is RoSPA (or a RoSPA examiner, rather) who told me to put it in neutral in case I was shunted from behind. Clearly he was a rebel and speaking out of turn against the party line.

Even to this day, I bet he is always glancing over his shoulder, watching the shadows and sleeps with the doors and windows firmly locked. They are pretty unforgiving, the RoSPA policy makers.

Philip
 
Shude said:
However on this thread: Which gear at the lights? we learn that:Quote:
Originally Posted by ROSPA
When stationary in traffic, even for many minutes, it is not necessary to move the gear lever into neutral because the torque converter absorbs the engine’s propulsion force but does not transmit it all to the gearbox. No wear is taking place. In fact, more wear will take place if you engage neutral then engage a drive gear when it is possible to move off. Most gearboxes will automatically select first gear when the vehicle becomes stationary.

__________________

Looked at purely from a wear point of view, ROSPA is correct. In Drive at a standstill, the output side of the torque convertor is stalled and will apply a static force to the transmission brake bands. In neutral the transmission will rotate as all the brake bands are released. Mind you I'm not sure how many months you'd have to stay in that state to get any appreciable wear.

If the transmission oil cooler is correctly designed, the torque convertor should not overheat under stall conditions.
 
I have to say, my car (E320 CDi) creeps if you leave it in drive with the parking brake on (unless you ram the parking brake pedal to the floor), so I always put it into neutral at the same time as applying the parking brake.

Having been in a car when my brother accidently pressed the accelerator whilst delving in his pocket for change at a toll booth (car in Drive but handbrake applied) and have us shoot forward out of control and into the barrier arm, I am very cautious about leaving the car in Drive at any time that I don't actively want to be moving forward. At least it gave the French toll booth attendent a laugh.

Philip
 
prprandall51 said:
I bet he is always glancing over his shoulder, watching the shadows and sleeps with the doors and windows firmly locked. They are pretty unforgiving, the RoSPA policy makers.

Philip

Yeah, even in this weather. RoSPA need to get a life.
 
prprandall51 said:
Question for the technically minded (no, I don't know the answer! this is not more pedantry):

If you park your car by the roadside in a line of cars and use the P-Park position to hold the car but do not use the handbrake, and then some git comes along and shunts your car (good and hard, like they do) as they get into or out of the next parking space along, all of the energy of the impact will - I assume - be passed straight through the transmission to the transmission interlock that is the P-Park mechanism.

I wonder if you could damage an auto box in this way? Certainly, applying the hand brake would prevent this happening - or dramatically reduce the energy being transmitted, at least.

Any opinions?

Philip


Surely this is the reason autos can rock back & forward in P, to allow drivers to nudge cars either side and fit in small parking spaces?!
 
jdrrco said:
Surely this is the reason autos can rock back & forward in P, to allow drivers to nudge cars either side and fit in small parking spaces?!

...and (it therefore follows) why so many Americans drive automatics...
 
jdrrco said:
...and (it therefore follows) why so many Americans drive automatics...

It is a commonly held misconception that american cars rock gently because of the auto box.

The facility within american automobeeeeels to rock back and forth effortlesssly is the large blocks of jelly that are built into both the suspension system and also the drivetrain. This jelly, developed specifically for the US market by automotive supplier Chivers, is usually red in colour but on some cars is green.

A common "mod" in american tuning circles is to replace the lower wishbones with sponge fingers. This provides an even more impricise and sloppy ride, which is the ultimate aim of the US modders.:D
 
Hand brake? WTF is that :rolleyes: I guess I am lazy and the thought of changing another set of handbrake shoes sends shivers up my spine :crazy: :devil:
 
prprandall51 said:
is the large blocks of jelly that are built into both the suspension system and also the drivetrain. This jelly, developed specifically for the US market by automotive supplier Chivers, is usually red in colour but on some cars is green.

A common "mod" in american tuning circles is to replace the lower wishbones with sponge fingers. This provides an even more impricise and sloppy ride, which is the ultimate aim of the US modders.:D

So what colour is the jely in American presidents brains?
:D
 
Gollom said:
So what colour is the jely in American presidents brains?
:D

Totally colourless, how else would you explain their lack of imagination and misconception that everyone actually beleives anything they say?

Allan
 
I don't know how far good taste will allow me to go with this off-topic aspect to the thread, but I have just spoken to the R & D guys at Chivers and they said that the president's brain jelly was a special order in brown:confused:
 
Handbrake, what handbrake?

I'm in the only ever use the parking brake when on steep hills camp. Reason: if the autobox is in D it is all locked up with the TQ rotating, which is what it's designed to do. If the seletor is in N then the whole box will rotate so wear the components more als when the gear is re-engaged there will be a small amount of slip causing wear to the brake bands.

I don't believe there is any possibility of the parking pawl either wearing or breaking in use. They are a heavy duty pawl that goes round the serrated ring about a quater of the way round. The teeth are specially shaped so that the pawl will jump if there is any shock load such as towing, accident or putting in P at more than 5mph.

The parking mechanism is at the rear of the gearbox on the output shaft so no other parts are under load other than the engine and gearbox mountings.
 

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