How to drive an auto?

[SLinKyjoe]

grow up and behave like an adult

definition of Adult:

Big Kid who has forgot how to have fun! = boring old ****.

 

[Tony]

The problem is probably material transfer from pad to disc or vice-versa rather than warped discs, which is highly unlikely with ventilated discs.

Quite possibly the problem is misdiagnosed and it actually is material transfer from pad to disc. The symptom is the same though and it seems, from the description in the link you provided, that it's most likely to happen when the car is held stationary on the foot brake.

 

[television]

Having read the complete link provided, some aspects and things mentioned behave otherwise in engineering.

Hard material cast iron disc does not wear the softer pad, its the other way around.
A steel shaft rotating in a bronze bearing will wear the shaft before it wears the bearing. this was always the case in dynamos and fans, even in very low speed devices such as king pins, the pin always went before the bush, on a ratio of 3 to1.
Brake pads have a surface area of 1/4 of the disc. Working on the asumption that the pads are changed at 20k and that the disc can need replacement from 40k up, this would show that the Disc wears more than the pad, or the harder material wears first.
I am not a scientist, but I have had a lot experience in cast iron products.
The biggest cause of warping in cast iron is uneven heating or cooling. Many of us have all had our cylinder heads warp at some point in life, mainly caused be poor cooling or boiling the system.before any attemt to weld these things the head had to be warmed to 400c, even then a good result could not be guaranteed owing to differences in the heat applied. The only 100% remedy was to repair using the metal lock technoligy.
Back to brake disc, in you do a high speed stop and then leave the foot brake applied, this will cool a part of the disc before the rest of the disc owing to the heat sink action, provided by the calliper causing uneven cooling of the disc.
Most disc warp only after a hard stop, and this is neally always the case, don't hold the car on the footbrake for a while. leave them to cool a while.
In normal driving in town, the heat genarated is too low to warp them, and 90% of auto drivers stop at traffic with the foot brake applied and never have a problem. I think that I have only ever replaced 4 disc in the hundreds of cars that I have owned.

Malcolm

 

[Silver Arrow]

I think that I have only ever replaced 4 disc in the hundreds of cars that I have owned.

Malcolm

Ummm. My wife's old 240 Volvo estate is manual, and she says that the is the only sane driver in the family, but that has gone through two sets of discs in the last two years. We have had it from new (1989) and the earlier sets lasted several years. I have gone through 1 set in my XJS but it don't get that much use. On the second set in the Quattro, (Manual, but lots of Extra Sensory Perception which takes over everything). Coupe seems OK, but the rears need a polish occasionally if it hasn't been out for a bit. Lotus calipers stick if left in the garage overnight!

 

[television]

I think that I have only ever replaced 4 disc in the hundreds of cars that I have owned.

Malcolm

Ummm. My wife's old 240 Volvo estate is manual, and she says that the is the only sane driver in the family, but that has gone through two sets of discs in the last two years. We have had it from new (1989) and the earlier sets lasted several years. I have gone through 1 set in my XJS but it don't get that much use. On the second set in the Quattro, (Manual, but lots of Extra Sensory Perception which takes over everything). Coupe seems OK, but the rears need a polish occasionally if it hasn't been out for a bit. Lotus calipers stick if left in the garage overnight!

Are the xjs inboard like the XJ6, I had one break on mine, makes you stop quick.

Living in Sweden in the winter with the salt plays hell with the rears, always having to do hard braking to clean them up,not easy when its icy.
One of the rears on my V70R split when I left it for three weeks at Stansted after driving there on salty roads.

malcolm

 

[Silver Arrow]

Are the xjs inboard like the XJ6,
Yup, sure are! They are a pig to deal with. The handbrake pads are abominable.

 

[Blobcat]

D, parking brake on, footbrake covered and used to warn approaching traffic from the rear. Except when we could see we'd be there for ever, when N, or engine off would be more appropriate.
or was that just me?

Agreed, I don't use 'P' unless I'm parking as the reversing lights flashing on when going through the gate confuses those behind.

 

[mike65]

I never thought of that!

Mike.

 

[television]

I never thought of that!

Mike.

Handy things forums.so many veiws and thoughts

malcolm

 

[wireman]

Some of the above advice is attrocious.
Try reading some books about driving properly and you will be told that the vehicle should be in neutral with the parking brakes engaged fully.
Holding the car on the service brakes (regardless of how strongly) is foolhardy, when some errant and inattentive driver collides with the rear of your vehicle you the driver will stand still momentarily while the rest of the vehicle including its footbrake pedal will move suficiently forward to release the brakes fully......You cannae change the laws o' physics
Queing at a junction with the brake lights lit is an offence under the road vehicle lighting regulations "Causing dazzle" is the term, which also applies to fog lights not being used as they should be i.e. in real fog.
Not using the correct and safest process is responsible for a huge amount of the damage and injury which occurs in minor shunts.
Maybe holding the brake pedal to illuminate the stop lamps is a good idea whilst another vehicle is approaching to join behind you in a que but it would be good manners to extinguish the lights once you are certain that they have stopped behind you.
I always, as you may have guessed endeavour to apply the parking brake if the stop will be extended to greater than a few seconds, Yes occasionaly this delays my getaway by a fraction of a second but who cares?
In my experience never moving the hand brake except for the MOT is not clever since the linkages are all going to be cruded up and inefficient thus requiring servicing or repair and expense, not moving the gear selector because it might wear out is about the most feeble excuse for being as tight as a gnats chuff that I have ever read.
We all seem to be in possesion of good nice motor cars so perhaps we could all indulge in good nice driving.
Please don't be the third motorist to smash into my rear, the other two guys who did were also stopped both without their parking brakes applied when they were hit from behind and we all got hurt and my injuries persist to today.
If you are hit hard from behind and your auto box is in drive how are you going to stop you car whislt recovering your posture and orientation?
Remember the vast majority of road incidents are caused by the nut that holds the steering wheel.
Lots of usefull advice can be gleaned from people like ROSPA and the IAM, people who I freely admit are much more qualified to comment than I.

 

[CMR]

Pull up at traffic lights (anticipating a long wait). Use the handbrake (well, footbrake - but you know what I mean!).
Should I leave the car in 'Drive', or move it to 'Neutral' or 'Park'?

Coming from driving a manual, the combination of handbrake and 'drive' doesn't seem all that healthy. But I've read elsewhere that moving from D to N/P causes unnecessary wear on the linkage, and in some cases can cause extra wear on the box - due to oil not getting circulated properly.

C240 is my first auto as I've always driven manual cars. So if I'm at lights or stopped for a while in a queue I have been putting it in Neutral as you would with a car with gears (sometimes with footbrake if neccessary (not handbrake). Holding an auto in drive with the footbreak equates to riding the clutch on a gear car (like you may do on a hill in slow moving traffic) but is often advised against due to wear on the clutch. I don't know enough of the mechanics of an auto if this is the same kind of thing so should I not use neutral at all and just hold it in Drive with the footbrake? Which method causes most wear?

 

[jberks]

C240 is my first auto as I've always driven manual cars. So if I'm at lights or stopped for a while in a queue I have been putting it in Neutral as you would with a car with gears (sometimes with footbrake if neccessary (not handbrake). Holding an auto in drive with the footbreak equates to riding the clutch on a gear car (like you may do on a hill in slow moving traffic) but is often advised against due to wear on the clutch. I don't know enough of the mechanics of an auto if this is the same kind of thing so should I not use neutral at all and just hold it in Drive with the footbrake? Which method causes most wear?

Common misunderstanding.
The clutch on a manual is a physical friction plate that wears, together with a release bearing that also wears. These are designed to handle short use periods for gearchanges, hence you don't hold the clutch too long. An auto has a fluid (oil filled) clutch - called the torque converter. This doesn't actually wear. Allegedly it will heat up over time, but normally we are talking about 1-2 light changes and it takes far longer than that.
Switching from D to N, causes various changes in the gearbox which don't take place if you stay in D, hence the more you do it, the higher the wear.
So, foot on the foot brake and just wait, (e.g. do nothing) is the least wearing way to do it on an auto.

 

[hawk20]

Some of the above advice is attrocious.
Try reading some books about driving properly and you will be told that the vehicle should be in neutral with the parking brakes engaged fully.
.

Try reading some better books including Merc handbooks and you will be told that automatic cars (like nearly all Mercs) should be in 'P' not in neutral and -as you say- with the parking brake on if the stop is more than brief.

 

[jberks]

Holding the car on the service brakes (regardless of how strongly) is foolhardy, when some errant and inattentive driver collides with the rear of your vehicle you the driver will stand still momentarily while the rest of the vehicle including its footbrake pedal will move suficiently forward to release the brakes fully......You cannae change the laws o' physics
Queing at a junction with the brake lights lit is an offence under the road vehicle lighting regulations "Causing dazzle" is the term, which also applies to fog lights not being used as they should be i.e. in real fog.
Not using the correct and safest process is responsible for a huge amount of the damage and injury which occurs in minor shunts.
Maybe holding the brake pedal to illuminate the stop lamps is a good idea whilst another vehicle is approaching to join behind you in a que but it would be good manners to extinguish the lights once you are certain that they have stopped behind you.
I always, as you may have guessed endeavour to apply the parking brake if the stop will be extended to greater than a few seconds, Yes occasionaly this delays my getaway by a fraction of a second but who cares?
In my experience never moving the hand brake except for the MOT is not clever since the linkages are all going to be cruded up and inefficient thus requiring servicing or repair and expense, not moving the gear selector because it might wear out is about the most feeble excuse for being as tight as a gnats chuff that I have ever read.
We all seem to be in possesion of good nice motor cars so perhaps we could all indulge in good nice driving.

I don't see it.

Whenever stationary with no one behind me, I keep one eye on my rear view mirror. Hence when I was last rear ended, I was ready for it and the foot brake remained firmly applied. I am even able, as I did on one occasion, to quickly ease off the pedal and as it was in D, roll forward a few feet, allowing the poor muppet more chance to stop, which he did, 1'' off my bumper. No such flexibility with a handbrake and neutral. I would in fact turn it around. When stationary and not surrounded by stationary traffic, you should be observing what is happening around you and therefore never be in a shunt you weren't expecting.

Anyway, given that one end of the pedal is connected to the floorpan, whilst the other, via my foot and leg are connected to the seat backrest which is, in turn, also connected to the floorpan, the seat, me and the pedal will all move in unison, hence I can't see why a rear end shunt would lead me to release the pedal. Ok, If I had the seat badly adjusted and was slouching, perhaps I could slide on the seat, but this is down to an unsafe driving poisition, not physics.

Also, the 'handbrake' is 10% of the efficiency of the hydraulically if not SBC assisted footbrake. A car gently rear ended in neutral with the handbrake on will roll straight past the handbrake. It is well beyond most handbrakes to cope with any shunt. A car held with the footbrake will need to be hit hard enough to break the tyres traction, even if you do back off the pedal slightly. If you refer to your foot coming off the pedal, then again, I would say you woeren't in full control in the frist place as your foot should be in a secure location.

Also, if I'm sitting with the footbrake on and then release it to apply the handbrake, up comming traffic, may misread that for me starting to move off and not slow down appropriately.

Many years ago, I followed some traffic on the M1 near Luton. The guy in front, in true SE fashion was stuck to the bumper in front (at over 80mph) and his brake lights were on and off constantly. I backed off, fearing a collision and when I finally came across him again I saw the brake lights come on and go off as usual. From the distance and with the curve of the road, all I could tell was that I was gaining on him a little - reasonable given that he had been slowing and speeding up constantly. So I backed off and covered the brake, but initially didn't press it, figuring that he was accelerating and our speeds would match very shortly. What I didn't know was that he had stopped, put on his handbrake and dropped it into neutral. I learned 2 things that day. 1) Unladen transit vans don't stop in anything like the highway code distances and 2) whenever stopped, use brake lights and if necessary hazards to warn traffic behind.

In terms of dazzle, as discussed before, it's easy to look away, plus the sudden absense of dazzle then tells all cars behind that we're moving off again.

I agree on the fog lights though. One of my pet hates!

 

[SLinKyjoe]

here is some advice from an expert.

you may wish to read down the page a bit

http://www.telegraph.co.uk/motoring/main.jhtml?xml=/motoring/2001/02/13/emrip13.xml
http://www.telegraph.co.uk/motoring/main.jhtml?xml=/motoring/2000/12/12/emrip12.xml
http://www.iam-bristol.org.uk/articles/An Observing Guide.pdf
http://www.donpalmer.co.uk/handbook/part1.htm
http://www.ineeddrivinglessons.co.uk/latestnews.php

 

[hawk20]

here is some advice from an expert.

you may wish to read down the page a bit

http://www.telegraph.co.uk/motoring/main.jhtml?xml=/motoring/2001/02/13/emrip13.xml
http://www.telegraph.co.uk/motoring/main.jhtml?xml=/motoring/2000/12/12/emrip12.xml
http://www.iam-bristol.org.uk/articles/An Observing Guide.pdf
http://www.donpalmer.co.uk/handbook/part1.htm
http://www.ineeddrivinglessons.co.uk/latestnews.php

A lot of his advice is appallingly wrong in my view. Here is a sample:-
"Should you find yourself travelling downhill on ice, do not use the brakes; drive towards the kerb at a shallow angle and use the kerbstones to slow you down. You may have to renew a wheel and perhaps a tyre, but that is preferable to a life-threatening accident".

IMO that is lunatic advice. Most cars nowadays have ABS brakes which work perfectly well on ice. Trying to stop a 2 ton car by nudging the kerb at any appreciable speed is like trying to stop a tanker with a rowing boat.

On wear of Auto boxes in drive he clearly hasn't read JBerks posting number 72 here.

Back to traffic lights, I disagree with him again. Stick the car in P if you are stopping a while, and put on the parking brake. That is the correct way. And if it is going to be some while like at a level crossing, then turn off the engine. That way you won't be pumping unnecessary fumes into the car behind or the air we breathe.

On another point, I have checked on my car and going from D to P does not put on the reversing lights as some have argued.

 

[Blobcat]

Are your reversing lights working?......

 

[hawk20]

Are your reversing lights working?......

Yes perfectly. But when sliding rapidly from D to P they do not come on. We checked this very evening. Only if you go very slowly.

 

[Blobcat]

what about from P to D?

 

[jberks]

what about from P to D?

I haven't checked but I believe Hawk is right on the reversing lights issue. The box is electronically controlled so there is no longer a mechanical reason that it has to pass through R at all. If you flick it into D, the computer should be smart enough to recognise what you are doing and go straight to D. This would certainly explain the slight delay when selecting R as it waits mometarily to see if your staying there.
The old 4speed mechanical units may go to D via R but I suspect the tip shift 5 speed boxes and the 7 speed units don't anymore.

On the 'formal advice' stuff. It's rather like all the nanny state warnings you get these days. They have to give you advice based on the idea that you are incompetent and your car has cross ply tyres, drum brakes which don't work very well and your suspension has seen better days. If they give you realistic advice, then they'll get sued by someone who does fit that scenario.
It's rather like the whole stopping distance on the highway code. We all know that an ESP equipped Merc will stop in a fraction of that stated. In fact, I watched some prog or other where they put an S class up against an elise or something on a swerve and stop test. Despite being twice as heavy, the S class blitzed the elise due to the ESP and both were well within the official distances.
As you say, stopping by running into the kerb in an ABS equipped car is just plain daft and I imagine that the ABS will stop you far more quickly than the friction caused by sliding down the kerb, especially in something as heavy as a merc.

Finally, what is the advice on an SBC stop equipped car? Are they saying that you should use a handbrake, or even P which locks only the back wheels, when the SBC stop will apply automatically controlled pressure to all 4 wheels, ensuring that they don't move an inch.