On 25/06/2018 10:35, Dave Plowman (News) wrote:


Seems lots on here can't understand the concept of one wheel running at
different RPM from the others. Perhaps they only ever drive in a straight
line.



An interesting thing related to this: if you have a DSG-equipped VAG
car, and it starts refusing to change up gears (but will do it if you
use the lever to tell it to change up), it's an ABS sensor failing. It
generally won't trigger an fault code for a while. It's done that way so
it won't auto-change up half way around a corner, apparently.

http://www.piglet-net.net/pigblog/?p=2463

Chris Bartram wrote:

if you have a DSG-equipped VAG car, and it starts refusing to change up
gears

I'm on my second such car, but have not experienced that issue, the
reason for the last one going was that the gearbox was getting "fussy" ...

In article ,
Chris Bartram wrote:
On 25/06/2018 10:35, Dave Plowman (News) wrote:


Seems lots on here can't understand the concept of one wheel running at
different RPM from the others. Perhaps they only ever drive in a straight
line.



An interesting thing related to this: if you have a DSG-equipped VAG
car, and it starts refusing to change up gears (but will do it if you
use the lever to tell it to change up), it's an ABS sensor failing. It
generally won't trigger an fault code for a while. It's done that way so
it won't auto-change up half way around a corner, apparently.

http://www.piglet-net.net/pigblog/?p=2463

Interesting. Just got a car with a similar box which they call PDK (twin
clutch) And it is superb. At low speeds (as in round town) it just seems
to get into as high a gear as possible very quickly. Regardless if the
road is straight or not.

I'll have to take note when driving at higher speeds - although I'd expect
an ABS sensor throwing up irregular pulses to generate a fault code

--
* I like you. You remind me of when I was young and stupid

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Andy Burns wrote:
Chris Bartram wrote:

if you have a DSG-equipped VAG car, and it starts refusing to change up
gears

I'm on my second such car, but have not experienced that issue, the
reason for the last one going was that the gearbox was getting "fussy"

Did wonder what the expected life of these boxes is compared to a
conventional auto.

Was on a London single decker bus the other day that appeared to have an
SMG type auto, and that crunched when changing up into what I think was
third gear. Like you get with worn synchromesh.

--
*You know you're a redneck if your home has wheels and your car doesn't.

Dave Plowman London SW
To e-mail, change noise into sound.

"Andy Burns" wrote in message
...
Chris Bartram wrote:

if you have a DSG-equipped VAG car, and it starts refusing to change up
gears

I'm on my second such car, but have not experienced that issue, the reason
for the last one going was that the gearbox was getting "fussy" ...

Do people tend to use DSG-equipped cars in auto or manual mode mainly, I
wonder? I have always found that the big problem with automatics is that
they change down at the wrong time, eg during acceleration, especially when
half-way round a corner or when accelerating out of a roundabout. A
transmission that makes gearchanges more seamless while still allowing the
driver to choose when to change gear (eg during brief gaps in acceleration
when the change is less noticeable) sounds great. I think I'd tend to use it
in automated-manual mode - the best of both worlds - rather than letting the
transmission choose when to change.

Some time I'll have to test drive a VW with DSG and see how easy it is to
drive compared with a) a fully manual gearbox, and b) a
planetary-gear/torque-converter automatic box. At least modern VWs don't
suffer from the problem that (I think) the Mark V Golf TDI had, where the
engine was notoriously easy to stall - rather than being almost stall-proof,
as most diesels are, it seemed to stall even more easily than a petrol. That
Golf is the only car (petrol or diesel) that I have repeatedly stalled when
setting off on a test drive - and the salesman said I was not alone. It's
almost as if the ECU detects that there is insufficient fuel and therefore
insufficient engine torque to be able to accelerate the car so it
deliberately cuts the fuel altogether rather than letting the engine labour
slightly to give the driver chance to increase the throttle a bit. I imagine
that if you drive the car all the time, you soon get used to it, but for
occasional drivers it catches you out.

How easily do people find it is to control the speed accurately at very slow
speed (eg when manoeuvring or when crawling forward in a queue of traffic).
It may be that I've never developed the muscle memory to be able to control
a car's speed solely on the accelerator, when in a manual car I tend to
control the speed also with the clutch, with a more constant engine speed.
For me, the best combination would be a DSG that had a clutch pedal that was
only used for finer control of speed for very slow manoeuvring and which was
not used for gear changes. With a (conventional) automatic, I'm always
scared stiff, especially if the accelerator pedal/linkage sticks slightly as
the car gets older, of the accelerator pedal moving suddenly and the car
surging forwards. When I have driven automatics occasionally (eg as hire
cars on business journeys) I've been very aware of this possibility when
reversing out of a parking space and the need to release the accelerator
and/or touch the footbrake the instant that I detect it happening - a reflex
which I bet elderly drivers who drive into shop fronts haven't got. It's the
only time that I left-foot-brake: as a precaution when inching
forwards/backwards in a car with no manual clutch.

On 26/06/2018 13:43, Andy Burns wrote:
Chris Bartram wrote:

if you have a DSG-equipped VAG car, and it starts refusing to change
up gears

I'm on my second such car, but have not experienced that issue, the
reason for the last one going was that the gearbox was getting "fussy" ...
It *did* make me a bit nervous, but Tim Downie on here somewhere had had
the same. The Leon was approaching 140k when I sold it.

Dave Plowman wrote:

Andy Burns wrote:

the gearbox was getting "fussy"

Did wonder what the expected life of these boxes is compared to a
conventional auto.

My first one was 'chauffeur smooth' for a year, then as good as a decent
driver with a manual for 3-4 years, very enjoyable.

Then, on cold mornings, it sometimes gave a bit of a thump in your back
the first time it came to a halt as it was changing down into 1st, as
though it wasn't sure of the bite point, I had it recalibrated at next
service it was better for 6 months then started doing the same again, it
then occasionally put the gearbox into "limp mode" for few seconds after
long journeys on hot days, only ever a warning, not an error. Main
dealer option at that point was a "DSG rebuild kit", not cheap, and not
much guarantee.

OBD cable showed it was occasionally unhappy with pressures and
temperatures of hydraulic clutch valves, so it got chopped in, maybe
I'll resist using the launch control on this one :-)

Was on a London single decker bus the other day that appeared to have an
SMG type auto, and that crunched when changing up into what I think was
third gear. Like you get with worn synchromesh.

I thought they were pre-selector boxes?

In article ,
NY wrote:
Do people tend to use DSG-equipped cars in auto or manual mode mainly, I
wonder? I have always found that the big problem with automatics is that
they change down at the wrong time, eg during acceleration, especially
when half-way round a corner or when accelerating out of a roundabout.

Any auto only changes down if the speed is too low, or you demand extra
acceleration from it. If you are driving so fast on a slippery surface
that a gearchange mid corner is going to cause problems, then it would
make sense to select the gear you want before. But most modern boxes will
learn when you're pressing on and stay in a low gear much longer than when
driving normally.

A
transmission that makes gearchanges more seamless while still allowing
the driver to choose when to change gear (eg during brief gaps in
acceleration when the change is less noticeable) sounds great. I think
I'd tend to use it in automated-manual mode - the best of both worlds -
rather than letting the transmission choose when to change.

On a twin clutch DSG box, there is effectively no interruption of power
flow when it changes gear. Far far less so than with a manual box.

Modern autos are so good there is usually no need to use the manual
function. Except for fun.

--
*My dog can lick anyone

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman wrote:

On a twin clutch DSG box, there is effectively no interruption of power
flow when it changes gear. Far far less so than with a manual box.

The only time you notice is if you 'confuse it' e.g. it's in 4th and
preparing to change up to 5th, but you boot it so then it needs to find
3rd in a hurry.

Modern autos are so good there is usually no need to use the manual
function. Except for fun.

no disagreement there :-P

On 26/06/18 09:48, Robin wrote:
On 26/06/2018 09:06, The Natural Philosopher wrote:
On 26/06/18 06:31, Richard wrote:

20P and 50P coins have a constant diameter despite not being circular.

No, they do not.


They do for the normal meaning of "diameter" (which is not confined
circles, spheres or other n-spheres)


yes it is.




--
Of what good are dead warriors? €¦ Warriors are those who desire battle
more than peace. Those who seek battle despite peace. Those who thump
their spears on the ground and talk of honor. Those who leap high the
battle dance and dream of glory €¦ The good of dead warriors, Mother, is
that they are dead.
Sheri S Tepper: The Awakeners.

On 26/06/18 10:45, NY wrote:
I think the only important thing is the the distance between the axle
and the point which touches the ground ("the effective radius", as some
people have called it) is constant as the tyre rotates - as indeed it
must be, otherwise you'd have a very bumpy ride :-) The radius at all
other points on the tyre which are not touching the ground is not
important.

100% wrong in every respect.


--
Theres a mighty big difference between good, sound reasons and reasons
that sound good.

Burton Hillis (William Vaughn, American columnist)

On 26/06/2018 16:42, The Natural Philosopher wrote:
On 26/06/18 09:48, Robin wrote:
On 26/06/2018 09:06, The Natural Philosopher wrote:
On 26/06/18 06:31, Richard wrote:

20P and 50P coins have a constant diameter despite not being circular.

No, they do not.


They do for the normal meaning of "diameter" (which is not confined
circles, spheres or other n-spheres)


yes it is.


It would be nice if you would just this once back up your claims with
some evidence that you are right and everyone from the OED to the Royal
Mint are wrong.

--
Robin
reply-to address is (intended to be) valid

On Tue, 26 Jun 2018 10:40:41 +0100, "NY" wrote:

snip

I had never realised that the flats on a 20p or 50p coin were arranged so
the distance between one edge and the other, for any line that goes through
the centre, was always the same, irrespective of which part of the flat or
point the line happened to go through and even though the middle of that
line may not always coincide with the centre of the coin.

I think that was so they would be acceptable in slot machines.

Cheers, T i m

On Tue, 26 Jun 2018 17:35:22 +0100, Robin wrote:

On 26/06/2018 16:42, The Natural Philosopher wrote:
On 26/06/18 09:48, Robin wrote:
On 26/06/2018 09:06, The Natural Philosopher wrote:
On 26/06/18 06:31, Richard wrote:

20P and 50P coins have a constant diameter despite not being circular.

No, they do not.


They do for the normal meaning of "diameter" (which is not confined
circles, spheres or other n-spheres)


yes it is.


It would be nice if you would just this once back up your claims with
some evidence that you are right and everyone from the OED to the Royal
Mint are wrong.

He can't. He is a left brainer and because *he* thinks he's right, he
is. ;-)

Cheers, T i m

On 26/06/18 09:06, The Natural Philosopher wrote:
On 26/06/18 06:31, Richard wrote:
On 25/06/18 18:02, The Natural Philosopher wrote:
On 24/06/18 08:03, Richard wrote:
On 23/06/18 17:01, The Natural Philosopher wrote:

No.
Since no wheel is circular using radious as a concept is plain
wrong. At best you can calcualate a '*radius it would be if it were
round*,' from the actual circumference.

The use of radius is completely right.
The circumference doesn't change. The centre of the instantaneous
circle moves closer to the radius.
The tyre is a three dimensional structure and this debate is being
conducted in a two dimensional manner.


I hope no one ebver emp;loys you in an engineering capacity.

I hope so too, as I am not an engineer.


The use of radius is meaningless. The the tyre is not round.

It doesn't have to be. The radius is the distance between the centre
of the object and a point on the perimeter (circumference). In our
case, the point closest to the centre.

No, it is not.

20P and 50P coins have a constant diameter despite not being circular.

No, they do not.



Go and get a technical education

I did, but am always learning.

No, you are not.

I am. Seriously. Today I have learnt that my cat has a deeper
understanding of the constant diameter of 20P and 50P coins than you do.

On Tue, 26 Jun 2018 09:05:15 +0100, The Natural Philosopher
wrote:

snip

My point is that once te tyre is on and deforming, that relationship has
no validity or meaning. I applies to circle only. And the flatter the
tyre is the less circular it is.

YOU and your ilk are claiming that this means that the thing that is
most important is the radius, even though a non circular object has no
constant radius.

What part of the concept of 'an effective radius' can't you get though
your thick left-brained head?

It DOES however have a circumference.

Given that there IS a peripheral distance (because under your rules
there isn't a true circumference either, it not being a circle or
ellipse and all) you *must* also have 'an effective circumference'.
That would be the distance a tyre *actually* travels per revolution.

That doesn't change.

That's the very thing it MUST do for any of the millions of iTPMS to
work!

So, the tread under the load point shrinks reducing the unloaded
(true) circumference to an effective circumference and the real
unloaded radius to an effective radius.

I bet you can understand i or j and how it represents the square root
of a minus number (something that is impossible in straight maths) but
you can't accept how a tyre can change it's effective circumference /
radius when it running at a lower pressure??

Bizarre.

Cheers, T i m

NY wrote
Andy Burns wrote
Chris Bartram wrote

if you have a DSG-equipped VAG car, and it starts refusing to change up
gears

I'm on my second such car, but have not experienced that issue, the
reason for the last one going was that the gearbox was getting "fussy"
...

Do people tend to use DSG-equipped cars in auto or manual mode mainly, I
wonder? I have always found that the big problem with automatics is that
they change down at the wrong time, eg during acceleration, especially
when half-way round a corner or when accelerating out of a roundabout. A
transmission that makes gearchanges more seamless while still allowing the
driver to choose when to change gear (eg during brief gaps in acceleration
when the change is less noticeable) sounds great. I think I'd tend to use
it in automated-manual mode - the best of both worlds - rather than
letting the transmission choose when to change.

Some time I'll have to test drive a VW with DSG and see how easy it is to
drive compared with a) a fully manual gearbox, and b) a
planetary-gear/torque-converter automatic box. At least modern VWs don't
suffer from the problem that (I think) the Mark V Golf TDI had, where the
engine was notoriously easy to stall - rather than being almost
stall-proof, as most diesels are, it seemed to stall even more easily than
a petrol. That Golf is the only car (petrol or diesel) that I have
repeatedly stalled when setting off on a test drive - and the salesman
said I was not alone. It's almost as if the ECU detects that there is
insufficient fuel and therefore insufficient engine torque to be able to
accelerate the car so it deliberately cuts the fuel altogether rather than
letting the engine labour slightly to give the driver chance to increase
the throttle a bit. I imagine that if you drive the car all the time, you
soon get used to it, but for occasional drivers it catches you out.

How easily do people find it is to control the speed accurately at very
slow speed (eg when manoeuvring or when crawling forward in a queue of
traffic).

Do you do that much ? We dont see much of that here, just a bit
of stop start moving while waiting for the lights to change at times.

It may be that I've never developed the muscle memory to be able to
control a car's speed solely on the accelerator, when in a manual car I
tend to control the speed also with the clutch, with a more constant
engine speed.

That certainly explains why you have had to replace clutches a
lot more than I have ever needed to. I have have never had to
ever replace one in will over half a century of driving every day.

For me, the best combination would be a DSG that had a clutch pedal that
was only used for finer control of speed for very slow manoeuvring and
which was not used for gear changes.

IMO it makes more sense for the automatic to be able to do that auto.

With a (conventional) automatic, I'm always scared stiff, especially if
the accelerator pedal/linkage sticks slightly as the car gets older, of
the accelerator pedal moving suddenly and the car surging forwards.

Never had that happen and the obvious way to avoid that is to design the
accelerator so that can never happen. Shouldnt be hard to ensure that.

When I have driven automatics occasionally (eg as hire cars on business
journeys) I've been very aware of this possibility when reversing out of a
parking space and the need to release the accelerator and/or touch the
footbrake the instant that I detect it happening

IMO with an automatic it makes more sense to have one foot on
the brake and one on the accelerator and just brake as required.

- a reflex which I bet elderly drivers who drive into shop fronts haven't
got.

With those the problem appears to just be they press the accelerator instead
of the brake.

It's the only time that I left-foot-brake: as a precaution when inching
forwards/backwards in a car with no manual clutch.

No reason not to do it routinely when parking so you can
always brake when required, even if its some kid running
in front of or behind the car etc.

On Tue, 26 Jun 2018 19:57:42 +1000, "Jeff" wrote:



"Dave Plowman (News)" wrote in message
...
In article ,
Jeff wrote:
No. Once yopu put a non circular tyre on, you vannot talk about radius.

The only distance that matters is the distance between the axle and
the road. That is what determines the rotation rate of the wheel.

Yes, it is better not to call that the radius.

Radius between centre of wheel and point of contact to the road surface.
That is the only relevant part as regards how far the car travels per
rotation of the wheel. Not any theoretical amount.

Yes, but you also have a problem with explaining why it isn't the
circumference of the tyre which doesn’t change much isnt what
determines the rotation rate of the wheel.

Looks like we have a problem explaining it to Turnip so I think he is
just trolling us all now (he asks the question but he neither wants
nor cares for the answer).

Let's agree on some things we can probably all agree and consider to
be facts because of what works ITRW (iTPMS).

1) The unloaded circumference of a car tyre is irrelevant to anything
unless you are just about to take off. ;-)

2) The loaded peripheral length must be different to the unloaded one
and different again under low pressure conditions (for iTPMS to work).

3) The tyre isn't slipping on the rim nor 'skidding' (in the
traditional understanding) on the road whilst in normal use.

4) Steel belted tyres are constructed with the wires set on the
diagonal (as they zig zag across the tread, around the bead and back
again) and form a parallelogram (like a electric train pantograph or
pop rivet gun).

5) One of the FACTS about how a parallelogram works is as it gets
WIDER it becomes SHORTER ... and as it gets longer it gets narrower.

So, as a (car) tyre rotates, it flattens out when it is in contact
with the road and the tyre construction pantographs (because as it
flattens it gets wider) causing the tread to *shrink* longitudinally
(around the periphery) as shown on here ...

http://the-contact-patch.com/book/ro...-contact-patch
Figure 12
Longitudinal compression or bunching of the tread

.... and therefore cause the tyre / wheel to rotate faster than it
would if you compared it with it's unloaded circumference.

So, within practical constraints, from the typical correct running
pressure to something no more than 25% less (to conform with the TPMS
regs), the tyre shortens is peripheral distance (let's call it the
'effective circumference' and of course, an 'effective circumference'
would have an 'effective radius') so that iTPMS can do what they do.

No (in significant terms) scrubbing, no slipping of the tyre on the
rim, no magic, just plain mechanics and physics that even I can fully
understand!

Cheers, T i m

On Wed, 27 Jun 2018 05:38:47 +1000, cantankerous geezer Rot Speed blabbered,
again:

FLUSH the self-opiniated cretin's inevitable senile drivel

--
Sqwertz to Rot Speed:
"This is just a hunch, but I'm betting you're kinda an argumentative
asshole.
MID:

Chris Bartram wrote:
On 26/06/2018 13:43, Andy Burns wrote:
Chris Bartram wrote:

if you have a DSG-equipped VAG car, and it starts refusing to change
up gears

I'm on my second such car, but have not experienced that issue, the
reason for the last one going was that the gearbox was getting "fussy" ...
It *did* make me a bit nervous, but Tim Downie on here somewhere had had
the same. The Leon was approaching 140k when I sold it.


Yep, mIne gave me a fright when it stopped going up through the gears as it
should have. In the end though it wasnt a gearbox problem but a faulty
wheel speed sensor feeding the gearbox erroneous information. Oddly this
didnt show up on the normal computer scans. It was only when it came up as
a brake or ABS problem that the relationship became clear.

Tim

--
Please don't feed the trolls

"Rod Speed" wrote in message
...
How easily do people find it is to control the speed accurately at very
slow speed (eg when manoeuvring or when crawling forward in a queue of
traffic).

Do you do that much ? We dont see much of that here, just a bit
of stop start moving while waiting for the lights to change at times.

Parking (at home and in car parks and on side of road). Moving slowly in
traffic jams (when I can't avoid them).

It may be that I've never developed the muscle memory to be able to
control a car's speed solely on the accelerator, when in a manual car I
tend to control the speed also with the clutch, with a more constant
engine speed.

That certainly explains why you have had to replace clutches a
lot more than I have ever needed to. I have have never had to
ever replace one in will over half a century of driving every day.

What is a good life for a clutch? My earlier cars needed new clutches at
about 70,000 miles. My present car has done 170,000 and is still on its
original clutch - unless the clutch was replaced within the first 18,000 of
its life before I bought the car. The bite point has got gradually higher,
but I can't detect any slippage, even with the handbrake on and trying to
set off in third. I'd say that 170,000 miles is a good life for a clutch.

For me, the best combination would be a DSG that had a clutch pedal that
was only used for finer control of speed for very slow manoeuvring and
which was not used for gear changes.

IMO it makes more sense for the automatic to be able to do that auto.

As long as it is capable of very gradual takeup of power for inching
forwards. I've found with some, you increase the revs, initially nothing
happens and then the clutch kicks in and the car moves faster that you were
expecting so you immediately come off the power (and maybe even brake) to
compensate. On the level the car may creep forward at idling speed with your
foot off the brake, but when going uphill you need a bit of accelerator and
get the sudden kick-in.

With a (conventional) automatic, I'm always scared stiff, especially if
the accelerator pedal/linkage sticks slightly as the car gets older, of
the accelerator pedal moving suddenly and the car surging forwards.

Never had that happen and the obvious way to avoid that is to design the
accelerator so that can never happen. Shouldnt be hard to ensure that.

Yes I wonder why cars still have a Bowden cable to a sensor under the
bonnet, when nowadays the sensor could be right next to the pedal,
eliminating the friction of the Bowden cable.

When I have driven automatics occasionally (eg as hire cars on business
journeys) I've been very aware of this possibility when reversing out of
a parking space and the need to release the accelerator and/or touch the
footbrake the instant that I detect it happening

IMO with an automatic it makes more sense to have one foot on
the brake and one on the accelerator and just brake as required.

- a reflex which I bet elderly drivers who drive into shop fronts haven't
got.

With those the problem appears to just be they press the accelerator
instead of the brake.

It may be a bit of both: maybe (and I'm speculating) they press the
accelerator a bit too hard, panic when the car surges forwards unexpectedly,
and hit the accelerator harder instead of taking their foot off the
accelerator and hitting the brake.


It's the only time that I left-foot-brake: as a precaution when inching
forwards/backwards in a car with no manual clutch.

No reason not to do it routinely when parking so you can
always brake when required, even if its some kid running
in front of or behind the car etc.

I think the normal reason for not using left foot braking, especially if you
are used to driving a manual car and only occasionally drive an automatic,
is that the left leg tends to be used to large movements for operating the
clutch, whereas the right leg is used to finer movements for operating brake
and accelerator. If you brake with your left foot you may subconsciously
press far too hard. Also, it avoids pressing brake and accelerator at the
same time, and stressing the gearbox - for those gearboxes which don't
disengage the drive when the brake pedal is pressed, to avoid this.

In message , T i m
writes
On Tue, 26 Jun 2018 09:05:15 +0100, The Natural Philosopher
wrote:

snip

My point is that once te tyre is on and deforming, that relationship has
no validity or meaning. I applies to circle only. And the flatter the
tyre is the less circular it is.
Snip..

So, the tread under the load point shrinks reducing the unloaded
(true) circumference to an effective circumference and the real
unloaded radius to an effective radius.

This might be the answer:-) The actual circumference varies with
pressure irrespective of the axle road distance.

I bet you can understand i or j and how it represents the square root
of a minus number (something that is impossible in straight maths) but
you can't accept how a tyre can change it's effective circumference /
radius when it running at a lower pressure??

--
Tim Lamb

In article ,
NY wrote:
That certainly explains why you have had to replace clutches a
lot more than I have ever needed to. I have have never had to
ever replace one in will over half a century of driving every day.

What is a good life for a clutch?

Depends on use. Wodney doesn't understand traffic lights so obviously
lives where there is little traffic. So fewer stop starts.

--
*We have enough youth, how about a fountain of Smart?

Dave Plowman London SW
To e-mail, change noise into sound.

On Wed, 27 Jun 2018 10:13:44 +0100, Tim Lamb
wrote:

In message , T i m
writes
On Tue, 26 Jun 2018 09:05:15 +0100, The Natural Philosopher
wrote:

snip

My point is that once te tyre is on and deforming, that relationship has
no validity or meaning. I applies to circle only. And the flatter the
tyre is the less circular it is.
Snip..

So, the tread under the load point shrinks reducing the unloaded
(true) circumference to an effective circumference and the real
unloaded radius to an effective radius.

This might be the answer:-)

Might? ;-)

The actual circumference varies with
pressure irrespective of the axle road distance.

Yes, the pressure affects the peripheral distance (effective
circumference) and that in turn affects the height of the axle over
the road (effective radius). ;-)

Cheers, T i m

NY wrote
Rod Speed wrote

How easily do people find it is to control the speed accurately at very
slow speed (eg when manoeuvring or when crawling forward in a queue of
traffic).

Do you do that much ? We dont see much of that here, just a bit
of stop start moving while waiting for the lights to change at times.

Parking (at home and in car parks and on side of road).

Dont see very slow moving line of cars in either of those situations,
everyone stops while the parking on the side of the road happens
and then moves off when that car has parked. Same with carparks.

Moving slowly in traffic jams (when I can't avoid them).

Dont see much of that either, much more spasmodic.

It may be that I've never developed the muscle memory to be able to
control a car's speed solely on the accelerator, when in a manual car I
tend to control the speed also with the clutch, with a more constant
engine speed.

That certainly explains why you have had to replace clutches a
lot more than I have ever needed to. I have have never had to
ever replace one in will over half a century of driving every day.

What is a good life for a clutch?

I forgot to say that the previous car, the Golf, I used daily for more
than 45 years and only stopped using it when I had stupidly not
bothered to fix the known leaking windscreen and it eventually
rusted the floor and I couldnt be arsed to cut that out and replace it.

My earlier cars needed new clutches at about 70,000 miles.

Like I said, none of mine ever did and they had all done a lot more than
that.

My present car has done 170,000 and is still on its original clutch -
unless the clutch was replaced within the first 18,000 of its life before
I bought the car.

Unlikely.

The bite point has got gradually higher,

Havent seen that either.

but I can't detect any slippage, even with the handbrake on and trying to
set off in third. I'd say that 170,000 miles is a good life for a clutch.

For me, the best combination would be a DSG that had a clutch pedal that
was only used for finer control of speed for very slow manoeuvring and
which was not used for gear changes.

IMO it makes more sense for the automatic to be able to do that auto.

As long as it is capable of very gradual takeup of power for inching
forwards.

Havent seen one that isnt.

I've found with some, you increase the revs, initially nothing happens and
then the clutch kicks in and the car moves faster that you were expecting

Or that either.

so you immediately come off the power (and maybe even brake) to
compensate. On the level the car may creep forward at idling speed with
your foot off the brake, but when going uphill you need a bit of
accelerator and get the sudden kick-in.

Never seen that sudden kick in.

With a (conventional) automatic, I'm always scared stiff, especially if
the accelerator pedal/linkage sticks slightly as the car gets older, of
the accelerator pedal moving suddenly and the car surging forwards.

Never had that happen and the obvious way to avoid that is to design the
accelerator so that can never happen. Shouldnt be hard to ensure that.

Yes I wonder why cars still have a Bowden cable to a sensor under the
bonnet, when nowadays the sensor could be right next to the pedal,
eliminating the friction of the Bowden cable.

Most dont have a bowden cable to the sensor under the bonnet.

When I have driven automatics occasionally (eg as hire cars on business
journeys) I've been very aware of this possibility when reversing out of
a parking space and the need to release the accelerator and/or touch the
footbrake the instant that I detect it happening

IMO with an automatic it makes more sense to have one foot on
the brake and one on the accelerator and just brake as required.

Same with moving forward slowly in a traffic jam too.

- a reflex which I bet elderly drivers who drive into shop fronts
haven't got.

With those the problem appears to just be they press the accelerator
instead of the brake.

It may be a bit of both:

I'm not convinced. The ones that get media coverage are
because someone got injured or the wall got demolished
an in that case it must the wrong pedal was used.

maybe (and I'm speculating) they press the accelerator a bit too hard,
panic when the car surges forwards unexpectedly, and hit the accelerator
harder instead of taking their foot off the accelerator and hitting the
brake.

No evidence that thats what happened.

It's the only time that I left-foot-brake: as a precaution when inching
forwards/backwards in a car with no manual clutch.

No reason not to do it routinely when parking so you can always brake
when required, even if its some kid running in front of or behind the car
etc.

I think the normal reason for not using left foot braking, especially if
you are used to driving a manual car and only occasionally drive an
automatic, is that the left leg tends to be used to large movements for
operating the clutch, whereas the right leg is used to finer movements for
operating brake and accelerator. If you brake with your left foot you may
subconsciously press far too hard.

Yes, I do that a bit now. Didnt used to. I have always had
a manual myself and the work cars were almost always
automatics, and I only do that now, I didnt used to.

Also, it avoids pressing brake and accelerator at the same time, and
stressing the gearbox

Not important enough to matter IMO.

- for those gearboxes which don't disengage the drive when the brake pedal
is pressed, to avoid this.

On Wed, 27 Jun 2018 19:39:54 +1000, cantankerous geezer Rot Speed blabbered,
again:

FLUSH troll ****

--
Richard addressing Rot Speed:
"**** you're thick/pathetic excuse for a troll."
MID:

In article , Andy Burns
writes
bert wrote:

Andy Burns wrote:

I thought you have/had a Disco?
Surprising if such a relatively high centre of mass vehicle didn't
have stability control (or whatever LR call it)

Discos have been around for a long time.

I had a quick search and at least from Disco3 onwards they have a
steering angle sensor, I couldn't see anything either way about earlier
models.
1989 first introduced
From Wiki
Despite such features, the interior's basic structure was the same as
the Range Rover and virtually all the switchgear and instruments came
from other Rover Group cars such as the Maestro and Montego. Similarly,
the Discovery utilised several Range Rover body panels, as well as
headlights from the Freight Rover van and taillights from the Maestro
van. The latter would continue to bear the Austin Rover 'chevron' logo
on their lenses until production of the first generation Discovery ended
in 1998, ten years after Austin Rover ceased to exist.

The designers of the original model had been forced to economise and use
the "parts bin" of the then parent-company, Rover. The 200 series used
the basic body shell structure from the Range Rover, door handles from
the Morris Marina, tail lights from the Austin Maestro van, and interior
switchgear and instrumentation from Rover's surplus parts.

Doesn't sound like they would have anything so sophisticated as a
steering angle sensor.
--
bert

"Rod Speed" wrote in message
...
NY wrote
What is a good life for a clutch?

I forgot to say that the previous car, the Golf, I used daily for more
than 45 years and only stopped using it when I had stupidly not
bothered to fix the known leaking windscreen and it eventually
rusted the floor and I couldnt be arsed to cut that out and replace it.

That is a fantastic life for a car that is used every day. The longest I've
had a car is a little over 10 years from new. Of my past cars (based on DVLA
information) the oldest lasted 18 years until it was last taxed.

My present car has done 170,000 and is still on its original clutch -
unless the clutch was replaced within the first 18,000 of its life before
I bought the car.

Unlikely.

Exactly - I was being facetious.

The bite point has got gradually higher,

Havent seen that either.

That's a standard symptom of clutch wear. To begin with, a self-adjusting
mechanism compensates for greater clutch plate travel as the clutch's
frictional surfaces wear, but eventually the end of that self-adjusting
range is reached and the clutch pedal has to be raised higher off the floor
before the bite point is reached. I suppose in theory a garage could make a
manual adjustment to the cable (or fluid mechanism) so the bite point is
reached with the pedal closer to the floor, where it is easier to control
without lifting your heel off the floor.

Yes I wonder why cars still have a Bowden cable to a sensor under the
bonnet, when nowadays the sensor could be right next to the pedal,
eliminating the friction of the Bowden cable.

Most dont have a bowden cable to the sensor under the bonnet.

Ah. I remember my first two fuel-injected cars in the 1990s had a big rotary
variable resistor under the bonnet, roughly where a carburettor used to be,
operated by a Bowden cable. I've just checked my present car and I can't see
any sign of something like that so they've stopped doing it that way now.

With those the problem appears to just be they press the accelerator
instead of the brake.

It may be a bit of both:

I'm not convinced. The ones that get media coverage are
because someone got injured or the wall got demolished
an in that case it must the wrong pedal was used.

maybe (and I'm speculating) they press the accelerator a bit too hard,
panic when the car surges forwards unexpectedly, and hit the accelerator
harder instead of taking their foot off the accelerator and hitting the
brake.

No evidence that thats what happened.

If you get to hear a driver's account of what happened, it's usually along
the lines of "the car suddenly surged forward - I don't know how it
happened" which could be either excessive pressure on the accelerator or
pressing the accelerator instead of the brake. It's difficult to tell from
the small amount of information you usually hear about the cause.

On Wed, 27 Jun 2018 10:13:44 +0100, Tim Lamb
wrote:

In message , T i m
writes
On Tue, 26 Jun 2018 09:05:15 +0100, The Natural Philosopher
wrote:

snip

My point is that once te tyre is on and deforming, that relationship has
no validity or meaning. I applies to circle only. And the flatter the
tyre is the less circular it is.
Snip..

So, the tread under the load point shrinks reducing the unloaded
(true) circumference to an effective circumference and the real
unloaded radius to an effective radius.

This might be the answer:-) The actual circumference varies with
pressure irrespective of the axle road distance.

sabino56's post helps clarify some of the misconceptions occuring in
this thread:

https://www.hotrodders.com/forum/how...er-101007.html

and in brief:

1) the diameter does change with load/pressure/speed

2) the effective radius does change with load/pressure/speed

The effective radius has more affect on gearing than on diameter.



--
AnthonyL

On 26/06/2018 14:24, Andy Burns wrote:
Dave Plowman wrote:

Andy Burns wrote:

the gearbox was getting "fussy"

Did wonder what the expected life of these boxes is compared to a
conventional auto.

My first one was 'chauffeur smooth' for a year, then as good as a decent
driver with a manual for 3-4 years, very enjoyable.

Then, on cold mornings, it sometimes gave a bit of a thump in your back
the first time it came to a halt as it was changing down into 1st, as
though it wasn't sure of the bite point, I had it recalibrated at next
service it was better for 6 months then started doing the same again, it
then occasionally put the gearbox into "limp mode" for few seconds after
long journeys on hot days, only ever a warning, not an error.Â* Main
dealer option at that point was a "DSG rebuild kit", not cheap, and not
much guarantee.

OBD cable showed it was occasionally unhappy with pressures and
temperatures of hydraulic clutch valves, so it got chopped in, maybe
I'll resist using the launch control on this one :-)


I never had the nerve to use luanch control, and the Leon got to 140K
with no significant problems with the box itself. It would cometimes
lurch a little into 2nd when very hot (as Dave experienced with PDK
they're very keen to get out of 1st), but my current one shows no such
problems, being very smooth all the time. I did run the basic settings
on the Leon (I have VCDS) a few times, and it would make a *little*
difference for a while. Not serious enough to worry about, and no fault
codes.

The briskoda forums had someone with nearly 600K kilometres on a DSG
Octavia. Certainly, all the earlyntales of them failing at 60k seem
unfounded.

Was on a London single decker bus the other day that appeared to have an
SMG type auto, and that crunched when changing up into what I think was
third gear. Like you get with worn synchromesh.

I thought they were pre-selector boxes?

Not now. I think there's some DCTs, but lots of fairly conventional
autoboxes.

On 26/06/2018 22:32, Tim+ wrote:
Chris Bartram wrote:
On 26/06/2018 13:43, Andy Burns wrote:
Chris Bartram wrote:

if you have a DSG-equipped VAG car, and it starts refusing to change
up gears

I'm on my second such car, but have not experienced that issue, the
reason for the last one going was that the gearbox was getting "fussy" ...
It *did* make me a bit nervous, but Tim Downie on here somewhere had had
the same. The Leon was approaching 140k when I sold it.


Yep, mIne gave me a fright when it stopped going up through the gears as it
should have. In the end though it wasnt a gearbox problem but a faulty
wheel speed sensor feeding the gearbox erroneous information. Oddly this
didnt show up on the normal computer scans. It was only when it came up as
a brake or ABS problem that the relationship became clear.

Tim

Yes, ISTR I dropped you an email and you pointed me in the right
direction, and then a few days later my car did exactly the same as your
Touran, lighting up the ESP and ABS.

On 27/06/2018 09:18, NY wrote:


What is a good life for a clutch? My earlier cars needed new clutches at
about 70,000 miles. My present car has done 170,000 and is still on its
original clutch - unless the clutch was replaced within the first 18,000
of its life before I bought the car. The bite point has got gradually
higher, but I can't detect any slippage, even with the handbrake on and
trying to set off in third. I'd say that 170,000 miles is a good life
for a clutch.


Very dependent on use (and abuse).

For me, the best combination would be a DSG that had a clutch pedal
that was only used for finer control of speed for very slow
manoeuvring and which was not used for gear changes.

IMO it makes more sense for the automatic to be able to do that auto.

As long as it is capable of very gradual takeup of power for inching
forwards. I've found with some, you increase the revs, initially nothing
happens and then the clutch kicks in and the car moves faster that you
were expecting so you immediately come off the power (and maybe even
brake) to compensate. On the level the car may creep forward at idling
speed with your foot off the brake, but when going uphill you need a bit
of accelerator and get the sudden kick-in.


I drove a Toyota MMT like that. Vile. DSG (and the Ford equivalent)
generally does OK.



Yes I wonder why cars still have a Bowden cable to a sensor under the
bonnet, when nowadays the sensor could be right next to the pedal,
eliminating the friction of the Bowden cable.

A lot do exactly that now.

In article ,
NY wrote:
Ah. I remember my first two fuel-injected cars in the 1990s had a big
rotary variable resistor under the bonnet, roughly where a carburettor
used to be, operated by a Bowden cable. I've just checked my present
car and I can't see any sign of something like that so they've stopped
doing it that way now.

Called a throttle position sensor (TPS). But it was the throttle butterfly
which was operated by the bowden cable - same as that on a carb. The pot
merely sending a signal to the ECU to give the butterfly position.

Most modern cars are 'drive by wire' with no throttle cable. So the ECU
knows what the throttle is doing without that pot.

--
*If one synchronized swimmer drowns, do the rest have to drown too?

Dave Plowman London SW
To e-mail, change noise into sound.

One thing I have noticed with the PDK is creeping along in a traffic jam -
ie continual start stop - isn't quite as easy as with a conventional auto
with torque convertor. Although they have built in 'creep' to try and
emulate this.

--
*Why is the word abbreviation so long? *

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ,
NY wrote:
Ah. I remember my first two fuel-injected cars in the 1990s had a big
rotary variable resistor under the bonnet, roughly where a carburettor
used to be, operated by a Bowden cable. I've just checked my present
car and I can't see any sign of something like that so they've stopped
doing it that way now.

Called a throttle position sensor (TPS). But it was the throttle butterfly
which was operated by the bowden cable - same as that on a carb. The pot
merely sending a signal to the ECU to give the butterfly position.

One car was a petrol and the other was a diesel, so only the petrol would
have had a throttle butterfly. I'd assumed that *all* fuel-injected cars had
an electrically-operated butterfly, with the ECU generating a control signal
that was partly determined by accelerator position sensor but partly
influenced by other considerations so as to avoid over-fuelling the
cylinders if there was any unburnt fuel coming out of the exhaust. Maybe not
at one time.

The diesel is more peculiar, because presumably there is nothing mechanical
that the pedal could control - just a fuel dose whose timing and amount will
be dependent on ECU. Or maybe on that car (Pug 306) the pedal controlled the
amount mechanically and the ECU only controlled the timing.

I'm not sure how fuel injection works. Obviously you can vary the amount of
fuel admitted by varying the length of time that an injector valve is open,
but is any attempt made to vary the pressure and therefore the fuel flow
rate, to avoid having to inject for longer to get more fuel in, as opposed
to keeping a more constant injection period but varying the flow rate?

I had endless problems with the petrol car (a Golf): the engine would very
occasionally die without any warning, just as I'd set off to pull out of a
junction - which was bloody scary to have a car or bus bearing down on you
as you were blocking both sides of the road when turning right and the
engine has lost all power and doesn't want to restart :-( After extensive
(and expensive) investigations by the garage on several occasions, they
traced it to a worn track on the throttle potentiometer. Fortunately I could
produce a garage receipt which showed that the car had been about a hundred
miles below the expiry mileage for the manufacturer's warranty when I first
reported the fault, even though the car was several thousand miles over by
the time they identified and fixed it. I left it for the garage and VAG head
office to decide who would pay. From the sarky comments when I collected the
car and the vibes of "we don't want your business any more", I got the
impression that head office had said the garage itself had to pay the bill
;-)

In article ,
NY wrote:
One car was a petrol and the other was a diesel, so only the petrol
would have had a throttle butterfly. I'd assumed that *all*
fuel-injected cars had an electrically-operated butterfly, with the ECU
generating a control signal that was partly determined by accelerator
position sensor but partly influenced by other considerations so as to
avoid over-fuelling the cylinders if there was any unburnt fuel coming
out of the exhaust. Maybe not at one time.

My early BMW E39 - 1997 - had a cable throttle. Later on in that model run
- about 2000 - it changed to drive by wire.

--
*How do you tell when you run out of invisible ink? *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
NY wrote:
I'm not sure how fuel injection works. Obviously you can vary the amount
of fuel admitted by varying the length of time that an injector valve
is open, but is any attempt made to vary the pressure and therefore the
fuel flow rate, to avoid having to inject for longer to get more fuel
in, as opposed to keeping a more constant injection period but varying
the flow rate?

Not absolutely certain of all the latest techniques, but at one time fuel
pressure to the injectors was compensated for against 'suck' with high
cylinder vacuum by having the pressure regulator referenced to vacuum. So
it dropped the pressure under high vacuum conditions.

In other words the amount of fuel injected was basically controlled by the
length of time the injector was open. This being the common way with port
injection petrol engines.

--
*Speak softly and carry a cellular phone *

Dave Plowman London SW
To e-mail, change noise into sound.

NY wrote
Rod Speed wrote
NY wrote
What is a good life for a clutch?

I forgot to say that the previous car, the Golf, I used daily for more
than 45 years and only stopped using it when I had stupidly not
bothered to fix the known leaking windscreen and it eventually
rusted the floor and I couldnt be arsed to cut that out and replace it.

That is a fantastic life for a car that is used every day.

And it required very little in the way of repairs in that time, just
an alternator regulator, distributor thing and an indicator relay.

The distributor arm was almost certainly due to me choosing to
remove it to prevent theft of the car when I was away from home
without taking the car. And the car never spent any time in the
garage or carport either, because I never got around to building one.

The longest I've had a car is a little over 10 years from new.

My current Hyundai Getz is older than that but doesnt
get daily use now I have retired and I got it after I retired.

Both bought new.

Of my past cars (based on DVLA information) the oldest lasted 18 years
until it was last taxed.

The bite point has got gradually higher,

Havent seen that either.

That's a standard symptom of clutch wear.

Sure, I meant I havent seen that level of wear in any car of mine.

To begin with, a self-adjusting mechanism compensates for greater clutch
plate travel as the clutch's frictional surfaces wear, but eventually the
end of that self-adjusting range is reached and the clutch pedal has o be
raised higher off the floor before the bite point is reached. I suppose in
theory a garage could make a manual adjustment to the cable (or fluid
mechanism) so the bite point is reached with the pedal closer to the
floor, where it is easier to control without lifting your heel off the
floor.

Yes I wonder why cars still have a Bowden cable to a sensor
under the bonnet, when nowadays the sensor could be right next to the
pedal, eliminating the friction of the Bowden cable.

Most dont have a bowden cable to the sensor under the bonnet.

Ah. I remember my first two fuel-injected cars in the 1990s had a big
rotary variable resistor under the bonnet, roughly where a carburettor
used to be, operated by a Bowden cable. I've just checked my present car
and I can't see any sign of something like that so they've stopped doing
it that way now.

Yeah, very crude approach to morphing the design IMO. What brands ?

With those the problem appears to just be they press the accelerator
instead of the brake.

It may be a bit of both:

I'm not convinced. The ones that get media coverage are
because someone got injured or the wall got demolished
an in that case it must the wrong pedal was used.

maybe (and I'm speculating) they press the accelerator a bit too hard,
panic when the car surges forwards unexpectedly, and hit the accelerator
harder instead of taking their foot off the accelerator and hitting the
brake.

No evidence that thats what happened.

If you get to hear a driver's account of what happened, it's usually along
the lines of "the car suddenly surged forward - I don't know how it
happened" which could be either excessive pressure on the accelerator or
pressing the accelerator instead of the brake. It's difficult to tell from
the small amount of information you usually hear about the cause.

I've never seen a car surge forward that dramatically except
when the accelerator is used instead of the brake accidentally.

I forgot to say that the previous car, the Golf, I used daily for more
than 45 years and only stopped using it when I had stupidly not
bothered to fix the known leaking windscreen and it eventually
rusted the floor and I couldnt be arsed to cut that out and replace it.

That is a fantastic life for a car that is used every day.

And it required very little in the way of repairs in that time, just
an alternator regulator, distributor thing and an indicator relay.

The distributor arm was almost certainly due to me choosing to
remove it to prevent theft of the car when I was away from home
without taking the car. And the car never spent any time in the
garage or carport either, because I never got around to building one.

My cars have generally had the normal wear and tyre things (brake
pads/discs, tyres, cambelt (and water pump*) at recommended mileage) that
you would expect. My previous Peugeot had to have a new "fanbelt" and that
replacement one lasted only a few thousand miles before it failed. On closer
inspection, it was found that one of the pulleys had warped, *causing* the
second (and probably the first) belt to fail. Sadly garage (the local one in
my village) denied liablility, so I had to pay for both belts and (more
importantly) the labour to fit them.

My present Pug had a failed clutch actuator mechanism (**) - failed in-gear
as I was setting off at the head of a queue of traffic at lights, so without
the ability to disengage the clutch, the car was stuck in gear and I was
stuck blocking the junction. Embarrassing. And this car has had various
problems with its anti-pollution system - extra complexity leads to extra
failure points. A new diesel particulate filter and a new cat (at the same
time) are not nice bills to have to pay for :-(

Still, it's going strong now and is worth a lot more to me as a car than its
resale value.

That's a standard symptom of clutch wear.

Sure, I meant I havent seen that level of wear in any car of mine.

I suppose it you don't do much stop-start driving or having to hill-start on
steep hills, the clutch wear will be less than mine. There is a notorious
1:3 hill near where I used to live and twice I've had to stop and restart
when the car in front of me has got into difficulties. Setting off is
"interesting" on a 1:3 hill: you need good handbrake/clutch/accelerator
coordination. I tried not to think about the wear that it would be putting
on the clutch.

Ah. I remember my first two fuel-injected cars in the 1990s had a big
rotary variable resistor under the bonnet, roughly where a carburettor
used to be, operated by a Bowden cable. I've just checked my present car
and I can't see any sign of something like that so they've stopped doing
it that way now.

Yeah, very crude approach to morphing the design IMO. What brands ?

VW Gold Mark III (1992), Peugeot 306 with the non-HDi engine (1995).


(*) Since the water pump is driven from the cambelt, the garage advises that
while they have dismantled everything to replace the cambelt, they should
replace the water pump even if it seems to be OK, since the cost of the pump
is much less than the labour to replace it later on - kill two birds with
one stone.

(**) Functionally equivalent to the clutch cable snapping. I think the pedal
connects by cable to an intermediate hydraulic actuator which in turn moves
the clutch plate, rather than the cable being directly connected.

On 27/06/18 12:14, AnthonyL wrote:
On Wed, 27 Jun 2018 10:13:44 +0100, Tim Lamb
wrote:

In message , T i m
writes
On Tue, 26 Jun 2018 09:05:15 +0100, The Natural Philosopher
wrote:

snip

My point is that once te tyre is on and deforming, that relationship has
no validity or meaning. I applies to circle only. And the flatter the
tyre is the less circular it is.
Snip..

So, the tread under the load point shrinks reducing the unloaded
(true) circumference to an effective circumference and the real
unloaded radius to an effective radius.

This might be the answer:-) The actual circumference varies with
pressure irrespective of the axle road distance.

sabino56's post helps clarify some of the misconceptions occuring in
this thread:

https://www.hotrodders.com/forum/how...er-101007.html


More idiots who cant do mecahniacval engineering

and in brief:

1) the diameter does change with load/pressure/speed

Ther is no such thiung as diameter

2) the effective radius does change with load/pressure/speed

No, only with pressure and then only a little

The effective radius has more affect on gearing than on diameter.

Its all crap.





--
"I guess a rattlesnake ain't risponsible fer bein' a rattlesnake, but ah
puts mah heel on um jess the same if'n I catches him around mah chillun".