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scott wrote:
>
> Well of course if you are deliberately aiming for such things, I can
> never resist blipping the accelerator on an empty snowy corner to get a
> bit of sideways action :-D
Doesn't help me, while I'm driving FWD as daily ride.
> If only I had the skill to do this with my car without crashing! (but
> not the stupidity to do it while there's other traffic arround).
>
> http://www.youtube.com/watch?v=buZ5407L718
Nnnnnice, proper 4WD sliding is always fun to watch, but as you say, it
doesn't belong there where this was shooted.
> Hehe I love mine, but first I always have to hold down some button for 5
> seconds to really turn off all the driving aids (just pressing it only
> turns them half off). Actually 99% of the time I have all the driving
> aids turned on (that's the default), they really are quite impressive at
> keeping the car going the direction you are pointing.
Same for me with ESP, even though most slides (practically all I've
faced) would piece of cake to take control or even get back controlled
by the natural movement of the car - Audi B8 is actually pretty easy and
nice to handle in such manners.
-Aero
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Jim Henderson wrote:
>
> Well, I've only got something like 20 years of experience driving during
> winters in Minnesota and Utah to call on.
I only have 10 in Finland :-). Honestly, I have no idea what kind of
winters there is at Utah or Minnesota, but I assume that means there's
snow and ice available enough.
> It's been my experience that
> it is generally more effective to downshift and let the engine do the
> work.
How could it be? In both styles the negative acceleration is applied to
the ground via tires and tire/ground -layer being the weakest part -
with downshifting most cars do it practically via 1 wheel, almost no car
makes it via 4 wheel (which would mean 4WD with completely locked
differentials), while brakes are applied via all 4 wheels. Breaking with
the engine is of course more economical
> Unless you know with relative precision how slippery it is,
> tapping the breaks can be a bad prospect.
There might be a language wall here - I'd consider tapping as a slight
touch and hitting the brakes as a 'do-not-do' -movement on ice.
> I've managed to put two cars in the ditch in 20 years. One from
> overcorrecting a spin, and one for not slowing down enough because some
> jackass was tailgating me. I've never managed to put my car in the ditch
> by stepping on the brakes, because I was taught not to do that and I
> don't. <shrug> I can't argue with what works for me.
We have the same ratio, I've put one in 10 years :). That was due to
lifting the gas pedal while coming back to my lane after overtaking
another car. And well, that was actually no ditch AFAIK, while the same
car is still mine and registered (just now out of the traffic, though -
it's my summer toy).
And I'm not saying that braking with the engine doesn't work - I'm
saying that braking with the brakes works too, it just needs to be done
carefully.
> Yes, that will also work, but yes, it is dependent on knowing the
> condition of your tires. I think we both can agree that there is a high
> degree of situational awareness called for.
*Everything* while driving on ice is dependent on knowing the condition
of tires, more or less. As pointed out, RWD can give you a spin (or try
it) with downshifting, if the road is too slippery. It's always
necessary to know what kind of tires you're driving on and what's their
condition. What I ment is that to test the possibilities to brake with
accelerating you'll need to know the ratio of acceleration traction and
braking traction of your tires. Eg. I once had tires (Kleber Kapnor 4
185/65/15) which were catastrophic when accelerating, but pretty good
when turning and braking.
> Yes, agreed - the more you can practice in a safe environment, the better
> prepared you'll be. :-)
And the more fun you'll have (while practicing, of course), so it's a
win-win situation :-).
> Jim
-Aero
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scott wrote:
> If only I had the skill to do this with my car without crashing!
I'm not sure it's his car. He has a price written on the window. :-)
I suspect he may be taking a used car for a test drive. ;-)
--
Darren New, San Diego CA, USA (PST)
"Ouch ouch ouch!"
"What's wrong? Noodles too hot?"
"No, I have Chopstick Tunnel Syndrome."
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On Tue, 10 Feb 2009 17:57:00 +0200, Eero Ahonen wrote:
> Jim Henderson wrote:
>>
>> Well, I've only got something like 20 years of experience driving
>> during winters in Minnesota and Utah to call on.
>
> I only have 10 in Finland :-). Honestly, I have no idea what kind of
> winters there is at Utah or Minnesota, but I assume that means there's
> snow and ice available enough.
Yes, and plenty of it in both places. Drove into work on ice and snow
today, in fact - and slid turning into the parking lot at work. :-)
>> It's been my experience that
>> it is generally more effective to downshift and let the engine do the
>> work.
>
> How could it be? In both styles the negative acceleration is applied to
> the ground via tires and tire/ground -layer being the weakest part -
> with downshifting most cars do it practically via 1 wheel, almost no car
> makes it via 4 wheel (which would mean 4WD with completely locked
> differentials), while brakes are applied via all 4 wheels. Breaking with
> the engine is of course more economical
By downshifting, what happens is the wheels aren't stopped, but the
torque applied through the drivetrain slows them down as the engine revs
come down. This has been my experience in 4 cars, including the first
car I drove (a manual) - but of course you have to be more careful in a
manual when downshifting - usually I'd start by just putting the clutch
in and letting the car coast. I did actually get to the point with that
car, though, that I could shift if I needed to without using the clutch,
just listen to the engine and when it got to the right speed, shifting
without the clutch wasn't a problem. I don't know if it's that easy to
do in newer manual transmission cars, though - that old car was a '74
Duster, manual *everything*, power *nothing*. ;-)
>> Unless you know with relative precision how slippery it is, tapping the
>> breaks can be a bad prospect.
>
> There might be a language wall here - I'd consider tapping as a slight
> touch and hitting the brakes as a 'do-not-do' -movement on ice.
It depends on the road conditions. For example, this morning as I turned
left into the parking lot at the office, the car's momentum overcame the
friction of the tires on the ice, and I ended up not turning as per usual
but sliding instead. In that case, pumping the breaks was an effective
way to slow the car down. Similar effect to a car with ABS (which I
really miss in my current car, my last one had ABS but the new one
doesn't), but the pulsing isn't rapid.
If a car has ABS, you can get away with hitting the breaks, because the
ABS system will prevent the wheels from locking up.
>> I've managed to put two cars in the ditch in 20 years. One from
>> overcorrecting a spin, and one for not slowing down enough because some
>> jackass was tailgating me. I've never managed to put my car in the
>> ditch by stepping on the brakes, because I was taught not to do that
>> and I don't. <shrug> I can't argue with what works for me.
>
> We have the same ratio, I've put one in 10 years :). That was due to
> lifting the gas pedal while coming back to my lane after overtaking
> another car. And well, that was actually no ditch AFAIK, while the same
> car is still mine and registered (just now out of the traffic, though -
> it's my summer toy).
:-)
> And I'm not saying that braking with the engine doesn't work - I'm
> saying that braking with the brakes works too, it just needs to be done
> carefully.
Yes, and I can agree with that. The problem is that most people don't do
it carefully enough, and end up like the SUV I saw on the way into work
today - wrecked.
>> Yes, that will also work, but yes, it is dependent on knowing the
>> condition of your tires. I think we both can agree that there is a
>> high degree of situational awareness called for.
>
> *Everything* while driving on ice is dependent on knowing the condition
> of tires, more or less. As pointed out, RWD can give you a spin (or try
> it) with downshifting, if the road is too slippery. It's always
> necessary to know what kind of tires you're driving on and what's their
> condition. What I ment is that to test the possibilities to brake with
> accelerating you'll need to know the ratio of acceleration traction and
> braking traction of your tires. Eg. I once had tires (Kleber Kapnor 4
> 185/65/15) which were catastrophic when accelerating, but pretty good
> when turning and braking.
We are in violent agreement. ;-)
>> Yes, agreed - the more you can practice in a safe environment, the
>> better prepared you'll be. :-)
>
> And the more fun you'll have (while practicing, of course), so it's a
> win-win situation :-).
:-)
Jim
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>> It's been my experience that
>> it is generally more effective to downshift and let the engine do the
>> work.
>
> How could it be? In both styles the negative acceleration is applied to
> the ground via tires and tire/ground -layer being the weakest part -
> with downshifting most cars do it practically via 1 wheel, almost no car
> makes it via 4 wheel (which would mean 4WD with completely locked
> differentials), while brakes are applied via all 4 wheels.
Maybe in some cars with sensitive brake pedals it's easier to control the
small amount of negative acceleration through the clutch/gears/accelerator
than through the brake pedal?
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> By downshifting, what happens is the wheels aren't stopped, but the
> torque applied through the drivetrain slows them down as the engine revs
> come down.
The brakes do the same. And in both cases, as soon as the negative torque
(either from engine or brakes) is higher than the friction between the tyre
and road, the wheels lock. As I said in my other post, maybe it's easier to
control small amounts of negative torque with the gears, but still you're
only applying it to 1 or 2 wheels, not 4, so you're never going to be able
to slow down as quickly.
> In that case, pumping the breaks was an effective
> way to slow the car down. Similar effect to a car with ABS (which I
> really miss in my current car, my last one had ABS but the new one
> doesn't), but the pulsing isn't rapid.
They make cars without ABS?
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On Wed, 11 Feb 2009 09:14:57 +0100, scott wrote:
>> By downshifting, what happens is the wheels aren't stopped, but the
>> torque applied through the drivetrain slows them down as the engine
>> revs come down.
>
> The brakes do the same. And in both cases, as soon as the negative
> torque (either from engine or brakes) is higher than the friction
> between the tyre and road, the wheels lock. As I said in my other post,
> maybe it's easier to control small amounts of negative torque with the
> gears, but still you're only applying it to 1 or 2 wheels, not 4, so
> you're never going to be able to slow down as quickly.
Um, no, the brakes don't do the same - if you have disc brakes, the
brakes stop the wheels when fully engaged (I don't have drum brakes so I
can't comment on those). Conversely, by downshifting, you increase the
engine revs and the wheels are not locked - they still turn.
Now, when you're on dry pavement, the wheels normally don't lock because
the car's momentum overcomes the friction on the brakes, bringing you to
a gentle (or sometimes less-than-gentle) stop. On ice, though, it takes
less friction of the brake pads against the wheel to stop the wheels
because it takes less to overcome the friction of the wheel against the
ground.
So it's easier to lock the wheels up and skid.
However, you're right that you won't slow down as quickly by using the
engine to slow the vehicle down. The point isn't to slow down quickly,
it's to slow down safely.
You have to combine this with driving more defensively as well - not
following the car ahead of you too closely, for example. If you don't
give yourself more space to stop, you'll run into someone else.
But that gets into another whole area of "stupid driver tricks".
>> In that case, pumping the breaks was an effective way to slow the car
>> down. Similar effect to a car with ABS (which I really miss in my
>> current car, my last one had ABS but the new one doesn't), but the
>> pulsing isn't rapid.
>
> They make cars without ABS?
Yes. My 1999 Saturn SC1 has no ABS. :-)
Jim
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Jim Henderson wrote:
> a gentle (or sometimes less-than-gentle) stop.
I once gave myself a nosebleed by borrowing my mother's car. I was used to
driving a dinky manual without power breaks. I borrowed the behemoth car my
parents drove, and as I coasted up to the stop sign, I stomped the clutch
all the way to the floor, of course. Except their car had very strong power
breaks and was an automatic with no clutch pedal. Ouch.
--
Darren New, San Diego CA, USA (PST)
"Ouch ouch ouch!"
"What's wrong? Noodles too hot?"
"No, I have Chopstick Tunnel Syndrome."
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On Wed, 11 Feb 2009 10:42:40 -0800, Darren New wrote:
> Jim Henderson wrote:
>> a gentle (or sometimes less-than-gentle) stop.
>
> I once gave myself a nosebleed by borrowing my mother's car. I was used
> to driving a dinky manual without power breaks. I borrowed the behemoth
> car my parents drove, and as I coasted up to the stop sign, I stomped
> the clutch all the way to the floor, of course. Except their car had
> very strong power breaks and was an automatic with no clutch pedal.
> Ouch.
Ouch indeed. Kinda the reverse of what nearly everyone I know who
learned to drive a stick went through when not timing the clutch properly
when shifting. Of course, you lurch forward (usually) rather than
backwards, so a nosebleed isn't so much of a problem as whiplash. ;-)
Jim
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Jim Henderson wrote:
> Ouch indeed. Kinda the reverse of what nearly everyone I know who
> learned to drive a stick went through when not timing the clutch properly
> when shifting.
Oh, I did that too. This was years after I learned to drive a stick. I just
wasn't really paying attention to the controls as such. Just, you know, drivin'.
--
Darren New, San Diego CA, USA (PST)
"Ouch ouch ouch!"
"What's wrong? Noodles too hot?"
"No, I have Chopstick Tunnel Syndrome."
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