> > We professional driving instructors teach "block changing" as it is called,
> > as standard practice for all road drivers when changing down.
> Are you a racing instructor ?
Race Communications Association
http://www.racesimcentral.net/
Holodyne Engineering
Mystic Music
(have Your !!Name/Address!! placed here)
Well, lets see. Read on..
Quotes? I was -quoting- the original poster. That part, of course
was snipped by the person I replied to, and apparently not seen
by you.
Great. Of course that wasn't what the original poster said. Also,
he recommended 5th to 2nd as a normal driving style, and he didn't
qualify his post by letting us in on the speed he was traveling.
Well, IMO, that depends on how fast you're going. Do you Brits
ever drive above 60MPH? In the U.S. we do it all the time, and we
mostly avoid shifting down from 5th to 2nd at those speeds.
How fast do you drive? Do you shift from 5th to 2nd at 65MPH on
one of those famous slippery roads in the U.K.? LOL!
I believe in letting someone scare themself as much as they want to.
I just don't believe that the original poster who claims to be a
"professional driving instructor" should teach methods to -cause- fear
as a normal part of driving school.
>>On 23 Aug 1999 11:33:48 GMT,
>>>>Try 4th -> 3rd at 65 mph and see if you get any braking, even if you
>have
>>>>a 50hp engine, such as a VW, etc..
>>>>Clue... you WILL get lots of braking.
>>>VERY little compared to the effect from hitting the brakes.
>>Well I know that.. LOL!!!...
>>The original 'professional' instructor claimed there would be little to
>>no effect from shifting down, unless you had over 300hp, but you
>>snipped that. He claimed that it is a good idea to shift down from
>>5th-2nd, since the effect would be negligible. I pointed out that
>>his recommendation would not be a good idea on slick surfaces, at
>>highway speeds.
>>Do you agree with him?
>>>>FWIW, engine braking has -nothing- to do with HP. It has to do with
>>>>gear ratios, compression ratios, general engine friction and flywheel
>>>>weight for the most part.
>>>>Mark, you, as a 'professional' driving instructor are not -really-
>teaching
>>>>people this stuff are you? I hope not, because you could get them killed.
>>>FWIW, engine braking IS measured in horsepower, just look at the specs for
>any
>>>commercial truck engine.
>>So you believe, as the original poster (which you totally snipped) that
>>unless you have over 300hp the braking from shifting down will be
>>negligible?
>>Tell us, and please don't continue to snip the context from the thread.
>>Thanks.
>>>Getting a truck stopped is much harder than getting a
>>>car stopped because of the weight involved. (guess that's obvious, duh)
>>Trucks? Yawn..
>>>Truck
>>>engine manufacturers scream about this measurement almost as loudly as
>they do
>>>for torque and horsepower.
>>[shrug]
>>>A truck engine optimized for braking will have
>>>about 2/3 the braking power as acceleration power. A car engine is
>probably
>>>about 1/3.
>>Kewl.
>>>Compare these numbers to the easy 1000 horsepower the average road
>>>car brakes can produce and you'll see why the effect is minor on overall
>>>braking.
>>Hey Don, what happens when you slam the shifter from 5th to
>>2nd, at 65mph, on a wet highway, in a 50hp Volkswagen?
>>>Don McCorkle
>>>Libertarian Motorsports
>>Now Don, please attempt to answer the questions I have asked and
>>try to avoid snipping the context from the thread. Thanks again.
>>BTW, I don't know about (or care about) trucks, but I do know a
>>little about cars.
>>>Try 4th -> 3rd at 65 mph and see if you get any braking, even if you have
>>>a 50hp engine, such as a VW, etc..
>>>Clue... you WILL get lots of braking.
>>VERY little compared to the effect from hitting the brakes.
>Well I know that.. LOL!!!...
>The original 'professional' instructor claimed there would be little to
>no effect from shifting down, unless you had over 300hp, but you
>snipped that. He claimed that it is a good idea to shift down from
>5th-2nd, since the effect would be negligible. I pointed out that
>his recommendation would not be a good idea on slick surfaces, at
>highway speeds.
>Do you agree with him?
I don't care what horsepower you have, the brakes are capable of exceeding the
tires' coefficient of friction on any car ever made. Engine braking can be
usefull to change the front to rear bias, but will do nothing to increase the
available braking.
I have snipped nothing, and resent that you are trying to make it look as if
I'm hiding something. Perhaps I quoted from a post someone else had snipped,
but trust me here, I SNIPPED NOTHING.
Again, I have not snipped anything.
Don McCorkle
Libertarian Motorsports
PS: If this discussion is going to continue, please snip it a bit. It's going
to be real ponderous to read, but I'm afraid to now. :-)
It won't continue because you don't grasp anything that
was originally said by the profesional.
I quit.
--
* rrevved at mindspring dot com
* http://www.cabal.net
* http://www.sputum.com
No you won't because most of the braking is done BEFORE you change to the
lower gear. It is for exactly these sort of conditions that this technique
is used to keep ON the road. Of course, if you know better than 30,000 odd
instructors and disagree with "Roadcraft", The police driving
manual...............!!!
And you about know the increased odds of locking up wheels in the wet under
braking, when the transmission is being repeatedly disengaged and engaged,
introducing all manner of other forces to the rear wheels right?
Don't insult my intelligence please. Of course engine braking force will
increase with speed. Why not try doing it at 100mph and watch your valves
come up to introduce themselves through the bonnet! Let's try another
experiment. Let's get into our cars and drive towards a wall, side by side
at 60 mph. You use your gears to slow up and I'll use my brakes. Let's see
who ends up in hospital. The whole point is that brakes on road cars are
powerful enough to exceed the performance of any road tyre. Why the hell do
you think all class 1 police pursuit drivers use this method
I think that woodie has posted a good answer to this already Ed :-)
I have 3248 test passes to date. How many do you have ;-)
No offence mate but leave it to the pros eh
Mark
Err - I do
But I want to!
Hehe - I remember a similar debate when a police driving instructor came to
give a talk to all the budding rally/race drivers (including me) at our
local motor club. He explained how the police are (were?) trained to double
declutch & never to perform more actions than necessary at one time. Hence
braking & double de-clutching was a no-no! Therefore they would NOT change
down and brake at the same time.
As you can imagine the reaction from our group about engine braking, heel &
toeing, being in the correct gear for accelerating after the braking
manouvre, raged to the extent that the police instructor got hot under the
collar and started muttering about how poor professional racing drivers were
at normal driving.
With modern brakes there probably is not the need to change down - but to
many it feels lazy and we prefer to be more involved with our driving.
Certainly when it comes to poor conditions (ice, snow, other slippery
conditions) the use of gears to aid slowing and avoiding sudden large ratio
changes is much more beneficial. At which point habitual changing from top
to second may cause some interesting moments.
Cheers
Tony
> > >Suppose you're approaching a turn (left in the UK, like a right turn in
> the
> > >US), you slow down, you start changing gear - you don't go 5-4-3-2- turn.
> Err - I do
> > >You don't have to,
> But I want to!
> > 'cos you're SLOWING DOWN, you go 5-2-turn.
> [SNIP]
> With modern brakes there probably is not the need to change down - but to
> many it feels lazy and we prefer to be more involved with our driving.
> Certainly when it comes to poor conditions (ice, snow, other slippery
> conditions) the use of gears to aid slowing and avoiding sudden large ratio
> changes is much more beneficial. At which point habitual changing from top
> to second may cause some interesting moments.
What made the story interesting was that he told the police he had been
travelling in the opposite direction along the road to that which the
investigators deduced from the evidence: it appeared that he didn't want
his parents to know where he had spent the night!
I find it's normally better just to use the brakes to slow down in GPL,
as you can certainly spin if you change down too soon (eg. at La
Source).
There is one proviso: sometimes if you use engine braking it can be
easier to judge your speed - you just change down at certain points on
the track and you should slow down at the right rate for the corner. A
good example is the Nouveau Monde hairpin at Rouen, where you need to
change down to third just before the left-hander, then second just after
the apex, and you should slow down enough for the hairpin, but not so
much that you spin. I guess an expert could do it all on the brakes
anyway, but he would need to be a very good judge of speed.
At most corners you just hit the brakes at the right point and slow down
as quickly as possible, ie. you only need to avoid locking the wheels,
and engine braking is of no benefit at all, since the brakes are already
much better than the tyres.
Incidentally, most professional racing drivers are poor road drivers as
they always want to apply track/rally course methods to the road. It's
not for no reason that on a percentage basis racing drivers have more
accidents on public roads per mile driven than any other profession.
M
: I find it's normally better just to use the brakes to slow down in GPL,
: as you can certainly spin if you change down too soon (eg. at La
: Source).
Well, remember the engine is only connected to the REAR wheels in GPL
unlike modern road cars where engine braking would usually be FRONT
wheels only. I had a play with "rear wheel only" braking in
GPL the other day to see if it would help my braking technique.
(When rear wheel braking you _really_ don't want to lock up so you have
to pay MUCH more attention). Major kudos to anyone who can safely
negotiate parabolica from flat out with no front brakes because I
certainly can't. I gave it up as impossible in the end (but I'm not
that good a driver). Not tried it but I _think_ front wheels only
braking would be easier.
--
Richard G. Clegg Only the mind is waving
Dept. of Mathematics (Network Control group) Uni. of York.
www: http://manor.york.ac.uk/top.html
