"Tim+" wrote in message
...
I defy most drivers to be able *reliably* to change gear without using
that
pedal that "doesn't appear to [do] much" ;-) Some cars are better than
others for doing clutchless gearchanges: my 13-year old Peugeot is dead
easy, and I think it always has been fairly easy even from about 20,000
miles when I got it. But my wife's 5-year-old Honda is a lot more
fussy
about getting the speed very accurately the same - it is less
forgiving. I
never try a clutchless change while she's in the car ;-)

Why would you bother other than as a €œparty trick€�? Its not good for
your
synchromesh.

Its not bad for it either if you know how to match speeds

If you get it exactly right, I grant you its harmless but youre asking
your synchromesh to do a job it wasnt designed for. Do you always get it
*exactly* right?

It all depends on how good the baulk rings are and how much tolerance either
side of the matched speed they allow. I imagine that cars that are very
fussy about clutchless gearchange have very effective baulk rings which
prevent the synchromesh cones coming into contact until the speeds are very
closely matched, and make the characteristic graunching noise if the speeds
are not closely matched. That's good for the cones because there will be
very little rubbing at contact point. If the baulk rings are less effective,
they will allow contact when there is a greater disparity of speed, which
potentially puts a greater strain on the rings if you happen not to match
perfectly. OK, so you'd feel it as a sudden retardation or acceleration of
the car.

On my car I can usually change down OK, because you just increase the
throttle gradually until the gear slips in. I find changing up more
difficult for some reason, even though in theory it's just the same throttle
adjustment in the opposite direction.

Clutchless gearchanges aside, I always try to match my engine and road
speeds reasonably well - I've got to know roughly how much the rev counter
needle needs to move from its speed for the old gear when changing to a new
gear. At the very least, I keep the engine revs constant during the
gearchange, and preferably I actually change the engine revs the right
amount in the right direction. What I don't do is what some people do: let
the engine revs fall to idling, let the clutch up on the idling engine and
then reapply power (*). That causes horrendous lurches and must do horrible
things to the clutch which has to take the strain of the mismatch. I got a
lift with a woman who had been driving a few years longer than me but had
never learned about rev-matching. After she'd apologised for the n-th time
about her jerky gearchange, I rather diffidently suggested that there might
be a "different" (ie "better") way of doing it. She let me demonstrate and I
talked her through the process (which surprisingly difficult to analyse when
you do it subconsciouly). She was gobsmacked. Goodness knows whether her
instructor taught her badly or whether she'd slipped into bad habits
afterwards. I suspect the latter, because the gearchanges she was doing
would not have got her to pass the test.

It's a skill. No-one is born knowing how to do it. It takes a lot of
practice. The miracle is that having acquired the skill, it is transferrable
from one car to another and doesn't have to be re-learned to take into
account different clutch bite point, different responsiveness of throttle,
different spacing of gear ratios etc - it just requires a bit of mental and
muscle-memory tweaking of the parameters in the mental algorithm.


(*) The technique that was required for drivers of 1st generation DMU
trains, to allow time for several different gearboxes on engines along the
train all to change gear by remote (drive-by-wire?) control. I have "fond"
memories of the DMUs on the Aylesbury-Marylebone service in the 1970s and
80s which would accelerate hard in first gear after leaving a station, then
disengage and let the engine idle for what *seemed* like almost a minute
during which time the train not only stops accelerating but actually starts
to slow a bit, and then there was a sudden surge of power in the new gear.