RE: Double (de-)Clutching

["Weiss, Jeffrey" <jeffrey.weiss@domain.elided>]

David H Willis and Associates Limited write:
> Double (de-)clutching on the downshift, also spins up the input to the
> transmission before shifting, to save a little on the syncros, but at
> least double the wear on the clutch

"At least" double the wear?  Well, I guess the bearing sees exactly
double the wear.  But isn't it usually the friction surfaces that are
the first to go in a clutch?  Since the second clutch/declutch cycle
involves only the transmission side input shaft (gearshift is in
neutral), I would expect the friction surfaces to see only a modest
fraction of increased wear.  No?
 
> Fred is again correct, of course, about upshifting. The engine will
> begin slowing when unloaded by the depressed clutch. And the
> transmission input will slow when you shift to the higher gear. The
> match will be better than if you spun them both up in neutral 
> by double (de-)clutching.

As I understand it from this discussion, when you double an upshift,
you don't blip to spin the transmission up.  In fact, you let the
engine drag the input shaft down since the engine de-revs faster
than the input shaft does.
--
jw
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