RE: Reply to Double Clutching & What is it

[Todd Phenneger <zarati@dmi.net>]

Umm, I dont mean to gripe but I believe you are confusing double-clutching with "matching downshifts".  Your first statement seems right.  It was used to shift before synchros were used.  I have a friend with a Land Rover that Isn't syncroed in First gear so you have to do it to get into first while moving. 
	Anyhow, double clutching consists of depressing the clutch, shifting to nuetral, then releasing and re-depressing the cluch and then finishing your shift.  It is possable to match your RPM's and not even use the clutch but if you miss you get to listen to that oohh so awful sound of grinding gears hard.  
	Your description of matching downshifts was great but I believe that that is not double clutching.  

	Todd Phenneger
	84' 4kq
	zarati@dmi.net

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From: 	Adam D. Spiker[SMTP:facemate@juno.com]
Sent: 	Sunday,July 13,1997 1:14 PM
To: 	quattro@coimbra.ans.net
Cc: 	quattro-digest@coimbra.ans.net
Subject: 	Reply to Double Clutching & What is it

I am by no means a mechanic, but my dad used to race open-wheels and
taught me the artful precision to "double-clutching".  It was apparently
used to get into a lower gear before they had put sinchro's into gear
boxes or something like that.

At any rate, for what ever mechanical reason which prompted double
clutching, we are not bothered by it any longer.  The entire purpose of
d.c. is to maintain the ability to accelerate through and out of a turn,
and to use the natural friction of the engine to slow the vehicle AND NOT
THE BRAKES.  Often, you might see a sign which says NO ENGINE BRAKING as
a major road enters a residential area.

It is a simple demonstration in real life, but more lengthy to write
about.  But here it goes:

Example....	You are in third gear, approaching a turn which can be
taken at at least 25 mph.  There are no lights and no stop signs.  Let's
say that while in third and approaching, your running approximately 3000
rpm.  While pressing in the clutch and moving into second gear, you
simultaneously tap the throttle up to approximately 1000 rpm higher than
the gear you were just in (3000 rpm).  You then let out the clutch with
the car now in second, the rpm's matched to the speed that the wheels are
traveling and absolutely no clutch wear.

My dad always told me never to buy a manual transmission from a girl
because they surely slip the clutch.  However sexist this may sound it is
99.99% true.  This extends to about 70% of men as well.  Slipping is the
most damaging to a clutch.  This is when, during the same scenario as
above would not rev the engine up to speed and simply slip the clutch out
until the engine caught up to speed.  This is also the person who sits on
an incline and instead of using the brakes when he's stopped, he rides
the clutch to hold him still.

Double clutching/engine braking is what every professional racer and
"protector of the all expensive clutch repair" does.  It takes some
practice to learn your car's rpm's, but it will extend the life of your
clutch.  Hope this helps.  Again, I am not a mechanic but I have mastered
this process and am a firm believer in it.


Adam Spiker
FaceMate@Juno.com