On Sat, 14 Oct 2006 02:22:32 GMT, "Leo Lichtman"
wrote:


wrote: Push the tube against the base of the tire
valve to provide resistance: (clip)
^^^^^^^^^^^^^^^^^
The first thing I would do is try it on the other tire (that is still
inflated) to make sure it is working okay. Presta stems usually are held to
the rim by a nut, so when you apply the connector, the stem is firm. With
the tube off the rim, I'll bet you are not inserting it far enough to
actuate the mysterious linkage to close off the Shraeder opening. This is
consistent with what Carl V. said.

Dear Leo,

Sorry, I wasn't clear--the idea is to seal the base of the Schrader or
Presta valve and provide back pressure.

Twin-head air chucks work by air resistance. If there's not enough
back pressure to trip the valve (an empty inner tube), the wrong
outlet may stay stubbornly open.

Usually, pressing the tire and tube flat against the base of the valve
provides enough back pressure to trip the annoying valve and make it
notice which outlet you want to use.

Ryan Cousineau explained this gentle push-the-tube-against-the-base
trick that provides back pressure and cured me of my more enjoyable
habit of giving the recalcitrant twin-head chuck a brisk whap with the
handiest tool to wake it up.

Cheers,

Carl Fogel