Re: [CR] tire pressure gauge sought

(Example: History:Ted Ernst)

From: "David Snyder" <dddd@pacbell.net>
To: <classicrendezvous@bikelist.org>
References: <848103.57590.qm@web50502.mail.re2.yahoo.com> <E52AE664-A0ED-444F-A81B-2904BE06555F@pt.lu> <8CCBA1713BCDAF5-7E4-471E@webmail-m095.sysops.aol.com> <F9B5ABF2-8A13-4F6D-994A-7634ED2D677E@pt.lu>
In-Reply-To:
Date: Wed, 5 May 2010 17:08:32 -0700
Subject: Re: [CR] tire pressure gauge sought


Various Presta heads (chucks) that I encounter "in the field" often have sealing issues.

What I've noticed is that many, if not most Presta heads are designed specifically to fit only onto the minor-diameter threaded portion of a Presta valve. This requires a delicate touch while fitting the chuck.

Once they've been forced onto the major diameter (threaded or un-threaded) portion of the Presta stem, they may no longer give a tight seal on the smaller threads (which the valve's plastic cap threads onto). This applies to both "push-on" and "locking" presta heads.

With use and/or age, most Presta chuck washers seem to suffer this fate. One byproduct of this is that for a given level of sealing power (read p.s.i.), the chuck will require much more force to remove from the larger of the two outside-diameter portions of the stem, doubly stressing the tube's rubber where it's bonded to the stem metal.

For this reason, I am reluctant to let others use my presta chucked air pumps. I myself get years of service out of properly-used presta chuck rubber inserts of all types. When using "shared" pumps, I never know what to expect.

I really don't use guages at all except to check the function (accuracy) of my floor pump's guage. Using the pump as a guage (requires making one stroke to pop the valve open) allows me to simultaneously add whatever pressure is needed even if the tire was pumped just one day earlier.

Positioning the wheel so the Presta stem is at the 12-0-clock position goes far in preventing any air loss during chuck removal, and is virtually required with valve-less frame pumps such as the typical Primus or Silca in order to prevent violent blowback/kickback. Keeping the pump head straight on the valve also improves (prevents interference with) the (gravity-assisted) self-sealing action of the valve core.

David Snyder using the dinky plastic "over&under" style twinhead in Auburn, CA usa

Dale Brown wrote:
> <<.. I bought a french Lezyne classic floor >>
>
> French?... ... Barrel and handle are very nice. Chuck is not up to old
> Silca I'm afraid.