Re: [CR] Presta vs schrader extension of 700c vs 27''

(Example: Racing:Jean Robic)

From: "David Snyder" <dddd@pacbell.net>
To: <classicrendezvous@bikelist.org>
References: <4B3670C2.4080903@pacbell.net>
In-Reply-To: <4B3670C2.4080903@pacbell.net>
Date: Sat, 26 Dec 2009 16:45:45 -0800
Subject: Re: [CR] Presta vs schrader extension of 700c vs 27''


On the subject of drilling, I no longer shun the use of a home-drilled rim, as a Presta valve stem actually fits better in the bigger (~8.3mm) hole, and I often find good deals on classic rims that have been drilled this way. There's an enlarged O.D. at the base of a Presta valve that better sits within the rim's wall than atop of it, since the surrounding rubber is inevitably pushed down by pressure to the point of being flush against the inside of the rim. As well, the enlarged valve base keeps the Presta stem centered in any case. Almost all doublewall rims drilled for Presta already have an enlarged "inner" hole to accomodate the enlarged (8.3mm) base of a Presta valve, but oddly enough, singlewall rims drilled for Presta have only a 6mm hole (and thus don't allow the tube to sit flush with the inside of the rim where the valve enters). It seems this would encourage the valve being pulled free of the rubber, and I have had Presta stems pull free of a singlewall rim while pumping. The only caveat is that the enlarged hole should be free of sharp edges. Rim tape is too thick to allow the stem base to fit in the hole if the tape itself is only drilled large enough for the Presta stem(!), so the tape must be clear of the larger hole.

David Snyder
Auburn, CA usa


----- Original Message -----
From: Bob Freitas


> We redrilled many rims from Schrader to Presta (adding a Presta hole at

\r?\n> 90o as I recall)

\r?\n> BOB FREITAS

\r?\n> MILL VALLEY, CA USA