Wasn't the thing with the second hole for a valve in a rim a trick for some racers (probably MTB) in order to carry a second tube in the tire for fast repair in case of a puncture. You just had to inflate the spare tire and go one riding. I do not recall where i read this but could have been on this list.
Michael Schmid Oberammergau Germany
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-----Ursprüngliche Nachricht----- Von: email@example.com [mailto:firstname.lastname@example.org] Im Auftrag von John Betmanis Gesendet: Mittwoch, 3. Dezember 2008 17:50 An: email@example.com Betreff: RE: [CR]Wheelbuilding Questions - valve stem holes
At 10:27 AM 03/12/2008 -0600, John Hurley wrote:
>One interesting thought
>regarding valve stem holes was that you can always turn a Schrader rim
>into a Presta rim by simply drilling a second hole. I'm not convinced,
>however, that a Presta valve would mind using an oversized hole instead
>of the usual 6mm.
Wasn't the original question whether a Presta hole cam be drilled out fot a Schrader valve? Of course it can, if you're careful. Best done in a drill press. You don't want the drill to grab or end up with a 5-sided hole. My question would be, why would you want to use a Schrader valve tube? Most on-topic good quality vintage bikes used Presta valves. To this day, Schrader valves are only found on mountain bikes, children's bikes and department store bikes.
As for using a Presta valve in a Schrader hole, I too doubt if it would be a problem in the real world, although it wouldn't look "right". There are bushings and grommets available to take up the gap. I certainly wouldn't drill a second hole. Personally, I'd make a couple of aluminum bushings with a thin flange on the inside of the rim. I don't usually use them, but a nut on the outside would hide any evidence of the bushing.