In case no one mentioned this, try a Panaracer Schrader-Valve/Presta-Valve Nut, Quality Part Number TU6000.
Look at the picture in Quality's Catalog at your LBS.
On a schrader sized hole, this nut threads onto the Presta Valve (if it is a threaded valve) and has a shoulder that faces down to fill the excess hole size.
Turn it over if using with a presta sized hole.
Al Petri, Jr.
> Till this summer, I had routinely just ridden with presta tubes in
> Schraeder-valve rims, w/o problems. This summer I broke down and
> bought a new pump head (Silca), which actually grips the valve, and
> pulled out two valves while removing the pump head. For us
> bottom-feeders, this is almost major, and we certainly aren't going to
> either use Schraeders or abandon the rims. I have found that some
> RadioShack rubber grommets designed to keep wires from fraying their
> insulation when they pass through metal chassis work fine as adapters.
> Little tight setting, but some "303" rubber protector from REI did fine
> to lube the rubber - and the tube for first insertion. This is hardly
> original with me, but I'll call it "research" instead of "plagiarism"
> since I've taken ideas from lots of people instead of just one... Maybe
> it will help you. Maybe you have found a better way; love to hear about
it.
>
> harvey sachs
> mcLean va