Can it be done? I have a spare rear wheel that takes the Schrader (car) valve, but I'd like to use it with a Presta tube. Bike uses Presta valve on the front wheel and I don't want to end up having to stock / carry round 2 tube types). Currently, the Presta rattles around in the hole when offered up, and when I tried inflating it a little, the valve protrudes through the hole so that it won't seat, even when the lock ring is wound right down to the base of the valve. Is there an adapter that will reduce a Schrader hole to take a Presta valve, or is it a no-go?