Originally Posted by
crhilton
That sounds like a good way to destroy a rim.
Why? I wouldn't think that another valve hole 180 degrees away would cause any real trouble. I've drilled mine out for schraeder, and even when I had the original total crap single walled rims drilled for schrader, riding on roads that are so rough that eventually I broke an axle, the cheapo rim never failed. With a good rim I wouldn't think this would really cause any trouble.
As for riding with the extra stuff inside, shouldn't be a problem. Heck, I rode all last winter with my Nokians pushing studs in towards the tube, so I cut the beads off an old tire and used it as a tire liner, riding the whole winter with the extra tire stuffed in there.
I might be leery of drilling an extra hole with really narrow rims, but I'm not a speedster anyway, and I wouldn't ride my route with anything skinnier than 32s.
This is actually a pretty intriguing idea. I'd probably do it but I get less than one flat a year.