This is a 3 year old thread but I was curious what others do running presta tubes in a rim drilled for a schrader tube. There were some small gizmos mentioned in this thread that I had never seen like this one from mavic, http://www.sjscycles.co.uk/mavic-rim...esta-prod3335/

I've always just used a washer underneath the threaded nut on the presta tube.