What's the inner width of my rim?
Nashbar's specs for the rim list the inner width as 16mm.
http://www.nashbar.com/bikes/Product_10053_10052_566766_-1___
(click the "Specs" link)

This is a fairly standard width for road wheels, so you should be able to safely run any common road tire size (21mm-35mm give or take a few mm).