See Sheldon for a good rule of thumb as to what width of tyre will fit on what width of rim: http://www.sheldonbrown.com/tire-sizing.html#width
@Bearlegged started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
See Sheldon for a good rule of thumb as to what width of tyre will fit on what width of rim:
http://www.sheldonbrown.com/tire-sizing.html#width