At 30mm wide, I'd say a 23mm tire would look and perform the best; if you go wider you'll need more vertical space. If you currently have that available you'll be fine, though you'll get more side spray.
@withered_preacher 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.
At 30mm wide, I'd say a 23mm tire would look and perform the best; if you go wider you'll need more vertical space. If you currently have that available you'll be fine, though you'll get more side spray.