I've only limited experience, but
Univega Super Special - 25 with fenders easy.
Trek 400T - 28 with fenders no problem.
Pinarello Record - don't even think about it even with 700x18 (edit: actually, if I replaced the fork I could probably run fenders front and back with some 23s.)
Last edited by LesterOfPuppets; 11-08-10 at 04:30 PM.