Current Projects chat and miscellany

I'd like to get as big tyres as possible on my roadie, would anyone like to hazard a guess if I could get anything larger than 28's in there? For reference there's 23's in there now and I have had 25's with guards in before.

http://i.imgur.com/b6Fv0O3.jpg

http://i.imgur.com/yRvK5O7.jpg

http://i.imgur.com/LIXVwoZ.jpg

I bet some 28c 4seasons would fit in there nicely, they fit in a Boardman