i'm doing a lot of research in anticipation of puting a bike together. i'm on the lookout for an old twenty that i plan to customize heavily. i ride a fixed gear conversion right now, and i plan to ride the twenty fixed too. on my current bike i love the speed and agility of the skinny wheels/tires and i'd like to go as skinny as i can with the tire for this folder. of course the 20x1 1/8" size would be the skinniest (451mm) but do you think i'd run into problems eventually with the availablility of tubes and tires? is that size in danger of obsolesence? i see a good deal of skinny tires on bikes here, what sizes are you guys pushing?