I had less than a MM of clearance before. A coworker of mine tried to put a sheet of 20lb paper between the wheel and the fork this morning... He couldn't, because there wasn't enough room. I'm going to make the cutout in the very top of the tube a little deeper, so the wheel doesn't remind me of The Triplets of Belleville every time that I ride it. I swear last night that when I was at the right cadence, I heard his grandmother's whistle. Exact same timber and pitch, though quieter...