It does look small, doesn't it?! The guy who built it changed the frame and did LOTS of other custom work on it. (It's actually really fun to click on the "yangyang" link on that post about Alex, to see the whole history of the bike.)
I wonder if Alex was surprised that the bike was so low to the ground, when it was delivered...

But then again, a guy with really long legs is bound to run into that. Remember when he wasn't able to ride one of the bikes they brought in for him to use in that scene where Steve rode the bike through the bar doors and up the stairs?
