They run slightly big, but not drastically. I'm 6'1" with a 34" inseam and a 57 fits nicely. I generally prefer smaller frames to larger frames if I'm between sizes. After test riding a schwinn, a fuji, a surly, an iro, a giant, and a raleigh, the only bike that rode as nicely as the tt was the surly. After replacing my bars, pedals, and saddle, my tt feels about like the surly did. I was surprised with how rickety some of the other rides I tried out felt!