Originally Posted by Grasschopper
The top tube lengths seem WAY longer than roadie TT numbers so it is throwing me off a bit.
Are you looking at the ACTUAL top tube lengths or the THEORETICAL top tube lengths? Since the TTs on mountain bikes are more sloped than on road bikes, they're going to be longer. When sizing, you want to compare theoretical top tube length, meaning the lenght of an imaginary line, parallel with the ground, from the center of the seatpost to the center of the head tube where it meets the top tube.