From Trek to Surly - advice on frame size I have a Trek FX7.3, frame size 22.5 inches. I'm looking to swap the frame out for a Surly Cross Check. Has anyone done a similar build? Also, what frame size would you recommend that I go for?

Just an idea at the moment - I'm not too sure how compatible more of my parts would be with the Cross Check frame.

Cheers!
You could compare the geometries of the FX and the Cross Check. Matching the standover, 56cm matches. Comparing the effective top tube lengths, between 58cm and 60cm match.

Bottom line the geometries are different.

On another note, the FX doesn't seem to be a particularly high-end bike, so purchasing a complete Surly could possibly provide more economical than moving the parts to a new frame.