Can't decide between size 54 and 56

Usually if Trek's chart shows a size - that's a suitable size for using Trek's bikes. Have you tried riding both of them just to feel the difference? 54 might be not very comfortable for you I think. I'd suggest you go with 56 but you should test them out in practice. Just in case.

dannydan said:

Thoughts?

What position do you prefer on the bike. You say you like 'comfort', but that's kind of meaningless as a well fit racer's bike is as comfortable as a sportive or tourist's frame is to their riders.

Buy by how the frame fits your preferred position as the seat can be raised or lowered to fit. Top tube length/stem length and head tube height/spacers under the stem matter. 'Comfort' might be found in the shorter top tube and shorter stem with spacers under the shorter head tube. 'Comfort' might be found in stretching out with the longer top tube and longer stem with no spacers under the stem...or a stack of spacers under the stem.

And why the concern about swapping out for a longer/shorter stem? There's absolutely no guarantee either frame size and factory stem length combination is going to fit you. There is also absolutely no sense in spending big bucks for a new bike and not spending $50-$100 more to dial in a perfect fit.

And the 54-56 break point is usually where 170 and 172.5 crank arm length change occurs. Check to see what they are spec'd with and which works for you.

Test ride. And test ride again. You can not be made to fit the bike. The bike, however, can be made to fit you.

For performance the smaller bike is usually preferable. For comfort the larger; as long as the reach and the crank throw are not uncomfortable.