54 vs 56 Effect of sizing on handling, comfort, etc.

I'm bike shopping again looking at a 54 vs a 56 frame (same model). Since the difference in the top tube, reach, wheel base is only approx 2 cm, I can make both fit me. I'm leaning towards the 54 - because of a shoulder injury that affect my comfotable reach. My question is this...

If I went with the 54 but made up the differnce by:

a) adding 2 cm of setback on the seat (post or positioning on the rails)
b) adding 2 cm with a longer stem
c) splitting the differnce (1 cm seat and 1 cm stem)

What are the affects on comfort or handling for climbs, corners vs. having the extra 2 cm in the frame?

Thanks!

Personally I like the smallest frame that I can comfortably ride and that has more to do with effective top tube length than pure frame size. Smaller frames feel more responsive under me and I don't feel like I'm way up in the air. It's probably all in my mind but I just enjoy slightly smaller frames. I ride with 12 to 14mm stems on most of my bikes. The larger frames I've owned where I can get away with 10cm or shorter stems always felt awfully tall and the stems felt awfully short. If you can't get the effective top tube length to work without a setback seatpost then I would go with the larger frame option.

Bikes are designed with some implicit assumptions about how your weight is distributed between the front and back wheels, using a large seat setback to achieve effective top tube length changes that relationship. Similarly using a fast forward style TT seatpost puts more weight on the front wheel which can mess with handling.

Anyway, I'd go with the smaller frame if you can do so with a stem of 13cm or less and the seat on a stock seatpost. If that's still too short I'd go with a larger frame.

Just my 2 cents worth....YMMV,
-Dave

I am with Daveryan on this. Setback on the seatpost is not the way to make the smaller frame fit. The saddle fore-aft is dependent on the relationship between you and the pedals. Whether you need a setback seatpost or not is independent of the top tube length of the bike. 2cm is not a big deal for stem length difference and whether the 54 or 56 is better for you probably depends more on the head tube length and whether you like the bike to feel "small" underneath you.