Originally Posted by
Will Goes Boing
At 5'8, a 54 is the right size for you. Since you're new to riding the bike is going to feel like a torture rack.... there's just no way around it. Assuming that you didn't cut the steerer tube, do you have all the spacers under the stem and have the stem at a positive angle?
If you do, and it's still uncomfortable, you just have to keep riding more until your body gets use to it. Road bikes are made to go fast, not made to be comfortable.
I'm not that new to riding... I'm on my third season riding and have several thousand km's on the bike now and have experimented with all kinds of saddle, stem and handlebar positions to try and find something more comfortable.
As for a 54cm being right for me, I think there is more to frame size than just how tall you are. I think I may have slightly shorter arms/legs compared to the average 5'8 person. I tried my cousin's 52cm Allez and it felt SO much more comfortable to me.