The Surly Thing

[wildeny]

Hello, Sue, I never ride a Surly but I'm about the same height as you so I just speak from my experience of picking a bike.

Short answer: pick up Surly 42 cm

Long answer: Look at the effective top tube length and the stand over height. These two are the limiting parameters for petite women to pick up a road bike.

Surly 42cm has a TT (Effec.) 522mm, which is already in the long side and even longer than Specialized 49 cm (vs 515mm -- this one is OK).
As for the stand over height, it should be equal or less than your inseam measured without shoes on (which will be your margin).

I estimated that your inseam is about 727 mm (by this formula "height/2/1.1" for normal people), while SO height is 732 mm in Surly 42cm and 748 mm in Specialized 49cm. I'm not sure about whether you wore the shoes or not when testing Specialized.

I wouldn't choose either if it's higher than my inseam. That's why I chose Fuji Finest RC XS instead of Fuji Roubaix Pro 49cm. With my shoes on, I have few cm for clearance on Finest RC XS (however I'd prefer shorter top tube length, say 500mm instead of 515mm).