Sizing Relative to Mountain Bike

[bh357]

How would I size myself for a cross bike? My mountain bike has an effective top tube of 24" (609.4mm), and I'm running a 105mm (-10deg) stem, for a reach of about 715mm. My seat tube is 17.5", and I run my saddle a bit over 29" (from the bb spindle). Ground to stem clamp center is about 39". It's a 29er, and I'm running On-One Mary bars. This bike is an excellent fit for me.

The bike I'm considering is a Bianchi San Jose.

This bike would be mainly used for dirt road duty, but I'm probably going to be giving the "half hour suffer-fests" a go next fall/winter.

Thanks,
bh357

[flargle]

http://zinncycles.com/FitIntro.aspx
http://zinncycles.com/fitsystems/DimensionPage.aspx

Based on your saddle height, the 55 looks like the right size for you on the San Jose. But I would go through Zinn's sizing tool. Follow the measurement instructions very closely.