I have this bike and it has 700x38 tires on it. The rims and tires and everything is stock except for the saddle. 80% of the riding that I do is on the road and the rest is on rail-trail gravel paths. What I'd like to do is find a narrower tire to put on my rims to decrease the rolling resistance and make the road riding easier and faster. I want to keep my so that i can easily switch the tires back if I want to go on a gravel path.
With my current setup, what is the narrowest tire that I can put on my Cypress?