Originally Posted by old and new
Judging by what YOU have stated,back probs., being new ,dirt history, dirt future..Where's the choice?
Specialized Tricross pretty much defines your requirements. The others are road bikes,OK they would work but comin' -off a mountain bike I guess you would "feel" the cross really well. It has a triple. Ok let's hear the debates....
I am a mountain biker and got a road bike last year. Your worry about the tyre size need not be a problem. I went from wide knobblies with suspension to 26 tyres and found just a bit of a problem and that was in the wheels. They were radial spoked and were a bit harsh. Got a new set of wheels that had the spokes crossed x2 and wnt to a 23 tyre. That is comfort. Just stay off the radial spoked wheels and the tyre size is immaterial.
If you asked me for a choice of bike to go for- and I researched the options pretty well- I would go for the speccy Sirrus. A good road bike with straight bars. I went for a road bike but If you have a back problem- and coming off a mountain bike- I would stay off the drop bars.