[Sojourneyman]

I've got an 07 Fuji Roubaix that I was thinking about converting for cross season, which would be my first.

Considering the stuff I'd need to buy: Will I be fine if I do this by just getting new tires? Or are other, more expensive changes needed?

 

[d2p]

Most modern road bikes are set pretty tight and don't leave much space. Try mounting a cross tire on the front and see if you have any clearance.
Then imagine a little mud built up in there and see if the wheel will still turn.

I've tried to do the conversion several times and ended up frustrated.

Last time was a mid80s Trek road bike for my daughter. The bike had "some" clearance with a 28mm tufo until it picked up a little mud.

 

[Kram]

Even older "touring" frames don't have that much clearance. I have an old Gitane that I can get 30c Ritchies on with a little clearance but not a lot. But it will be my pit bike, so that's OK. Do you have an mtb? That would work better-just get some less aggressive tires and take off the bar ends if you have'em.

 

[Sojourneyman]

Dang, forgot to think about that. Maybe I'll look into moving bikes around and dropping my back-up bike for a cx bike