Convert road bike to cross?

[Eden]

Absolutely. You can convert almost any bike into a track, fixie, or singlespeed...whatever your desire. The less vertical the rear dropout, the easier. Otherwise you'll need fashion some sort of chain tensioning pulley.

Perhaps, but you would have to be careful to confirm that it would be allowable for racing on the track.... they can be pretty strict about the equipment out there and its very much about safety. Anything that might cause a chain to slip or come off is very dangerous (thus no quick release wheels, etc.) I doubt any type of chain tensioner would be allowable period, though there is a special fixed speed hub ($160) that is supposed to work with non-vertical dropouts that might be OK - but its expensive... that $160 is just for the hub, you still have to get a wheel built around it. By the time you get the wheel built you might be able to find a whole used track bike for around the same price... ($300-$400 is typical)

Also everything (brakes, controllers, cables, derailleurs, 2nd chainring) would have to be stripped off the bike for the track season, so you'd need to redo all of it when cross comes back around. I suppose if you are careful you could reuse the cables and housings, but its very hard to do that.

I think it would probably be more economical in the end to look for 2 used bikes or rent at the track. Especially if you factor in the time and hassle of converting the bike twice a year. Some tracks (like ours out here) really want more women to participate, so rental bikes are free to them.