Help me build a cyclocross
 

What do I need to buy to make this into a decent cyclocross bike?

https://lh4.googleusercontent.com/-y...-27-22_420.jpg

easiest, +1, just buy another bike, Cross is a 'thing', now lots to choose from.

Your road bike lacks tire clearance for any but a groomed dry course.

Is that the distance between the ground and the crank?

Would it be easier to take moutian bike and build it into a cylocross bike. You would have more clearance on the rails for mud dirt and crud, still be pretty light with a alum hard tail and you could put a lighter fork on the front.

Or just by a new bike like a Soma double cross.

Your brake calipers can't accommodate
tires with the proper width for CXing.

So do I buy new brakes and tires and call it a day? The question I asked was what I should buy to do the conversion, not whether or not I should do it.

Sorry, I see that sounded like i was telling you to get another bike, I was actually asking for myself as i have several moutian bikes (older junkers) and one Giant road bike I could use some parts off of, I to am curous what it is that makes a cross bike?

A new frame (one with more clearance for at least 700 x 30 tires and disc or cantilever brake mounts/bosses), new brakes (either disc or cantilever), and some cross tires. Maybe a new cassette or chainrings, depending on the terrain.

Or if by some miracle you could fit 700 x 30 or larger cross tires without rubbing the chainstays, seatstays, or brake calipers, just buy the tires.