I am going to be commuting with a mtn bike, because I like riding upright and the wide tires. I still have the knobby tires that came with the bike. I would like to switch to smoother tread and am looking for suggestions.

I am concerned that I may lose traction during recreational rides on crushed limestone or dirt trails. Ultimately, I would like to have two sets of wheels that I can change as my needs change.

Anyone have a preferred tread for multi use?