Looked at cannondale adventure bike today a 12 and 13 in the range of $500. One has larger tires than the other......what's the difference between them. I ride mostly crushed gravel, some paved and not to far ,40 miles several times a week. I'm going to look at Trek @ the end of the week.

What's a good entry level bike for under $600. I don't know enough about which derailer is better than another to really know the difference or any other part for that matter.