We use the Continental 4Season 700x28s. We're a heavy team (bike+riders=~500). We wear out (square off) rear tires in about 800 miles, so I'm slowly refining a rotation plan (new tire on front, front moves to rear, rear gets folded up and saved). I had trouble getting new tires for a little while, so I save the old rears in case we cut enough tires to exhaust our stash of new tires. I also keep the best of the old tires in our Trunkbag, so we have an on-the-road spare.