I am planing to beef up my '05 Trek 1000 tires in order to support a 300 mile ride on flat, crushed limestone terrain. What tires would work best for this? I am 230lbs/6'3". My rims are a stock Alexrims AT450. I was on this terrain this weekend with the default tires and they worked well. But I want to make sure if I hit some mud, the new tires can make it through. What are the 'knobbiest' tires I can use on this bike?