In addition to the suggestion above- be sure the shorts fit correctly. I did a 60 mile ride in shorts that were too big, and I had some chaffing that made the last half of the ride and the next few dayas really uncomfortable, right under my sit bones). (I was losing weight and had "shrunk" out of my shorts and needed a smaller size).
+1. I think there's a rule of thumb that says to buy the smallest shorts you can fit into. There's some truth to that.