How long of a ride? For anything longer than 4-5 miles, I find jeans to be pretty uncomfortable. I often bike in athletic shorts (tights underneath in the winter) and change at my destination. I have found lightweight "hiking" pants to be more comfortable than jeans, and some khakis work well too. I think it's due to the thinner fabrics, which make for thinner seams, so less material to cause chaffing.