Just this last week I put new tires - Kenda Kross Plus - new cassette, and new chain on my Trek 820. It really needed them. Last night I took a 12 mile ride around the 'hood to make sure everything was working properly.
Today, I took a 38 mile ride on the Katy Trail which is flat and topped with crushed stone. I really noticed how much more uncomfortable this bike is for these kinds of rides than my Raleigh hybrid. The Trek has me leaning forward with much more of my weight on the handlebars, and after a couple of hours it got uncomfortable. I can easily do 50+ miles on the Raleigh and feel fine. I usually use the Trek for 10-15 mile rides around home on gravel and some pavement.
Maybe it was the heat, but I don't think I will repeat that kind of a ride on the Trek soon.