Back in my upright-riding days, I had a mountain bike that I sometimes used for club rides. It had slicks, and no shocks. I knew it was a little bit slower, but I didn't mind. Then I got the brilliant idea of riding it on a tour. You know, just in case there was rough pavement. Worst mistake of my life! Yeah, I lost 3 mph average speed; but the biggie was, I was completely drained, with 4 more days' of riding to do! I called my wife and had her bring me my road bike.