Today we rode 37 miles and it felt more like 137 miles. I've ridden this route about 5-6 times and it always feels the same--sometimes a bit better and sometimes worse. Contrast that with a 70 mile route in a different area done a few days ago on Sunday that felt almost effortless (this route has been done many times and always feels easy). Really very disappointing and screws with my confidence that I was so exhausted after the ride, especially considering that I'm about to do an 80 mile ride this coming Saturday and the Hotter'N Hell 100 in a few weeks. Average speeds and weather conditions are very close to the same other than humidity which is a bit higher on the short rides. The hill peaks are generally higher than my 70 mile route and my average heart rate is around 15-20 bpm higher on the short route. Breakfast and fueling on ride are the same. The only difference is the dinner the night before the rides. 70 miler has a huge Mexican food meal with lots of chips, soapapillas and 3 beers. Short ride dinner is much lower calorie--about 700 vs 2000 or more for the grande feast. My buddy rides both rides with me and can't tell much of a difference. I suspect he might be riding well below his fitness level which may not manifest a big difference in perceived exertion like it does me. Any ideas?