My ride home last evening was much easier than the ride out. I was carrying less weight in my backpack (though still around 15lbs or so), had eaten something, and tightened the rear shocks up. And I noticed during the ride home that the rear tire would occasionally slip out of the dropout slightly and rotate sideways about 25 degrees, such that the edge of the tire would rub against the frame of the bike. Surprise, losing half of your energy to friction really makes a difference. Correcting this made the ride much easier. Though I’m still going to stick to the car for now: externalities aside, oil is just so much cheaper than food, and I’m lazy.