Originally Posted by
tankist
What about automobile tires? It is a known fact that under-inflated ones result in worse gas mileage.
Sure, under the car manufacturer's recommended inflation pressure, which they figured by using the weight of the vehicle, and how it affected the recommended tires. You know, the same way people on this thread have said you figure proper inflation pressure for bicycle tires.
So, if you go under the recommended pressure on car tires, you lose fuel efficiency. The recommended pressure for most cars, is under the maximum inflation pressure for the tire. So you haven't hit on any gotcha, with the exception of confirming what people who actually understand this issue have been saying, tire pressure is based on the weight the tire has to carry. It really is that simple.