Originally Posted by
autonomy
Bingo. IMO, if you're already moving, then you don't need to worry about acceleration all that much and air resistance is negligible given the surface area of your body plus your gear. But if you're working against a soft tire which is deflecting a lot, you're expending more energy to go the same speed. Yes, you can be fast on thick, flexible, or knobby tires, but the question is does it make you more tired in the end? A stiffer, thicker tire can ride as well or better than a soft, thinner - or underinflated - tire.
Actually, if using the same pressure, tires of identical size will have to deflect a roughly identical amount to create a contact patch the correct size to hold the same weight, so a tire with a thicker tread or casing or flat-resistant layer will almost definitely use more energy and give a rougher ride than a thinner more flexible tire.
Of course, if you are using lightweight tires and get seven flats per hundred km, you will be much more comfortable and less tired using a tire with flat protection, but for reasons other than 'ride quality'.