Heh, well thin tires are lighter, accelerate better, and have less rolling friction.
Alas, that's only true on perfect roads. Even normal road texture on asphalt and cement is enough to lose a fair amount of energy causing vibrations (which is after all a cyclic acceleration) in the bike and rider.
I've ridden 125 psi racing tires on a racing bike and noticed that I was noticeably faster (on the speedo) when riding a painted line than on the asphalt. When riding a gentle slope along a river it was quite apparent as I switched back and forth. It was also much quieter. I also trained with my racing team occasionally with my mtb with slicks and clipless pedals, no such difference at 60psi and 1.8" tires.
So it turns out that wider tires allow lower pressures, which are better at absorbing vibrations and allowing most of the energy to return. A compressed tire causes some heat, which some of which is released into the environment, but some also goes back into forward motion as the tire expands again.
So the ideal inflation changes with the roughness of the surface.
A relatively recent development is improvements in material science that allows for wider rims with a smaller weight penalty and lighter tires. Lower pressures also help lower the weight of the tires/rims (less force) and wider tires generally give more protection to the rims, allowing the rims to be lighter. Tubeless also has been a big help, less weight, less internal friction, and more compatible with the wider tires which have higher volumes and lower pressures.
So 10 years ago 50% wider tires/rims had a significant weight penalty, not so much today. So in every biking segment from weight sensitive racing bikes to various flavors of mountain bikes are going wider. A decade ago 1.95-2.1" mtb tires were the most common. Today it's 2.35-2.6", which is a bit deceiving. Tire width for the same performance decreases with diameter. 10 years ago 26" was the most common, today the large majority of decent mountain bikes (say over $1000 for a hard tail or $1500 for a dual suspension) are 27.5" or 29".
So the air in a 27.5" x 2.6" tire is significantly more than the old 26" x 1.95".
Also, humans frankly stink as an engine, and are VERY susceptible to vibration, rpm, temperature, comfort, etc. So unlike a car where comfort isn't directly related to performance, on a bike a happier rider = riding faster and longer. So being 10% more comfortable can lead to real performance gains, and high pressure tires can be very uncomfortable, even to the point of numbness.
So now even road bikes that claim to be the world's most efficient bikes, fastest for a given rider input, are having ever wider tires. People are realizing even at the highest levels of racing a few more mm and a few less PSI can lead to faster race times.
Alas, that's only true on perfect roads. Even normal road texture on asphalt and cement is enough to lose a fair amount of energy causing vibrations (which is after all a cyclic acceleration) in the bike and rider.
I've ridden 125 psi racing tires on a racing bike and noticed that I was noticeably faster (on the speedo) when riding a painted line than on the asphalt. When riding a gentle slope along a river it was quite apparent as I switched back and forth. It was also much quieter. I also trained with my racing team occasionally with my mtb with slicks and clipless pedals, no such difference at 60psi and 1.8" tires.
So it turns out that wider tires allow lower pressures, which are better at absorbing vibrations and allowing most of the energy to return. A compressed tire causes some heat, which some of which is released into the environment, but some also goes back into forward motion as the tire expands again.
So the ideal inflation changes with the roughness of the surface.
A relatively recent development is improvements in material science that allows for wider rims with a smaller weight penalty and lighter tires. Lower pressures also help lower the weight of the tires/rims (less force) and wider tires generally give more protection to the rims, allowing the rims to be lighter. Tubeless also has been a big help, less weight, less internal friction, and more compatible with the wider tires which have higher volumes and lower pressures.
So 10 years ago 50% wider tires/rims had a significant weight penalty, not so much today. So in every biking segment from weight sensitive racing bikes to various flavors of mountain bikes are going wider. A decade ago 1.95-2.1" mtb tires were the most common. Today it's 2.35-2.6", which is a bit deceiving. Tire width for the same performance decreases with diameter. 10 years ago 26" was the most common, today the large majority of decent mountain bikes (say over $1000 for a hard tail or $1500 for a dual suspension) are 27.5" or 29".
So the air in a 27.5" x 2.6" tire is significantly more than the old 26" x 1.95".
Also, humans frankly stink as an engine, and are VERY susceptible to vibration, rpm, temperature, comfort, etc. So unlike a car where comfort isn't directly related to performance, on a bike a happier rider = riding faster and longer. So being 10% more comfortable can lead to real performance gains, and high pressure tires can be very uncomfortable, even to the point of numbness.
So now even road bikes that claim to be the world's most efficient bikes, fastest for a given rider input, are having ever wider tires. People are realizing even at the highest levels of racing a few more mm and a few less PSI can lead to faster race times.