3 ms·

Okay, dumb question from someone who rides a bike but is not a "cyclist." Road bikes have a pretty high tire pressure, to the point that the tire itself basica

Okay, dumb question from someone who rides a bike but is not a "cyclist." Road bikes have a pretty high tire pressure, to the point that the tire itself basically offers no cushion at all, on it's own. Why are these tires pneumatic at all? Why not wrap a rubber donut around the rim and call it a day? I'm sure part of the answer is weight, but surely this can be reduced either by making the rubber relatively thin, or using some sort of hard closed-cell foam underneath the rubber layer?

recursive 4y ago
Even at 100psi, there is significant cushioning behavior from a pneumatic tire for contact patches the size that road tires do.
spokeonawheel 4y ago
extra weight not ok
currency 4y ago
Solid tires crawl around the rim as you ride them. Okay for very low speeds; not okay for cycling speeds.
- glitchc 4y ago
  Bingo! That's the main reason why. Compressibility of the tire turns rolling friction into a translational force. Pneumatic tires also experience a translational force that tries to push the tire back and off the rim as it interacts with the ground.
deleted 4y ago
[deleted]
deleted 4y ago
[deleted]
thesausageking 4y ago
They exist and are called "airless tires". Tannus is one of the most popular brands: https://tannusamerica.com/pages/tannus-airless-tires https://tannusamerica.com/pages/tannus-airless-tires They're solid foam and can't go flat. They're not very popular because they don't perform nearly as well as tires with tubes. They have a higher rolling resistance (ie, you have to pedal harder to go the same speed) and have a rougher ride. Good quality tires don't puncture that often and, for most riders, are worth the trade off.
et-al 4y ago
In case you don't know, you probably don't need to pump your tire up to the stated pressure on the side of it. Check out these guides for more specific numbers, but generally if you're ~160lbs, you can get away with 80psi or lower when running tires wider than 25mm. https://silca.cc/pages/sppc-form https://silca.cc/pages/sppc-form https://axs.sram.com/guides/tire/pressure https://axs.sram.com/guides/tire/pressure
deleted 4y ago
[deleted]

recursive 4y ago

Even at 100psi, there is significant cushioning behavior from a pneumatic tire for contact patches the size that road tires do.

spokeonawheel 4y ago

extra weight not ok

currency 4y ago

Solid tires crawl around the rim as you ride them. Okay for very low speeds; not okay for cycling speeds.

glitchc 4y ago
Bingo! That's the main reason why. Compressibility of the tire turns rolling friction into a translational force. Pneumatic tires also experience a translational force that tries to push the tire back and off the rim as it interacts with the ground.

deleted 4y ago

[deleted]

deleted 4y ago

[deleted]

thesausageking 4y ago

They exist and are called "airless tires". Tannus is one of the most popular brands: https://tannusamerica.com/pages/tannus-airless-tires https://tannusamerica.com/pages/tannus-airless-tires They're solid foam and can't go flat. They're not very popular because they don't perform nearly as well as tires with tubes. They have a higher rolling resistance (ie, you have to pedal harder to go the same speed) and have a rougher ride. Good quality tires don't puncture that often and, for most riders, are worth the trade off.

et-al 4y ago

In case you don't know, you probably don't need to pump your tire up to the stated pressure on the side of it. Check out these guides for more specific numbers, but generally if you're ~160lbs, you can get away with 80psi or lower when running tires wider than 25mm. https://silca.cc/pages/sppc-form https://silca.cc/pages/sppc-form https://axs.sram.com/guides/tire/pressure https://axs.sram.com/guides/tire/pressure

deleted 4y ago

[deleted]