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wider tires also let you run lower pressures, which puts you more in the comfort zone of being able to convert to tubeless. not every rim/tire combination work

by durkie 5y ago

wider tires also let you run lower pressures, which puts you more in the comfort zone of being able to convert to tubeless. not every rim/tire combination works with tubeless, but if you are able to pull it off, it's among my personal top 5 list of cycling innovations of the past 30 years.

wolverine876 5y ago
I'm missing something: How do lower pressures lead to tubeless?
- davisoneee 5y ago
  Narrow tyres tubeless is a no-go as the high-psi required to get the tyre seated and shaped can cause blowouts, especially if you get impact such as a pothole. Going for wider tyres means you naturally can go lower PSI, but if you drop PSI with tubes you risk pinch-flats ('snakebites'), where striking a hard edge causes both edges of the tyre to puncture (like X___X on the cross section, rather than \__x_/ of a normal puncture). If you go wide, you can then drop the pressure more as you don't have a tube to pinch. This gives you the great comfort, the pliability to absorb road imperfection (which improves speed), and less likelihood of puncture. As an approximate pressure guide: # weight in kg. front load probably 0.45 (45%). tyre width in mm weight_front = weight * front_wheel_load weight_rear = weight * (1 - front_wheel_load) psi_front = (338.14 * weight_front / tyre_width ** 1.5785) - 7.1685 psi_rear = (338.14 * weight_rear / tyre_width ** 1.5785) - 7.1685 This should ballpark you 15% tyre deflection under load, which was a guide from an old bike magazine on a balance of rolling resistance and comfort.
- deleted 5y ago
  [deleted]
- durkie 5y ago
  'davisoneee covered it pretty well, but mostly lower pressures mean it's less of a pressure differential that the sealant has to withstand. "Road tubeless" setups exist for narrower tires, but a lot of them have upper pressure limits around 80 psi / 5.4 bar. Running wider tires / lower pressures gives you a bit more margin of error.
- et-al 5y ago
  Folks want to run tires at lower pressures, but this increases the risk of pinch flats for inner tubes when the rim bottoms out against the ground. Tubeless setups don't have this risk.
  - sliken 5y ago
    Yes, a bit, but you won't want to ever bottom out, with or without tubes. You can snake bite flat tubeless, you can also damage the rim. Generally you want enough air pressure to have enough air pressure to have a 10-15% deflection in the tire and never bottom out. Thankfully suspensions help with the pinch flat since they basically time average the impacts.

by durkie 5y ago

wolverine876 5y ago

I'm missing something: How do lower pressures lead to tubeless?

davisoneee 5y ago
Narrow tyres tubeless is a no-go as the high-psi required to get the tyre seated and shaped can cause blowouts, especially if you get impact such as a pothole. Going for wider tyres means you naturally can go lower PSI, but if you drop PSI with tubes you risk pinch-flats ('snakebites'), where striking a hard edge causes both edges of the tyre to puncture (like X___X on the cross section, rather than \__x_/ of a normal puncture). If you go wide, you can then drop the pressure more as you don't have a tube to pinch. This gives you the great comfort, the pliability to absorb road imperfection (which improves speed), and less likelihood of puncture. As an approximate pressure guide: # weight in kg. front load probably 0.45 (45%). tyre width in mm weight_front = weight * front_wheel_load weight_rear = weight * (1 - front_wheel_load) psi_front = (338.14 * weight_front / tyre_width ** 1.5785) - 7.1685 psi_rear = (338.14 * weight_rear / tyre_width ** 1.5785) - 7.1685 This should ballpark you 15% tyre deflection under load, which was a guide from an old bike magazine on a balance of rolling resistance and comfort.
deleted 5y ago
[deleted]
durkie 5y ago
'davisoneee covered it pretty well, but mostly lower pressures mean it's less of a pressure differential that the sealant has to withstand. "Road tubeless" setups exist for narrower tires, but a lot of them have upper pressure limits around 80 psi / 5.4 bar. Running wider tires / lower pressures gives you a bit more margin of error.
et-al 5y ago
Folks want to run tires at lower pressures, but this increases the risk of pinch flats for inner tubes when the rim bottoms out against the ground. Tubeless setups don't have this risk.
- sliken 5y ago
  Yes, a bit, but you won't want to ever bottom out, with or without tubes. You can snake bite flat tubeless, you can also damage the rim. Generally you want enough air pressure to have enough air pressure to have a 10-15% deflection in the tire and never bottom out. Thankfully suspensions help with the pinch flat since they basically time average the impacts.