Why do car tires not need a tube or liquid sealant but bicycle tires do?
In: Engineering
Your premise is wrong.
The main way to lose air is spokes, the rest of the rim is basically equivalent between cars and bicycles.
Tubeless has been available on MTB and gravel rims for about 20 years now, and solidly the default for at least 10. You need rim tape, sealant, and tyres with the right kind of hooked bead, but it’s pretty trivial to set up.
On road bikes tubeless doesn’t work nearly as well because of the much higher pressures and smaller tyres. While MTB runs in the 20-40 psi ranges depending on specific chonker on the bike, road bikes are more in the 70-120 range. MTB tyres are like 2″ thick in all directions, road bike ones about ½”.
The combo doesn’t work that well, at 100 psi air **will** find a way to leak, and due to the much lower volume, any lost air will have more of an impact. If you blew your car tyres up to 100 psi (**DON’T**, thought r/justrolledintotheshop has had those examples), and the tyres didn’t fail catastrophically, odds are they’d be down to 80 in a day due to air escaping.
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