On what principle does the tubeless tyre work?

The discovery of the wheel to aid human work is most ingenious. However, the details of the wheel design have undergone tremendous improvements from the earlier solid wooden wheels to `mummified' wheels to the modern pneumatic wheels. Even the pneumatic wheels have evolved over time; the conventional wheel consists of a steel drum fitted with a rubber tube enclosed in a tyre made up of several plies of rubber with strengthening reinforcement materials like nylon and steel. The tube is a hollow toroidal rubber enclosure filled with air to cushion the load of the vehicle riding on the wheel. Air is filled into it through a self-sealing nozzle. During its prolonged usage the air gets slowly released by way of permeation through the tube in addition to leakage of the valve of the nozzle; in such cases it is refilled to the required pressure. The innermost lining of the tyre in a conventional tyre is of smooth rubber and is designed to reduce friction between the tube and the tyre during running. 

The main difference between the tube type tyre and the tubeless tire is that the tubeless tire is itself the tube. The plies of the tyre are similar, i.e. cross ply or radial ply depending on the type of tyre. But the inner lining layer is made up of halogen-butyl rubber like chlorobutyl rubber or bromobutyl rubber. Even in the case of an accidental puncture by a nail, the tyre improves air retention by inhibiting air permeation. The nail acts as a plug and an enthalo-butyl rubber tyre has a slow leak rather than a sudden deflation. The absence of internal tube-tyre structure, eliminates friction due to rubbing between the tube and the tyre; so it runs cooler compared to the tube type tire. Another major design difference arises from the consideration of the stability of the tyre in the rim of the wheel drum.The conventional tyres have a rigid bead heel and in a tubeless tyre the bead heal is provided with an extra wrapping that ensures better and tight fitting to the rim. This gives better cornering ability to the tubeless tyre. A tubeless tire is lighter and so creates less vibration. The sidewall of the tubeless tyre is suppler as there is no internal structure as in the case of the tube type tires and this lowers the rolling resistance during running. These factors lead to smoother ride and fuel saving.

Source: thehindu.com