The powder they use is either chalk powder or talcum powder or some rare occasions they use boric acid powder
مهندس امیر مبشراقدم

These are used to act as lubricant between tube and tyre. As there is a lot of heat generating through friction between road and tyre, this heat is captured in the tyre and is conducted to the tube. If powder is not used there are chances of tubes and tyres getting stuck to each other due to immense heat.

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