Automobile Engineering in ME
The main function of the tread pattern on tyre is that

The tread pattern protects the tyre's inner carcass from small stones and pieces of glass
The crests between the tread grooves absorb road noise
The tread grooves pass air between the tyre and road surface, thereby preventing tyre from overheating
In wet conditions, the tread grooves expel water that is drawn between the tyre and road surface

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Automobile Engineering in ME
It is necessary to maintain the valve clearances as they

Increase the speed at which the valves move up and down
Make the crankshaft turn smoothly
Reduce the resistance to sliding that occurs between the cam and the tappet
Allow for lengthening of the valves owing to the heat of combustion

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