Automobile Engineering in ME
The function of a second ring is that it is a

Compression ring and aids the top ring in sealing and cooling
Back up oil control ring which will work in place of the bottom ring when it is broken
Back up compression ring which will work in place of the top ring when it is broken
Cushion ring which prevents piston slap and knock

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

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

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