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

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
Compression ring and aids the top ring in sealing and cooling
Cushion ring which prevents piston slap and knock

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Automobile Engineering in ME
The rigid suspension is beneficial when

Large changes in load make it necessary to have a large suspension stroke
It is desired to have more flexibility in design
It is desired to reduce the unsprung mass
It is desired to improve tyre to ground contact characteristics

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