Automobile Engineering in ME
The rigid suspension is beneficial when

It is desired to reduce the unsprung mass
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 improve tyre to ground contact characteristics

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Automobile Engineering in ME
The compression ratio in petrol engine is kept less than in Diesel engine because

It is just customary to have less compression ratio in petrol engines
Less compression ratio gives better performance
It makes petrol engines lighter
Higher or equivalent compression ratio in petrol engines is not possible due to pre-ignition

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