Question : I NEED your advice on the changing of a car's suspension.
I was advised that I need not change the suspension at the rear but only
the front. Is this correct ?
How about cars which are over 10 years old ? Don't you think it is wise to change the suspension at the rear as well ?
Anyway, why must we change the suspension if the car is only for city use where the road is good and smooth ?
I think you are talking about the shock absorbers rather than the whole suspension set-up.
If that is the case, then you can change either the front or the rear but the shock absorbers should be replaced only in pairs and preferably of the same specifications as the old ones.
If you wish to upgrade the shocks, then all four should be replaced so
that the front and rear pairs match.
If you have no problems with the shocks such as uneven wearing of the tyres or suspension bottoming, then really there is no reason to change them.