Method for optimizing a rear suspension of a vehicle of ambulance type or transport for persons with reduced mobility type, the suspension comprising: - two original springs, each having an original stiffness and an original sag; - two original shock absorbers, each having: an original expansion force at low speed, for a deflection speed of the original shock absorber that is less than 0.1 m.s -1 , an original compressive force at low speed, for a deflection speed of the original shock absorber that is less than 0.1 m.s -1 , characterized by the method having the following steps: a) replacing the two original springs with two dedicated springs , each having a stiffness strictly less than the original stiffness and a sag (F) strictly greater than the original sag; b) replacing the two original shock absorbers with two dedicated shock absorbers , each having: - an expansion force at low speed, for a deflection speed of the dedicated shock absorber that is less than 0.1 m.s -1 , strictly less than the original expansion force at low speed; - a compressive force at low speed, for a deflection speed of the dedicated shock absorber that is less than 0.1 m.s -1 , strictly greater than the original compressive force at low speed. - two original springs, each having an original stiffness and an original sag; - two original shock absorbers, each having: an original expansion force at low speed, for a deflection speed of the original shock absorber that is less than 0.1 m.s -1 , an original compressive force at low speed, for a deflection speed of the original shock absorber that is less than 0.1 m.s -1 , characterized by the method having the following steps: a) replacing the two original springs with two dedicated springs , each having a stiffness strictly less than the original stiffness and a sag (F) strictly greater than the original sag; b) replacing the two original shock absorbers with two dedicated shock absorbers , each having: an original expansion force at low speed, for a deflection speed of the original shock absorber that is less than 0.1 m.s -1 , an original compressive force at low speed, for a deflection speed of the original shock absorber that is less than 0.1 m.s -1 , characterized by the method having the following steps: a) replacing the two original springs with two dedicated springs , each having a stiffness strictly less than the original stiffness and a sag (F) strictly greater than the original sag; b) replacing the two original shock absorbers with two dedicated shock absorbers , each having: a) replacing the two original springs with two dedicated springs , each having a stiffness strictly less than the original stiffness and a sag (F) strictly greater than the original sag; b) replacing the two original shock absorbers with two dedicated shock absorbers , each having: - an expansion force at low speed, for a deflection speed of the dedicated shock absorber that is less than 0.1 m.s -1 , strictly less than the original expansion force at low speed; - a compressive force at low speed, for a deflection speed of the dedicated shock absorber that is less than 0.1 m.s -1 , strictly greater than the original compressive force at low speed. <EOS>