An end member assembly dimensioned to receivingly engage an associated end of an associated flexible spring member, said end member assembly having a longitudinal axis and comprising: a first end member section including a first section wall extending radially outward to an outer peripheral edge; a second end member section including a second section wall that has an outer surface dimensioned such that the associated flexible spring member can form a rolling lobe therealong, said second end member secured to said first end member such that an end member chamber (252, 252A, 252B) is defined therebetween; an end member partition section disposed between said first and second end member sections (250, 248), said end member partition section including an inner peripheral edge disposed along said first section wall of said first end member section and an outer peripheral edge disposed along said second section wall of said second end member section such that said end member chamber (252, 252A, 252B) is separated into at least a first chamber portion disposed toward said first end member section and a second chamber portion disposed toward said second end member section with a passage extending through said end member partition; and, a control device disposed in fluid communication along said passage in said end member partition section, said control device operative between: a first condition in which said first and second end member chambers (252A, 252B) are fluidically isolated from one another through said passage under differential pressure conditions at or below a predetermined pressure threshold; and, a second condition in which said first and second end member chambers (252A, 252B) are disposed in fluid communication with one another through said passage under differential pressure conditions exceeding said predetermined pressure threshold. a first end member section including a first section wall extending radially outward to an outer peripheral edge; a second end member section including a second section wall that has an outer surface dimensioned such that the associated flexible spring member can form a rolling lobe therealong, said second end member secured to said first end member such that an end member chamber (252, 252A, 252B) is defined therebetween; an end member partition section disposed between said first and second end member sections (250, 248), said end member partition section including an inner peripheral edge disposed along said first section wall of said first end member section and an outer peripheral edge disposed along said second section wall of said second end member section such that said end member chamber (252, 252A, 252B) is separated into at least a first chamber portion disposed toward said first end member section and a second chamber portion disposed toward said second end member section with a passage extending through said end member partition; and, a control device disposed in fluid communication along said passage in said end member partition section, said control device operative between: a first condition in which said first and second end member chambers (252A, 252B) are fluidically isolated from one another through said passage under differential pressure conditions at or below a predetermined pressure threshold; and, a second condition in which said first and second end member chambers (252A, 252B) are disposed in fluid communication with one another through said passage under differential pressure conditions exceeding said predetermined pressure threshold. a first condition in which said first and second end member chambers (252A, 252B) are fluidically isolated from one another through said passage under differential pressure conditions at or below a predetermined pressure threshold; and, a second condition in which said first and second end member chambers (252A, 252B) are disposed in fluid communication with one another through said passage under differential pressure conditions exceeding said predetermined pressure threshold.