A mechanical seal assembly adapted for arrangement around a rotating shaft, the mechanical seal assembly having a first and a second seal ring, the first seal ring axially shiftable relative to the rotating shaft and the second seal ring axially-fixed relative to the rotating shaft, the mechanical seal assembly comprising: an annular sleeve flange connectable to the rotating shaft, the axially fixed second seal ring connected to the annular sleeve flange and having an axially fixed seal face, the axially fixed second seal ring and the axially fixed seal face constructed and arranged to rotate with the rotating shaft; a gland plate; a stub sleeve operably coupled to the gland plate by a carrier, the axially shiftable first seal ring axially shiftable relative to the stub sleeve and gland plate in response to axial movement of the rotating shaft annular sleeve flange and axially fixed second seal ring, the axially shiftable first seal ring having an axially shiftable seal face that interfaces with the axially fixed seal face; a biasing mechanism that urges the axially shiftable first seal ring toward the axially fixed second seal ring; an annular flexible sealing membrane comprising a flange portion arrangable between the axially shiftable first seal ring and the biasing mechanism, the flange portion being axially shiftable in movement with the axially shiftable first seal ring relative to the rotating shaft by forces transmitted to the flange portion by the biasing mechanism and the axially shiftable first seal ring; a flexible connecting portion positioned at a radially inward extent of the flange portion; a coaxial portion extending axially from the flexible connecting portion, the coaxial portion held axially fixed relative to the stub sleeve by an annular band at an outer diameter and the stub sleeve at an inner diameter, the coaxial portion within a balance diameter of the mechanical seal assembly; wherein the flexible connecting portion flexes in response to axial movement of the axially shiftable first seal ring and the flange portion such that the closing force applied to the axially shiftable first seal ring is not affected; wherein axially inward translation of the shaft causes the flange portion to translate axially inboard and radially inward against the stub sleeve. an annular sleeve flange connectable to the rotating shaft, the axially fixed second seal ring connected to the annular sleeve flange and having an axially fixed seal face, the axially fixed second seal ring and the axially fixed seal face constructed and arranged to rotate with the rotating shaft; a gland plate; a stub sleeve operably coupled to the gland plate by a carrier, the axially shiftable first seal ring axially shiftable relative to the stub sleeve and gland plate in response to axial movement of the rotating shaft annular sleeve flange and axially fixed second seal ring, the axially shiftable first seal ring having an axially shiftable seal face that interfaces with the axially fixed seal face; a biasing mechanism that urges the axially shiftable first seal ring toward the axially fixed second seal ring; an annular flexible sealing membrane comprising a flange portion arrangable between the axially shiftable first seal ring and the biasing mechanism, the flange portion being axially shiftable in movement with the axially shiftable first seal ring relative to the rotating shaft by forces transmitted to the flange portion by the biasing mechanism and the axially shiftable first seal ring; a flexible connecting portion positioned at a radially inward extent of the flange portion; a coaxial portion extending axially from the flexible connecting portion, the coaxial portion held axially fixed relative to the stub sleeve by an annular band at an outer diameter and the stub sleeve at an inner diameter, the coaxial portion within a balance diameter of the mechanical seal assembly; wherein the flexible connecting portion flexes in response to axial movement of the axially shiftable first seal ring and the flange portion such that the closing force applied to the axially shiftable first seal ring is not affected; wherein axially inward translation of the shaft causes the flange portion to translate axially inboard and radially inward against the stub sleeve.