A sliding door assembly for a motor vehicle comprising: a vehicle door; a guide rail; a self-adaptive carriage mated with the guide rail over a length of travel and including a biasing member (82, 84, 88, 182) that permits the self-adaptive carriage to flex at any given position along the length of travel, the self-adaptive carriage further includes a body that surrounds at least a portion of the guide rail, and a roller assembly (34, 134, 251, 257) including a roller bracket (46, 58, 68, 146, 158, 168, 255) connected to the carriage body and a roller (44a-c, 144d, 144e, 244i, 244j, 244L) carried by the roller bracket (46, 58, 68, 146, 158, 168, 255) for rotation about an axis, and wherein flexing of the self-adaptive carriage moves the axis of rotation of the roller (44a-c, 144d, 144e, 244i, 244j, 244L) relative to at least a portion of the carriage body and wherein the biasing member (82, 84, 88, 182) acts on the roller bracket (46, 58, 68, 146, 158, 168, 255) to permit movement of the roller (44a-c, 144d, 144e, 244i, 244j, 244L) relative to the body of the carriage and wherein the biasing member (82, 84, 88, 182) is a compressible member situated at least partially between the body of the carriage and the roller bracket (46, 58, 68, 146, 158, 168, 255) of the roller assembly (34, 134, 251, 257) to permit movement of the roller relative to the body of the carriage; and a bearing arm pivotably connected to the self-adaptable carriage and configured for attachment to a vehicle body, characterized in that the guide rail is attached to the vehicle door and includes two rolling surfaces (24a-c, 224b, 224c, 241, 249) oriented at different angles and the carriage includes a pair of rollers (44a-c, 144d, 144e, 244i, 244L) each adapted to engage one of the rolling surfaces (24a-c, 224b, 224c, 241, 249), each roller (44a-c, 144d, 144e, 244i, 244j, 244L) being yieldably biased into engagement with its respective rolling surface (24a-c, 224b, 224c, 241, 249). a vehicle door; a guide rail; a self-adaptive carriage mated with the guide rail over a length of travel and including a biasing member (82, 84, 88, 182) that permits the self-adaptive carriage to flex at any given position along the length of travel, the self-adaptive carriage further includes a body that surrounds at least a portion of the guide rail, and a roller assembly (34, 134, 251, 257) including a roller bracket (46, 58, 68, 146, 158, 168, 255) connected to the carriage body and a roller (44a-c, 144d, 144e, 244i, 244j, 244L) carried by the roller bracket (46, 58, 68, 146, 158, 168, 255) for rotation about an axis, and wherein flexing of the self-adaptive carriage moves the axis of rotation of the roller (44a-c, 144d, 144e, 244i, 244j, 244L) relative to at least a portion of the carriage body and wherein the biasing member (82, 84, 88, 182) acts on the roller bracket (46, 58, 68, 146, 158, 168, 255) to permit movement of the roller (44a-c, 144d, 144e, 244i, 244j, 244L) relative to the body of the carriage and wherein the biasing member (82, 84, 88, 182) is a compressible member situated at least partially between the body of the carriage and the roller bracket (46, 58, 68, 146, 158, 168, 255) of the roller assembly (34, 134, 251, 257) to permit movement of the roller relative to the body of the carriage; and a bearing arm pivotably connected to the self-adaptable carriage and configured for attachment to a vehicle body, characterized in that the guide rail is attached to the vehicle door and includes two rolling surfaces (24a-c, 224b, 224c, 241, 249) oriented at different angles and the carriage includes a pair of rollers (44a-c, 144d, 144e, 244i, 244L) each adapted to engage one of the rolling surfaces (24a-c, 224b, 224c, 241, 249), each roller (44a-c, 144d, 144e, 244i, 244j, 244L) being yieldably biased into engagement with its respective rolling surface (24a-c, 224b, 224c, 241, 249).