AKG Motorsport Rear Subframe Bushings, Poly 75D – E46, Z4Product Description These BMW E46, Z4 Polyurethane (75D) Rear Subframe Bushings virtually eliminate subframe movement for effective power transfer through the rear end. Rear subframe bushings are also the first step in maintaining proper rear end geometry and alignment. The stock rubber subframe bushings deflect as torque moves through the drivetrain, allowing the entire subframe to move. Virtually eliminate rear subframe movement and start dialing in