Torsion-Beam Suspension
Torsion-beam suspension is a rear layout in which two trailing arms are joined by a cross member that twists as the wheels move differently.
Semi-independent behavior
When both wheels rise or fall together, the beam moves largely as one assembly. When one wheel moves relative to the other, the cross member twists and contributes roll stiffness. The wheels are therefore coupled, but not as rigidly as with a solid axle.
The beam can combine compact packaging, low mass, and relatively few joints. Its geometry and compliance offer less independent tuning freedom than a complex multi-link axle, and the term does not state the spring, damper, bushing, or toe-control details.
For the distinction between independent, semi-independent, and rigid layouts, see Suspension Construction. For wheel-path and alignment behavior, see Suspension Kinematics and Vehicle Dynamics.