BRZ/FR-S/GT86 Rear Lower Control Arm Design

There are two major problems with the OEM rear lower control arm on the BRZ/FR-S/GT86:
1. It doesn’t offer any camber adjustment
2. It is very weak under longitudinal loading


Originally, I was going to try a shim stack design for the rear lower control arm.  However, I was unsatisfied with the design because it would either be too heavy or too soft.  So, I went back to the drawing board and started from scratch.  This time I went with a threaded rod adjustment rather than shim stacks because the shims were adding too much mass.  This is the design:


With a threaded rod design, we were able to reduce the mass of the arm while increasing stiffness. Here you can see the stress plot side-by-side.  The OEM arm:

OEM Stress

Note how twisted the arm becomes where the arm tapers.  Under extreme loading, the arm is likely to break at the welds.  Our arm:

LCA V4 Stress

Our FEA results show that stress is reduced in the arm by 900%, and stiffness is increased by 1100% while maintaining the same mass.


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