McPherson front suspension

The McPherson front suspension system uses a Sub-Frame to support the suspension components via the Lower Control Arms. Typically the frame comprises of attachment points to the body as well as steering rack, anti roll bar, exhaust and engine mount brackets.


The frame provides torsion rigidity to the body and is fabricated from stamped and welded parts.

GTO was asked to verify and propose design changes that would be necessary to meet the internal requirements of a major Automotive OEM.

The acceptance criteria were:

Component Durability/RLD Fatigue: The frame and anti roll bar (ARB) brackets must show a life greater than 10 cycles of the OEM's proving ground events. The steering rack brackets must show a life greater than 7,200 sinusoidal cycles of +/- 8kN at 1Hz applied in the lateral (Y) direction.

Lateral Stiffness check: This is primarily used as a direction indicator by making A-B comparisons.

Jacking Abuse: The permanent set of kinematic hard points shall be less than 0.2mm.

Buckling (Sub-frame overload): The LCA must buckle prior to the sub-frame. This is a crash requirement.

Modal stiffness: There is a stiffness requirement that is provided by NVH/Vehicle Dynamics.

GTO successfully verified and developed the design of the frame that is now in production and used in a number of the OEM's vehicles.