What is Front View Swing Arm (FVSA)?
The front view swing arm (FVSA) instant centre location controls the roll centre height, the camber change rate and the tyre lateral scrub. The instant centre can be located inboard of the wheel or outboard of the wheel. It can be above ground level or below ground level. The FVSA is a theoretical arm mounted at the knuckle in the wheel centre, pivoting about the instant centre.
The FVSA moves in an arc when the wheel is moved vertically up and down. This arc produces camber gain in the system. The longer the FVSA, the less camber gain a system has. Therefore, the FVSA is a key area of suspension geometry when trying to fine tune camber gain in a system.
The diagram below shows how two short links can be replaced by one longer link. This long link is the front view swing arm.
Rate Of Change Of The FVSA
Instant centres move with wheel travel; how fast they move is a function of the absolute and relative lengths of the control arms in the front and side views. A camber curve can be made to have more or less camber change with wheel travel by altering the length of the upper control arm even though it is aimed at the same instant centre at ride height. What this does is keep the same swing arm length at ride height but it shortens or lengthens faster or slower with wheel travel.