Originally Posted by 130R
The sway bar isn't a lever, and doesn't gain mechanical advantage by being longer, in fact, because the stiffness of a sway bar is proportional to its length, they lose stiffness, or become less efficient the longer they are.
The stiffness of a sway bar is also proportional to the 4th power of the diameter, so it's no coincidence that the FE4 rear bars have a larger diameter than the FE3 rear bars.
Sway bars do utilize lever arms at the ends, but once again, these are proportional to their length, which is why the closest hole to the bar is the stiffest setting, and the further out you go, the less efficient they are.
The FE3 bars also appear to have shorter lever arms (more efficient) than the FE4 bars.
So why do people keep posting the FE4 bars are more efficient? Is this just an assumption that bigger/longer is better? Or is there something I'm missing?
People post whatever they read on the internet (not targeted towards anyone). What you are referring to is stiffness at the end link and you are right. But you also have to consider FE3 bar mount inboard of damper/spring assembly with motion ratio about 0.4:1 and FE4 bar mount outboard of damper/spring assembly with motion ratio about 0.8:1 (my guess base on 0.7:1 damper/spring assembly motion ratio). Motion ratio has to be square to get the wheel rate so given the same strength bar, FE4 mounting point will be 4x stronger at the wheel.