> I see that some sway bars are adjustable where they mount on the front
> suspension. I don't understand what the adjustment does. What does it
> accomplish
It lets you adjust roll stiffness, to get just the right amount. Too much
roll stiffness tends to make one wheel lift on uneven roads, while too
little may allow unfortunate camber changes (relative to the road) or even
let the suspension hit the stops in a hard corner. The latter reason is why
I have sway bars on my TR3A, and why I need a heavier bar with stickier
tires. The "right" amount for your car depends on a lot of factors,
including the kind of roads you drive on. In fact, some people even adjust
their bars at trackside, after trying out a setting.
Front/rear balance is important too, especially if you run an 'open'
differential. Too much stiffness at the drive end can lift one tire in hard
corners, leading to wheelspin and lack of acceleration coming out of the
corner. I backed off my rear bar between heats at the 2000 VTR autocross,
and shaved over a second off my time.
> and how does it do it -- the mechanics of it?
The bar is arranged such that for the car to roll against the suspension,
the bar has to twist. Generally, the adjustment sets either how much the
bar twists for a given amount of body roll, or the force required to twist
the bar (or both).
For example, shortening the arms while keeping the same attachment points to
the suspension will reduce the lever arm, which both means the bar has to
twist farther for a given suspension movement, and it takes more force (at
the end of the arms) to twist the bar a given amount.
Since the bar's mounting and end link bushings also deform as the car rolls,
changing them can make a smaller difference. I've even seen spring-loaded
end links, where you can change the springs to adjust roll stiffness.
Randall
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