Just thought i'd add this to the tech sticky. Feell free to post anything else you think is relevant.
Sway bars (also known as stabiliser bars) are used to limit and control body roll during cornering.
Have you ever driven round a corner at speed and felt the car rolling away from the apex and felt like the car was going to tip over?
This is because the body rolls as the car leans away from the centre of radius of the corner.
Swaybars aim to limit this body roll. Given that most Honda's run independant rear suspension (IRS) front and back, the focus will be on sway bars on IRS setups. Furthermore, we will focus on the rear sway bar of a car as this has the greatest impact on body roll (the same concept applies to the front sway bar).
There are three main points of contact for the sway bar. Namely the subframe, left control arm and right control arm. The most important aspect of the sway bar is that it is mounted firmly to the subframe, as these mounts will be dealing with a lot of the tortional force the swaybar receives under heavy cornering.
The subframe (the main mounting point for the swaybar) is directly bolted to the chasis of the car. The control arms (which connect the wheel hubs to the chasis) are then attached to the subframe, and the other contact points for the sway bar are located on both left and right control arms.
The picture below shows the left control arm, and how one end of the sway bar is connected to it.
http://www.ozhonda.com/tech/swaybar/left_arm.jpg
The next picture below, shows the sway bar mounted to the subframe via two mounting plates (the silver plates). This plate provide a stronger mounting position, absorbs some of the the force put on the subframe and prevents subframe tearout.
http://www.ozhonda.com/tech/swaybar/bar.jpg
During normal operation, the part of the sway bar between the mounting points remains stationary, while the 'arms' of the sway bar (the sections between the mouting point and the control arms) move up or down and always in a different direction to one another. This opposite movement in the arms apply a tortional (twisting) force on the sway bar and depending on the diameter of the sway bar, helps reduce body roll by limiting movement of the arms.
Think of it as trying to twist a long rod like object. The bigger the diameter of the object, the harder it is to twist. Sway bars effectively convert body roll to the tortional force applied to the sway bar. Hence by having a thicker diameter sway bar, you can reduce body roll by a larger amount.
Here is a link to the Whiteline website which gives a rough comparison of swaybar diameter VS the effect on body roll.
For a more detailed reading I suggest having a read of the swaybar FAQ on the Whiteline website. Another explanation can be found on the HowStuffWorks website.
