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On 28 Aug 2004 at 23:16, Steven Ayres wrote: > GregM=> did you mean *any* Type III, or just a lowered one? > > Jim's right that lowering lessens the effect of the anti-sway bar, to the > extent that there is less suspension travel. But as long as the suspension > is traveling, anti-sway is working. It's not just the lack of travel. It's more that a stiffer suspension overall is less improved by adding an anti- sway bar. For example, if our suspension was rigid, a sway bar would do nothing other than just add weight. When you lower our cars by moving a notch or 3 on the torsion bars, the angle of the trailing arms changes with respect to vertical. One effect of this, which I had not realized until a recent list conversation, is that the effective spring rate (the inverse of the suspension compliance) goes up because it is a function of the cosine of this angle. As this angle decreases (it starts at ~90 degrees) that cosine changes from 1 to something less than 1 and the spring rate, in lb/in, changes as 1/cosine (angle). So the suspension gets stiffer just by virtue of this suspension change, without actually changing the springs (torsion bars) themselves. One way to visualize this is to think of how the suspension works when the trailing arms are in the stock ~horizontal position: They are free to let the wheel move up and down with respect to the body of the car. But imagine what you would get IF you could do the extreme lowering of rotating the trailing arms 90 degrees, so they were vertical. At this point the suspension would be completely rigid; no amount of downward force on the body would make the body sink at all on the wheels. The only compliance left in the suspension would be in the tires themselves. In between vertical and horizontal trailing arms the situation is in between the stock and infinite spring rates, and you can calculate the change as 1/cos (angle). What I've described above is what I call the effect on the static spring rate. This is simply what you notice when pushing down on the front of a parked car. The dynamic spring rate is slightly different, because the tire pressure center moves forward on the tire contact patch depending on the speed. I suspect this effect is small, but it becomes more important as the angle decreases (ie, as the car is lowered.) A more important dynamic effect is from "bumps" in the road. When the tire encounters bumps, these produce forces which are radial thru the center of the tire, but they originate in front of the normal tire contact patch. The angle they make depends on the height and shape of the bump, but it always decreases the effective angle making 1/cos (angle) larger, which makes the suspension stiffer against bumps. Again, this effect becomes more pronounced as the car is lowered and the static angle is decreased. -- ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ Shameless link for search engines: http://listarchive.type3.org ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~