I am an old autocrosser and understand that too much sway bar can overpower the springs and actually lift an inside wheel to the point of losing traction. Although I don't think any of the GM bars can do that. It has to do with how a sway bar works, weight transfer cause the outside wheel to push up toward the body, the sway bar transfers that lift to the opposite wheel, etc.
The problem with rating by diameter is hollow bars besides being lighter, are usually stiffer than solid bars. It's hard to compare hollow bars, because wall thickness on a hollow bar of the same diameter can have a huge difference in spring rate. There are formulas for calculating spring rate from the physical dimension, but I rather not research them unless I have to. I was hoping someone knew the values.
Here is what I did:
I essentially had the bars mounted to my shop bench, had one bar end on the scale while I pushed on the other end, deflecting it in quarter inch increments and reading the scale. So when I was using my bathroom scale, I was measuring force applied to the scale by my deflecting the other end of the bar. This gives a spring rate curve that should be linear. One problem is I'm using one spring (the scale) to measure the force exerted by another spring (the bar). Plus the scale will compress alittle so the deflection readings are going to be alittle off. I thought that would be a minor error, but I'm not sure if there are other problems with measuring with this method.
Another way to figure out the spring rate is mount the bar, fix one end from moving and hang known weights on the end of the bar and measure how much moves it an inch. That would give the lbs/in spring rate. I'll try that and see if I get the same results.
Thanks,
Carmen