canadian said:
i can understand the concept behind lighter wheels (static weight vs. rotational weight... or is it mass?), but i don't follow when it comes to sway bar mounting points. is it because the axle travels up and down vs the frame being static? and can the difference be *that* dramatic?
Unsprung weight is anything that is BELOW the springs, wheels have an effect on this, as do other things such as axle size, tire size etc.
When you increase UNSPRUNG weight it has a larger effect on the ride quality of the vehicle. If you add additional weight to the axle its going to have more UPWARD motion when hitting a hole and rebounding from that hole. When it comes upward its going to UPSET the vehicle more. Do a search for UNSPRUNG WEIGHT and possibly its posted somewhere or there is an article somewhere that explains it better to you than I have. I know its a bad thing and I understand WHY its bad I just cant explain it to you.
Unsprung weight is one of the reasons that most performance cars are NOT solid axle cars, IRS suspended cars not only handle better but they are also less prone to being upset because of the less unsprung weight. Notice the C5's, the Cobra's etc are IRS cars.
In your post you refer to ROTATIONAL MASS, I agree that also has an effect on performance and handling but its not the same as unsprung weight. The concept is completely different.
Since the weight of the ST bar (and all its mounting hardware) is being supported by the axle assembly its adding to the UNSPRUNG WEIGHT of the axle assy. Where as the ADDCO Bar is supported by the frame rails of the vehicle its considered 'SPRUNG WEIGHT' basically anything thats ABOVE the springs.. Make sense ?? Prolly not coz I did such a crappy job 'splaining it.
Sorry man, maybe someone else could chime in and explain it better.