Purpose of an aftermarket Rear Sway Bar?

[damronjr]

I am starting this thread in conjunction with the question asked on this page http://forums.genvibe.com/zero...age=2 so it will be easy to find for others later and hopefully this will be seen easier. I recently installed a Progress RSB only because I had already paid for it and figured I may as well use it. The reason I say this is I just don't see the point or difference between this bar (or any other for that matter) and the stock bar that was in there. The stock bar is a solid piece of steel bar the fits inside the steel casing that runs across the rear suspension. Personally I don't even see the point of the stock RSB with that non-moving / flexing casing there. Then to go and spend $100 on an aftermarket bar that is a hollow tube with 2 hollow tube posts welded to it by 2 plates just doesn't make any sense. It fits in the same place as the old bar, you don't adjust anything, as nothing is adjustable or even moveable. Sure, it may look nicer, but with my 2" drop I don't think anyone is going to see it anyways! Sure, it's thicker, but it's hollow! And the construction and integrity of the A/M bar seem much weaker. I just don't see how this or any other bar provides any stability in the handling and I am thinking I just wasted $100. I am hoping someone knows something I don't or I am missing something here.

[SCVibe]

The bar is supposed to keep the suspension planted during cornering, and making it hollow lightens the weight as long as the material it is made out of is rigid. Also check this out:http://auto.howstuffworks.com/question432.htm

[damronjr]

Quote, originally posted by SCVibe »The bar is supposed to keep the suspension planted during cornering, and making it hollow lightens the weight as long as the material it is made out of is rigid. Also check this out:http://auto.howstuffworks.com/question432.htmWell, after looking at this and Progress' website, my understanding of HOW these things are supposed to work was reinforced, but what I don't understand is how this makes a difference in OUR Vibes. It seems that this bar would be exactly the same as the OEM bar. How is it different and what does it change?

[Raven]

The Progress bar is slightly larger in diameter than stock. A very small increase in diameter translates into a huge % increase in stiffness. MadBill would know the exact numbers. When cornering the outside suspension is compressed because of centifugal force, pushing the wheel up. This makes the body roll to the outside of a corner. A stiffer bar resists the force and thus reduces the body roll. This is a simple explanation, but I hope it makes sence. You did not waste your money, stiffer roll bars make a huge difference in handling. I know my Progress bar did.

[cieglo]

Quote, originally posted by Sunny »The Progress bar is slightly larger in diameter than stock. A very small increase in diameter translates into a huge % increase in stiffness. I don't do this type of engineering much anymore...but let's see what I can remember: Stiffness of a beam - which the RSB basically is, is related to the moment of inertia (I). I for round members is calculated using the diameter to the 4th power. For hollow members, subtract the hollow diameter (also to the 4th power) from the outer D^4. The actual formula is hard to type out: (pi/64)*(D^4-d^4)I don't know what your tube diameters are, but here a rough example:If the stock RSB is a solid 0.875" round bar the I would be 0.029in^4For a hollow tube 1" diameter with .125"wall the I would be 0.033in^4This is something like a 13% increase in I with a 13% increase in diameter with only about 65% of the weight (based on cross-sectional area).I'm sure the actual calculations are pretty complex, but they have to come back to the I of the RSB.

[kharman]

does the progress sway bar made for the matrix fit the vibe?....

[damronjr]

Quote, originally posted by kharman »does the progress sway bar made for the matrix fit the vibe?....I would assume but am not positive. I think the one I bought on Ebay said it was for the Matrix/Vibe/Corolla. Not + though.