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Discussion Starter #1
What is the difference between having a sway bar that is straight across, as apposed to conforming to the chassis/floor contours? Does a certain design work better, or is it more a matter of space?
 

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The design/shape, and especially the diameter/weight/hollow or solid characteristics of the sway bar are such in order to affect (or rather prevent) rolling when the car is cornering. The application characteristics are different depending on how the car is used - that's why you will find race cars with large bars (and stiff suspensions), which is not typically how you would set-up a street car. Yes, the contours of the car do need to be taken into consideration, but this is not the basis for the design. It would be helpful if you mentioned which car you are taking about and specifically which bar designs you have questions about...

Best regards,
 

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The curves in some bars are only there for packaging reasons. The effective rate of the bar is dependent on the overall diameter of the bar, the wall thickness (if it is hollow), the length of the portion of the bar that is twisted by suspension movement, and the length of the lever arms (i.e. the part that is not twisted. Of course the effective rate will also be changed if you mount the bar to the a-arm at a position closer to or more distant from the inner pivot.

Erik
 

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Discussion Starter #5
The curves in some bars are only there for packaging reasons. The effective rate of the bar is dependent on the overall diameter of the bar, the wall thickness (if it is hollow), the length of the portion of the bar that is twisted by suspension movement, and the length of the lever arms (i.e. the part that is not twisted. Of course the effective rate will also be changed if you mount the bar to the a-arm at a position closer to or more distant from the inner pivot.

Erik
The inner pivot being the mounts, or at the end links?
 

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Discussion Starter #6
The applications are an '85 535i, and '84 GTV6
 

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As in the distance between the green dots on the attached. (distance X)

Moving the ARB closer/further away from the control arm pivot changes the leverage.
 

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Discussion Starter #9
Okay that makes sense. Is there any way I could move the mount position or weld extra metal onto the bar to experiment with different stiffnesses. Also what is the purpose of adjustable end links, and what do they mean by preload on the sway bar? Well, I guess I know what it means but what purpose does it serve? Thanks.
 

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Adjustable end links allow you to set the sway bar up with no preload, or with a predefined amount of preload. Preload mean that you have adjusted the end links to cause some "twist" in the bar when the car is at normal ride height. Essentially, this changes the amount of weight each corner of the chassis carries. If you race on tracks that have more rights than lefts, for example, and if your car has a push in right handers, you might band aid things by preloading some weight into the right front. The car will push less in right-handers. Of course the downside is that it will push more in left-handers. Depending on the track you may not care. For a street car, just set things up square.

Erik
 

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Is this for the GTV-6? There are plenty of cheap bars out there. You can also modify your sway bar by welding in a longer arm and drilling holes to make it adjustable. This would be better done on an aftermarket shankle style bar than OEM. Shankle bar has a flat blade you could drill holes into to begin with. The different holes would change the effective rate of the bar.
 

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Erik,

I have adjustalbe end links. My car understeers on right turns, but oversteers on left turns. I don't have corner scales available to me. What should I do on the sway bars to help get rid of my handling problem? Should I focus more on preload on the front or the rear of the car first?
 

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Grant, I hope I didn't set myself up as an expert on this topic:)! What I have done on my race car is first properly scale the car to get the cross weights correct. Of course, to do this, you have to have some form of adjustable spring perches. On a 105, you can just shim under the springs or pans on the front. Not sure how you'd do that on a transaxle car. If you do scale the car, make sure you have the driver's weight in the seat when you do it. I weigh 260 and it makes a huge difference!

As for preload, I then measure the change in corner weights for each 2 turns or so of the end links on the front or rear. That way, I know how much preload I'm getting, and I can always go back to the balanced state. My car has always pushed more in right-handers also. I've always attributed it to my weight on the left side of the car. I have tried running a little preload on the right front and it seems to help. But don't forget, there is always a trade-off when turning the other way. I don't know how your end links mount, so I can't say whether you need to lengthen or shorten your links. But just visualize the twist in the bar "pushing down" on the right front and "pulling up" on the left front.

Again, the first thing I would do is borrow some scales and figure out what your baseline is! Hope that helps.

Erik


Erik, I have adjustalbe end links. My car understeers on right turns, but oversteers on left turns. I don't have corner scales available to me. What should I do on the sway bars to help get rid of my handling problem? Should I focus more on preload on the front or the rear of the car first?
 

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I don't think welding metal onto a sway bar will get you what you want. The bars are essentially giant drawn wire, and welding much onto the bar will soften the metal enough that you will change its stiffness. You could end up with a softer bar by adding metal!

Robert
 
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