How does this suspension work?

[anamgee]

I recently purchased a Mercedes ML350 (W164) and as usual I started to see how to tweak the handling and was very surprised with what I saw. Attached are pictures of the Sway bar and the bushing used to connect the sway bar to the body. How would this sway bar work? In all my other vehicles, the sway bar would be able to swing freely in the bushings, but in this case the bushing is clamped to the sway bar, and then the bushing is clamped to the body. How does this even work?

 

[Nereth1]

Ok, I clearly misunderstood, apologies all.

How can you leave the stock springs and preload the sway bar without changing your ride height? Unless (which I suspect to be the case) the stiffness of the rubber bushings is basically negligible in which case you haven't really made any meaningful change?

 

[anamgee]

The change is meaningful. If you read my post dated 23rd Oct, I mentioned this

One of the test I did was to loosen the bar and tighten it when the vehicle is on the ground, and it drove horrible because the soft springs on their own are not capable of carrying the weight of the vehicle. The optimum setting I discovered was raising the vehicle by 2 inches and then tightening the sway bar and bushings. When I dropped the vehicle back to the ground, the ride height was still the same, but the sway bar was now preloaded and contributing as a spring.

 

[TC3000]

Now, I may see this wrong, but from what I gather, you may have a "secondary" effect at play here.
I don't think, that you actually "preload" your anti roll / sway bar with what you do, but you may get a effect, which feels like "having a bigger bar", and from your comments, there seems to be a perceivable change in handling, so something is "going on".

My 2 cents, is that is that by "preloading" the rubber bushings, you end up with a much "stiffer" bushing in radial direction.
This in turn could mean, that your anti roll /sway bar now actually has to "twist" and work as a it is intented to work.
If you tigthen the bolts with the car on the ground, and have little/no prelaod on the bushings, then , seeing that the bar seems to be quite "stiff" it may becomes easier for the whole assembly to move up and down in the rubber bushings, then to actually "twist" the ARB/sway bar in roll (during cornering).
To understand/picture better what I mean, consider what would happen if you take one of the mountigs of the ARB completely off.
The ARB wouldn't twist the free and would just move up (or down), the ARB trying to stay parallel with the road, while the body would roll.

With the "none preloaded" rubber bushings, you could get a similar effect, the whole assembly will follow " the path of least resistance".
The ARB would first "tilt" in relation to the body, trying to stay parallel with the road and avoiding to be twisted (work like a ARB), if the deflection in the rubber bushings come to an end, the bar will start to twist (work like a ARB).
Now by "preloading" the bushings, the bar cannot longer (or much less) "tilt", and will start twisting sooner/more, providing a larger force to oppose the roll moment (reducing the roll angle), and doing so much sooner, what you may feel like a "sharper" handling.
The "extreme" case, to take this further, would be to replace the rubber mounts by nylon bushings, in this case, you would "force" the ARB to twist right from the beginning --> no secondary/parasitic "tilting" movement w.r.t. the body.

Now, I dunno what MB "intented" to be the "correct" setup,but I would agree with what Brian said.
If the system isn't "designed" to work like this, you may "overstress" your bushings in shear, and will limit their life span.
At one point you may get a "shear failure", the bushing cracking/rupture between the inner and outer clamp/ring and reducing the preloed/stress after a while.
This would be especially the case, if you use your car "off road", and make use of all the suspension travel on a regular basis.

 

[GregLocock]

The alignment charts for the vehicle should specify the nominal ride height.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[anamgee]

Correct, but the service manual is not available to customers.