Death Wobble - Possible Resolution - Page 9

E350 · 04-14-2015, 09:48 AM

sidetrak06: A picture is worth a thousand words to my pea brain. Got it! You are going to correct frame/suspension induced "bump steer" first. Works for me. The bargain you make on this forum by drawing out the gods carringb, mgmetalworks, Ujoint and Bajasportsmobile, is that you have to keep contributing to (at least your thread) so as to not leave us hanging. Because we are now invested in your outcome. Good, luck and keep posting.

Now, how do you make do those drawings?

sidetrak06 · 04-14-2015, 09:56 AM

Quote:

Originally Posted by E350

sidetrak06: A picture is worth a thousand words to my pea brain. Got it! You are going to correct frame/suspension induced "bump steer" first. Works for me. The bargain you make on this forum by drawing out the gods carringb, mgmetalworks, Ujoint and Bajasportsmobile, is that you have to keep contributing to (at least your thread) so as to not leave us hanging. Because we are now invested in your outcome. Good, luck and keep posting.

Now, how do you make do those drawings?

I definitely plan on keeping everyone up to date on my progress. Right now, I am waiting to hear back from Boulder Offroad so I can see what bushings are available for my radius arms as well as discuss why they setup the radius arms to be nonparallel.

The drawings were done in a very expensive 2-D software package called Microsoft Paint.

BajaSportsmobile · 04-14-2015, 11:47 AM

Test the radius arm bushings by restricting their movement on a test run - thus the idea of using a strap or whatever you are comfortable using. Wedge something in there... just a test. No brainer.

sidetrak06 · 04-14-2015, 12:57 PM

Quote:

Originally Posted by BajaSportsmobile

Test the radius arm bushings by restricting their movement on a test run - thus the idea of using a strap or whatever you are comfortable using. Wedge something in there... just a test. No brainer.

I will give this a try. You are right, it is a no brainer. I just need to pick up some serious straps!

UJOINT · 04-14-2015, 02:15 PM

I say try it too, Can't hurt as you're just trying to isolate the issue.

I'll spill my can of worms here too.... Have a guaranteed DW solution! Our suspension! Eliminates it every time

sidetrak06 · 04-14-2015, 02:27 PM

Quote:

Originally Posted by UJOINT

I say try it too, Can't hurt as you're just trying to isolate the issue.

I'll spill my can of worms here too.... Have a guaranteed DW solution! Our suspension! Eliminates it every time

There is no doubt that leafs would get rid of this issue! I think I missed that train however...

carringb · 04-14-2015, 02:47 PM

Perhaps this might better explain why I think the geometry is the root cause:

sidetrak06 · 04-14-2015, 04:08 PM

Wouldn't that scenario occur in all radius arm setups if only one wheel drops? The side of the axle that drops into a pothole has to follow the arc of the radius arm. The as the axle drops, the trac-bar would pull the axle slightly towards the drivers side of the vehicle and as the axle raises it would push the axle slightly towards the passenger side. The radius arms should have total control over the fore-aft movement.

carringb · 04-14-2015, 05:05 PM

Quote:

Originally Posted by sidetrak06

Wouldn't that scenario occur in all radius arm setups if only one wheel drops?

That is correct under the condition you illustrated. That is also why the factory radius arms under the F-series (and QuadVans) are parallel to the ground. It minimizes the magnitude of fore-aft movement during up/down motion. This is also why some F-series trucks develop DW after owners install inexpensive, tall lifts which do not re-locate the radius arms to compensate for the taller springs.

So, when you combine the elevation angle of your radius arms (they appear that way in the static pics) with the steer angle introduced by horizontal motion created by the track-bar arc, you are twice as likely to encounter DW than if only one of those conditions existed. And... the magnitude of the DW will be greater with those combined affects.

sidetrak06 · 04-14-2015, 06:29 PM

Agreed, looking at the van from the side...the more parallel the radius arms are to the frame the less you will see this effect since angle changes have much less horizontal movement. My question is, when looking at the frame from above, how does having the radius arms not parallel to the frame increase this effect? Sorry to beat this issue to death, I am just trying to decided whether or not I want to change the mounts on my arms.