Thread: restricted articulation

Originally Posted by moorey

Hmmm, this just shows me how little I know. Much appreciated for that, i'll show it to a mate with a brain and see if he can help me.
Cheers for that

If you draw a simple sketch of both radius arms, looking from the side.

Imagine the left side on full bump travel and the right on full droop. Then a sketch of the radius arms will show the axle end of the left arm is high and the right is low.

The angle between the arms is considerable, which means they are trying to twist the axle housing, but the housing tries to resist being twisted, thus acting as a large sway (anti-roll) bar.

The only way that you get any articulation with radius arms is through flex in the bushes (and twist in the axle housing).

Front springs with a high spring rate, do not help articulation, nor do el-cheapo polyurethane bushes.

A spring lift, means that the chassis bush for the radius arms are aproaching binding earlier when the axle droops. The solution to this is to bend the radius arms near the chassis bush.

Lower rate springs, with longer free length, compliant radius arm bushes and a rear sway bar and disconnected front sway bar, help to balance front to rear articulation, which is the ultimate goal.

Originally Posted by Bush65

A spring lift, means that the chassis bush for the radius arms are aproaching binding earlier when the axle droops. The solution to this is to bend the radius arms near the chassis bush.

The bend makes them weak on the rear and illegal on the front. Any bent link will by design be weaker than a straight one, even it it has bracing. I wouldn't ever do this though plenty of people do. You can definately buy for the rear, and possibly for the front a replacement chassis bush and mount that is places the bush at an angle. This is a much better way of doing it.

You want one of these! A hinged radius arm:



See http://www.d-90.com/prod/hinge.html for more info.

Hmmmm, thanks again all, I see I have more to worry about than simply softer springs

Looks like some deep thought ahead about whether its worth doing anything on my budget. I already have reasonable articulation, so maybe savings should start for a diff lock
Cheers.

Moorey

The front suspension is totally different in geomerty than the rear. Its design has to deal with huge loads under braking and cornering etc, hence thats why it is designed like it is.
I used to run a hinged radius arm and Haultech bushes, but I tell you if you constantly work the suspension off road on big articulation, you will get jack of pulling it out every few months and changing bushes. More so you get horrible pulling to one side or the other under heavy braking if using softer bushes. They are great in buggies, not 2.5t 4wd's.
I now run standard bushes and radius arms, and I tell you what its not much different. Save your dollars and put a Maxidrive in the front, pick good lines and you'll have no problems.
I run an Isuzu 3.9 on progresive springs with modified turrets and 80 series shocks in our Rangie and it articulates fine with no problems.

PS I am more than happy to sell you my hinged radius arm though!!!!

Justin