Calling Pine/Impi

[BARON]

Hi Guys .


Ive either never seen a late model a/c rear suspension or never payed attention to its detail.
What is this. If it is the complete rear beam for a t3/t4 or whatever does it mean that the beam is only attached to the pan at the three eyes .
(with fat rubber inserts) ----That sound a bit flimsey. Or am Im completely wrong .
What is the purpose of the "s" shaped arm if you still have the straight swing arms as on the beetle.
My t3 corpses does not have the "s" bars.
Thanks
cheers baron

[Ron&Gill]

May I?

The purpose of the S-arms of this IRS is to hold the wheel up straight, at all times. The shafts that go between the wheel hub and the gearbox have an outboard CV joint in them.

On the old T3 suspension, with the solid shaft, the wheels do not stay up straight with suspension movement.

The old T3 suspension does only attach by three points, the centre one and two at the top of the shock mounts.

It looks to me as if the IRS has two more mounting point, on the beam itself.

[BARON]

Thanks boet
But why then a flat swing arm (where the srewdriver is ) and the "s" swing arm.
Surely with cv joints on the solid axle you can still have a vertical movement.
I think I took in to much fumes this week end but I just cant see the use of two different swing arms.
cheers baron

[fig]

The "s" swing arm is, I believe, correctly called a semi-trailing arm. Its purpose is as Ron said. The "flat" swing arm is called a spring plate. The spring plate provides the pivot point for the torsion bar, so you have springing. The semi trailing arm is simply there to keep the hub in its correct position (ie, to keep the wheels vertical).

The earlier swing arm design with the straight axle meant there was always a constant 90deg angle between axle and wheel, but the downside was suspension movement affected wheel camber (ie, the wheel was not always perpendicular to the road). Adding the second joint in the axle meant that the angle between axle and wheel was variable, so another mechanism was needed to hold the wheel upright, hence the semi-trailing arm.

[IMPI]

That is a type 3 rear cross member the s shaped arm bolting to the crossmember (torsion housing) eliminated the swivel point where the swing axle entered the gearbox and moving it parrallel (almost to the axle ) thus eliminating severe camber changes.
the type 3 torsion housing is mountd to the pan in 3 places the center as well as the two on the torsion tube the other two mounts are directly to the body above the shocks. all type threes used this setup so the parts are interchangeable.