Hans, I've now reset the carrier distance to 158mm but must say that I didn't notice any difference whilst I was running the car with the carrier some 20mm closer than it should be. I think I must of done at least 5,000 miles like that.
David and Forum,
The design of the rear swing-axle on Mercedes cars of the 50's and 60's (last year of manufacture was 1972) is somewhat complex, and is of course
a result of many hours of design and test work at the M-B Factory.
I enclose a text by Chris Johnson below, I have edited the text somewhat (sorry Chris...)
/Hans in Sweden
Swing axle geometry 1960’sThe geometry of the swing axle design of the Mercedes cars of the 1960’s is quite intricate. The angle of the swing axle hinge pin in the vertical plane
is very important, especially for the ”feel” of the vehicle.
Since the pinion shaft and hinge pin are forced to swing in the vertical plane together, a change in the angle of the hinge pin implies an identical
change in the angle of the pinion shaft, compared to the ground plane. This angle is determined by the vertical carrier arm, 90 degrees to the left
axle tube. This arm goes up to a large rubber mount in chassis structural beam, visible in the luggage compartment of the car.
The attitude of the hinge pin/pinion shaft is changed by sliding the upright carrier arm, either in or out on the rubber carrier bushing's outer sleeve.
This is set by loosening and tightening the two pinch bolts. The further out the carrier arm is away from the axle assembly, forward along the center
line of the car, the more "up" attitude the hinge pin and pinion shaft will have. The further the carrier arm is in towards the axle assembly,
rearward along the center line of the car, the more "down" attitude the hinge pin and pinion shaft will have.
The ideal situation is when the carrier arm is positioned such that the center line of the hinge pin would pass through the inner end of the
radius of the arc that the rear axle trailing arms would move through while the car's suspension is in its "steady" state (neither compressed
or extended) (This is a fancy way of saying that the center line of the hinge pin is parallel to the center line of the car, assuming that the ride
height of the car is correct). The position of this arm is specified to +/- 1mm in the workshop manual/book of tables (See Section 35-4).
Think about what has to happen when the rear suspension is compressed or extended. The outer ends of the axle tubes HAVE to swing
through the arc dictated by the trailing (radius) arms, but the relative height of the hinge pin is held constant (almost). This means that not
only are the ends of the axle tubes swinging up and down, but must also swing FORWARD to follow the arc of the trailing arms. In order
for the axle tubes to swing forward, the angle of the hinge pin must also change. When the suspension is compressed, the hinge pin is
forced to point down in the front. When the suspension is extended, the hinge pin is forced to point up in the front.
The problem comes about when the centerline of the hinge pin does not intersect the inner end of the radius of the arc that would be followed
by the trailing arms. Said another way, the centerline of the hinge pin is not perpendicular to the tangent of the arc. In this case, before the
suspension can be extended or compressed, the attitude of the rear axle must be forced to rotate into a position where the centerline of the
hinge pin is nearly correct, or the axle tubes will not swing. In other words, the misalignment tries to get the axle tubes to rotate around an
axis that does not coincide with the physical axis of the hinge pin.
Obviously, the axle tubes are going to rotate only around the true physical axis.
It takes a fair amount of force to "auto-rotate" the rear axle into the correct position for suspension deflection, and this force is created at the
expense of ride quality. The only reason that the suspension continues to work at all under such mis-alignment conditions is because of the
flexible rubber between all of the rigid parts. However, ride comfort and life span of components is severely affected /Chris Johnson
