Rear suspension - arm geometry

[Blink]

I'm trying to find out the angles of the upper and lower suspension arms when the car is on level ground and sat on its wheels. The reason being I want to avoid the notorious spinning captive nut problem by pre-tightening the arm-to-subframe bolts before I refit the whole lot onto the car (it's a 75 saloon btw). Trying to torque up the bolts with everything on the car is impossible if one or both of the captive nuts starts spinning.

Does anyone know what the angles are?

Here's a quick diagram. The green & red lines represent the upper & lower arms - I need to know the correct angle for both.



The photo above shows the subframe as viewed from the front of the car but it's easier to look at it from the rear when it's on the car.

Like this ... (the old subframe viewed from the rear) (it's being lowered to the ground on threaded rods):

[BigRuss]

Both pairs of arms should still be able to move once the bolts are tightened correctly, that's what they are designed to do

So it's not necessary to put them at a set angle.

Russ

[macafee2]

Originally Posted by BigRuss

Both pairs of arms should still be able to move once the bolts are tightened correctly, that's what they are designed to do

So it's not necessary to put them at a set angle.

Russ

I thought that too.
In fact they have to move as the wheel goes up and down the arms have to rotate around the inner and outer bolts.

if the car sits on ramps and axle stand so it level that will give clearance to got to bolts and have the cars weight on the wheels

macafee2

[Blink]

Originally Posted by BigRuss

Both pairs of arms should still be able to move once the bolts are tightened correctly, that's what they are designed to do

So it's not necessary to put them at a set angle.

Russ

Good point Russ!! Why didn't I think of that .

I'll torque all 4 bolts up off the car and then fit subframe & arms in one go (touch wood).

Not sure about the springs though - will the arms be movable enough to squeeze the springs in and get the bottom isolators lined up correctly with the drain holes? (a relevant thread here)

Originally Posted by macafee2

....... if the car sits on ramps and axle stand so it level that will give clearance to got to bolts and have the cars weight on the wheels

macafee2

The car is up on blocks. The front wheels are still on but they're sitting on one layer of sleepers. The back end is supported by three layers of sleepers under the rear sill jacking points.

[clf]

When it is all together, have the car with the wheels off the ground supported at the sill jacking points. Then, jack below the hubs, just and only just at the point where the weight of the car begins to lift off the sill supports, then torque up the joints. Either that, or get it onto a four post lift.

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[macafee2]

Originally Posted by Blink

Good point Russ!! Why didn't I think of that .

I'll torque all 4 bolts up off the car and then fit subframe & arms in one go (touch wood).

Not sure about the springs though - will the arms be movable enough to squeeze the springs in and get the bottom isolators lined up correctly with the drain holes? (a relevant thread here)




The car is up on blocks. The front wheels are still on but they're sitting on one layer of sleepers. The back end is supported by three layers of sleepers under the rear sill jacking points.

damn, my post is not quite right but I knew what I meant, sorry. Get the rear wheels on "ramps" and axle stands under front jacking points or ramps under front wheels. This way the rear weight will be on the wheels

macafee2

[macafee2]

been thinking about this.
do the bushes revolve around the bolt or the rubbers "revolve" around/inside/outside the bushes?
If the latter then it would be better to tighten the bolts with the car sitting on 4 wheels.

macafee2

[RoverP480]

The movement is in the rubber bush, the inner tube should not move on the bolt, it would soon wear away & fail if it did. Usual instructions is to tighten the bolts with the bushes in the neutral position , load on wheels with vehicle at kerbside weight. .

[macafee2]

Originally Posted by RoverP480

The movement is in the rubber bush, the inner tube should not move on the bolt, it would soon wear away & fail if it did. Usual instructions is to tighten the bolts with the bushes in the neutral position , load on wheels with vehicle at kerbside weight. .

I'll go loosen mine and re tighten once wheels are on and the car is sitting on them.

I need to get a life, was thinking about this during the night. I knew there had to be some rotation and upon reflection was not convinced I had been right in my first post

macafee2