PV 1962, 544 hard suspension

[142 Guy]

First observation is that the comment about the rear anti sway bar having no effect on suspension stiffness is not true under all circumstances. In situations where both rear wheels are deflected equally (hitting a rumble strip / driveway ramp) the rear sway bar has no effect. In situations where there is differential movement of the rear wheels (one wheel hits a bump on the road) the rear axle articulates causing the ASB to twist and increases the effective spring rate at the affected wheel.

Refer to the very end of this thread on PV544 suspension work where the poster recommends against the use of the IPD rear ASB for street driven cars.

https://www.californiaclassix.com/Bernard/PV544-4.html

On some cars the use of poly bushings which are very stiff can reduce the articulation of the back axle. I am not a PV expert; but, after looking at pictures of the PV rear suspension it is not obvious that stiffer bushings would have a material effect on the articulation of the rear axle. Stiff poly bushings on the PV would likely increase the transmission of noise and vibration to the body; but, would not necessarily make the suspension stiffer.

With one caveat, adding weight to the rear of the car will not improve the ride. The spring rate is the spring rate and added weight will not change that. The caveat is that if the springs are incorrect, particularly the free length is too long or if the spring rate is too high and you are topping out at the upper limit of the limit strap or the shock absorbers you will certainly perceive that as roughness. Adding weight may eliminate or reduce a topping out problem.

If you have a vernier caliper or micrometer I suggest that a better way to validate that the springs are correct is to measure the gauge of the spring wire and count the number of coils and compare this to the same measurements from a stock spring. This type of comparison is not a complete guarantee that they are correct because even with the same wire gauge and coil count the spring pitch / free length could be different; but, in order to do that measurement the coils have to be out of the car which complicates getting the stock measurement from somebody else.

One thing to check would be the limit strap. With the car un loaded is the strap at its limits? That might suggest that the strap is incorrect, incorrectly installed or that in fact the springs have a free length that is too long. Does the service manual have a specification for the free length of the limit strap that you can check?

There are a number of shocks that will 'fit' the 544. Some of them cross reference to vehicles that are grossly different from the 544 so fit does not necessarily mean suitable. You said that you switched to the original Monroes. Do you mean the original shocks on the car or new OEM Volvo rear shocks which I believe are supplied by Monroe? If you have new Volvo blue box shocks that is probably as close to 'correct' as you are going to get with an off the shelf product and is not likely the source of your problems unless the shock is defective. With a non gas shock like the Monroe it is moderately easy to operate the shock from full extension to full compression to make sure that the shock is not binding which would contribute to jarring from the suspension.