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.

[Army]

I don't quite get why there is such focus on springs unless it is a common Volvo thing - different forums seem to have different concentrations of group theories.

The youtube video the OP posted (in a recent but different thread => https://www.volvoforums.org.uk/showthread.php?t=313356) showed the car not only looking very pretty (in a slick film) but driving very well. It didn't seem to me to be particularly low - it looked stock / OK to me. Still may be the magpie in me was impressed by the shiny stuff...



As said above my focus would be on the effect of adding poly bushes to a system that wasn't designed to have them.




However, looking on a few websites it looks like progressive springs are available for the PV - may be that would be a possible future upgrade? In the spirit of fairness I must admit that the existence of progressive springs being offered suggests perhaps others have had similar problems...

(I also had another thought - but haven't checked it out - but perhaps the Duett has different stiffer springs that could possibly be fitted in error?)

[Derek UK]

When the PV first came out, progressive springs weren't common or as a concept not developed much I think. Volvo never found the need to fit them to PV's, Amazons etc. The idea is good so that you can have the soft bit tackling small road imperfections. That's fine if your shocks are good enough to recognise and react to these in a proper way. I don't have a measurement for the straps but replacements from proper sources should be correct. If you make your own and you don't have one to copy you're on your own. There needs to be just a fraction of slack when the rear suspension is at at full droop. i.e. tight but not not bar tight. Tip: Make sure when you clamp up the ends they don't bow towards the tyres and scrape on the inner walls of them. It makes an odd sound which you can chase for ages. Doesn't do the tyre any good either. (Amazons too). They are just there to stop the springs jumping out on big jumps. Useful when rallying. They aren't meant to tie down the suspension movement. It would also be possible to fit the wrong length shocks, ones that are too short, and that would also limit the movement adversely. As I said, the front ones are very short and if the suspension movement is equally short it won't cope well with bad bumps.

[adarvasi]

142 Guy, thank you for your comments and suggestions. The springs are standard bought at VP Autoparts and measured against the ones previously installed, coinciding in all measurements. The shocks are Monroe Volvo PN 276442 also bought from VP.
Will check the strap, which is also new and original.
The thing is that perhaps I am expecting a softer ride that the car never provided

[arcturus]

Take a couple of friends out on the back seat for a ride and see if the extra weight makes a difference.I think that you will be surprised.

[adarvasi]

Originally Posted by arcturus

Take a couple of friends out on the back seat for a ride and see if the extra weight makes a difference.I think that you will be surprised.

I shall do that, have a good weekend

[arcturus]

An progress on the situation?

[adarvasi]

Apologies Arcturus, have been very busy with other things, have not even looked at the car; will try this week and get back to you

[adarvasi]

Originally Posted by arcturus

An progress on the situation?

Finally this week I loosen up the bushings, rode the car for about 20 km in the typical rough Mexico City streets, tighten the bushings again and no change. It’s driving me crazy. On May 18 I leave for the Rally Maya, the start is a mere 1100 km from home and then, 1250 kmof rally, and then back home, expected temperature 40/45 degrees C (no AC) so At least I would like to have a smoother ride.
The last two or three weeks I have been building a B18B engine that will be ready today and will change in the course of the week. See new post.

[Derek UK]

What tyres are you using and what pressures are you running them at?

The PV uses a rather unusual axle mount with a couple of bars and rubber bushes mounted to the diff. Other owners might like to make comments as I don't know anything about this arrangement. I'm wondering if this is isn't properly set up and is making the back end very rigid.