over the past few weeks, I have had the feeling the ride was becoming a little bouncy, more evident at slower speeds, on smooth faster roads it's not really noticeable. My thoughts are it's shock absorber related, the front struts were replaced by the dealers only a couple of years back so more likely the rears as they are likely original. The question is how do I test them?
The car sits square and the air suspension works as it should. 2007 TDV8 VSE
2003 TD6 gone.
2002 P38a gone
1999 P38a gone
1997 p38a gone
1993 VSE gone
1992 VSE gone
1966 Series 2a with V8 conversion gone

If the fronts were worn to the point of needing replacing likely the rears are as well. If it feels bouncy then it’s as good a test as anything so replace them. 2012 TDV8 Vogue (L322)

The first round of checks would be:~
Tyre pressures
Anti-roll bar drop links
Visual check of dampers for signs of oil leaks
It's unlikely to be suspension bushes as you don't mention any knocking but it'd be worth visually checking whilst you're at it.

The only way to properly check dampers is off the vehicle and comparing them to each other for compression force and recovery time, ideally also checking against a new component. I'd also say don't discount the fronts, just because they've already been replaced. The other way is to get someone to follow you in another vehicle to watch the wheels as you drive over an uneven or slightly corrugated surface, a weak damper will allow the wheel to bounce much more than it should.

I presume the front struts were changed due to air spring failure like most, but that was before my ownership. I am not about to throw money at guesses, here in Australia RR parts are stupidly expensive so I would rather spend some time identifying the problem. How does one test a shock absorber on an air-sprung car, I can only think to remove them and test resistance.
Rear bushes are all good, all front arms and bushes changed earlier this year
Tyre pressures are good
Drop links are newish and checked good
rear shocks look bone dry 2007 TDV8 VSE
2003 TD6 gone.
2002 P38a gone
1999 P38a gone
1997 p38a gone
1993 VSE gone
1992 VSE gone
1966 Series 2a with V8 conversion gone

Last edited by wayneg on 18th Nov 2022 9:57am. Edited 1 time in total

It's exactly that, but check recovery time too - if it recovers too fast, then it's worn. Dampers are the same construction for both coil & air-sprung vehicles.

Hand testing of a shock can at best reveal that it is totally worn-out. A shock test machine is required to properly test how well a shock performs but a discerning driver can do a pretty good job too, especially if the vehicle is loaded and tested on poor roads.

Along with a bouncy ride it will feel very unstable when cornering on worn shocks - often alarmingly so. The rears are cheap and easy to replace. 2012 TDV8 Vogue (L322)

I think the only people with a damper test set are the damper manufacturers, I've never seen one in any dealership and the tests listed in work instructions at best only give compression force values and recovery rate times. Things may be different for you though.

Hand testing off the car won’t tell you much as you need to be able to compress and extend the shock with a lot of force and speed to replicate the action on a car which is way more than you can with your hand. I’ve seen MOT testers check cars by lowering the lift and stopping it to see how the car bounces as it uses the weight of the car. The old test of bouncing each corner by pushing down with your body weight is ineffective on such a heavy car supported by stiff springs. 2012 TDV8 Vogue (L322)

An easy way to check the shocks (not the air bags) is to drive alongside it in another car and look at the wheels. If the shock is done the wheel will be bouncing up and down almost all the time.

After checking everything I could and with the help of a spotter the conclusion was A tyre was out of true. Finally got a new set of tyres fitted today and the ride is restored. I fitted Bridgestone Alenza 275 55 20`s having removed the strut pips and flattened the bulge in the osr arch liner. Happy to report no rubbing. 2007 TDV8 VSE
2003 TD6 gone.
2002 P38a gone
1999 P38a gone
1997 p38a gone
1993 VSE gone
1992 VSE gone
1966 Series 2a with V8 conversion gone