A bt of a headscratcher .....

My car had a professional geo and a corner weight a few months ago. Afterwards, the platform heights on the dampers were pretty much equal either side on each axle just as you would expect. I drove the car for a bit but then one dayt found that one side had sagged and the ride height had dropped by over 1cm on that side .... very noticeable even just casually eyeballing the car.

I went underneath again and pulled everything apart and swapped each spring round from one side to the other. I also checked my install and all my top mounts, the spacers and the position of the bearings in my top mounts which was all perfect.

After the spring swap initially the problem seemed to go away but after 100 miles or so it's now returned and the SAME side of the car has dropped again by 1cm. So that definitely rules out the springs then.

The exposed threads or the platform heights are still pretty much equal either side. It's NOT a corner weight thing because if I go in and adjust the platforms to raise the sagging side upwards so the car is level again, the plaforms on the sagging saide are way way higher, like 10 threads or more ! That shouldn't be the case. I have also gone over the top mounts, the top hats and teh spacers with a fine tooth comb and all of this stuff is simply locked into a fixed position that is the same on both sides. There is no discrepancy here and nothing has been damaged or flattened or compromised in way. The chassis is obviously ok and the slots where the top mounts bolt into are the same as when the car left the factory ! The uprights at both ends are obviously as they should be and the same both sides so there is no way the ride height could be affected by anything there.

So the only variable now is the damper. I always thought that springs do all the supporting but in this instance the only explanation can be that the dampers also do some of the supporting and in my case, two of them on one side have lost some of their valving or internal pressure ?

I've owned a ton of performance cars over the past 25 years and never had anything like this. Has anyone experienced something similar ? Any guidance would be appreciated. Maybe there is something I have missed and that its not the fault of the dampers but I cant think what else.

 

Which side seems to sag ?

Level at rest (ie: no one in the car) has not been my experience. I assume when the car was corner balanced they had drivers weight in the seat. Especially with PSS-10 relativly light springs, and me being a big guy (220lbs) drivers side was noticably higher with me out of the car. 10 turns sounds about right to me.

 

The side that is sagged is the drivers side so I can see what you are saying but that is completely the opposite of what you would expect. Besides, all my observations of sagging are with no occupants. Put an occupant in there and it will just make the sagging worse. This is nothing to do with corner weighting. Imagine that coner weighting was never done. When the car was geo'd and the ride heights done the car looked properly at RS height on both sides. After it sagged it was then 1cm lower on one side. It sagged just through driving, nothing was changed. So regardless of any corner weighting compliactions, one day the ride height was correct and the next it was 1cm lower one side at both axles. In any case, I only weight 11 stone and whenever I've had a car corner weighted you can barely see any difference in ride height whether I am in the car or not, even on a 500kg caterham I once had.

 

Ok, i think this is definitely a damper problem.

I just went outisde and got the front wheels off and the car jacked up 2 feet off the ground. With the front suspension in full droop and no wheels I measured variious lengths, top hats to end of damper, underside face of top mount to end of damper body, length of both springs etc.. and everything is the same on both sides.

Then I compressed both front dampers with a trolley jack underneath the steering arm. Basically there is something definitely wrong with one side. When I compress the correct ride height side the damper and spring compress nice and easy and in a progressive neat fashion and fairly quickly you can compress it no more. When I jacked up the other side (the sagging driver side or 'offside') the damper seems to make heavy work of it and it takes a lot more work on the trolley jack to compress everything. The car body starts to lift up and it doesn't seem to compress fully. When it seems to compress no more the actual length of both springs is longer than the other side by almost half an inch. The platform between the helper and the main spring also starts to rotate awkwardly as well. The damper on this side basically won't compress fully or at least does not compress in the same way as the other side.

 

They are a gas pressure shock, the gas pressure is significant and will affect ride height

Sounds like the gas pressure in one shock is sub par

 

Interesting,
I have PSS10's
I had a similar problem, on the road the car looks great, but in my garage one side front was always higher than the other, the garage floor is dead flat
So this got me thinking, my driveway is steep and angled, could this cause the problem. Yes

So from what I can work out, when I drive the car down the drive way, it contorts the suspension and then park the car, as there is no apposing force on the PSS10's, it sat in that contorted position. Well at least for some time.

Interesting that the side the dampers are squashed is low and the side stretches is long and this is how it sat in the garage.

This problem did have me thinking for around six months, I don't really check out my car on the road, but certainly do in the garage, considering I had it professional corner weighted and height adjusted.
It was a real brain teaser.

I would check this issue for your problem, not saying it is your fix, but was certainly my problem.

Good Luck.

 

Neil, thanks for the input but the first thing I did when this happned was to turn the car around on my drive the other way. If I parked the thing on a 45 degree cambered road it would still be lower on the drivers side ! Besaides, OPC measured the ride height from the proper datum points on a flat floor and it was 1cm lower a few weeks after they had got it perfect on the very same jig.

Bill, thanks, yes it definitely looks like an internal problem. What a shame. All I wanted to do was drive my car for this year and the next. The annoying thing is the labour to take it all off, refit it and then pay for yet another geo and ride height. That's well over £1000 and not through any fault of my own. These shocks have done less than 4k miles and aren't even a year old so I think I will look to fit something else. I have a 180,000 miles volvo outside and the shocks on that havent sagged.

 

Andreas

 

Hi
A shame it was not that, worth letting you know.

As I understand PSS10's have a life time warranty, maybe you can clam warranty.

 

Yes, I will certainly claim warranty but it won't change the massive bill for all the work and yet more time lost with the car up on axle stands.