Unequal Rear Suspension Settings?

[SD1too]

Originally Posted by Kearton

Ride height is controlled primarlly by the springs, so i don't think it can be due to the shock absorbers.

Have you ever fitted shock absorbers yourself Kearton?

Simon

[Kearton]

Originally Posted by SD1too

Have you ever fitted shock absorbers yourself Kearton?

Simon

Not on a car.
If you need to do, it I think it will be easier on the rear than the front as the springs are housed separately, so there is no need to remove them.

[KWIL]

Springs should be replaced in pairs to ensure equal performance. Shocks do not set ride height.

[SD1too]

Originally Posted by KWIL

Shocks do not set ride height.

I see that you are a professional engineer Ken so can you help me with this please?

Whenever I fit a shock absorber I have to raise the car body very high, beyond spring-determined height, in order to insert them. When the body is subsequently lowered the spring partially compresses but so does the shock absorber. A point of equilibrium appears to be reached. Surely this would depend upon the ability of both the spring and the pressurised shock absorber to compress, wouldn't it?

If I removed my shock absorbers completely, would you say that the car's body height would be identical to that with the spring/shock absorber combination fitted?

I'd be grateful if you could explain where I am going wrong with this.

Simon

[dave lincs]

Originally Posted by SD1too

I see that you are a professional engineer Ken so can you help me with this please?

Whenever I fit a shock absorber I have to raise the car body very high, beyond spring-determined height, in order to insert them. When the body is subsequently lowered the spring partially compresses but so does the shock absorber. A point of equilibrium appears to be reached. Surely this would depend upon the ability of both the spring and the pressurised shock absorber to compress, wouldn't it?

If I removed my shock absorbers completely, would you say that the car's body height would be identical to that with the spring/shock absorber combination fitted?

I'd be grateful if you could explain where I am going wrong with this.

Simon

I would think the answer is obvious but as the clubs technical advisor why don't you make it Simple Simon and remove your shock absorber and try it then you can let us all know

[xsport]

Another point is that if the shocks are not equal length when fully extended , then this will give a different ride height. I had this problem when i bought new shocks. The seller listed them as suitable for rover 75. They were in fact the mgzt rear shocks,which were shorter,as are the springs. Apparently , the last R75 used the mg set up on them, ( contempory models ) so ,if the shocks or springs are not the same each side , it will. Unless they were all renewed in pairs of the same,then you will have ride height differences. Even heavy duty springs (which i have fitted on the rear) sit much higher. When shorter shocks are fitted ,or shorter or stronger springs fitted, then they are already compressed lower than the originals. Simon has made a reply request,which i am interested in too ....

[sworks]

It’s as simple as….
The springs are there to carry the weight of the vehicle and provide up and down movement of the suspension whilst keeping the vehicle level and to carry the weight of the vehicle. The ride height is regulated by the spring hence why you get ‘lowering’ springs. The damper is there to control and ‘dampen’ the operation of the Spring and in doing so keep the wheel on the road. The dampers are not weight carrying.
You can get lowered or shorter dampers but these aren’t to do with the height of the vehicle but the height of the spring, a lowered spring needs a shorter damper to control it effectively.

[xsport]

Yes agreed. But everything mentioned in the past posts will depend upon having the correct shocks and springs fitted , and that they are all functioning equally and correctly. We wont know this until this status has been confirmed from the original poster. Variants in springs and shocks will bring different ride qualities and properties ,but most importantly is that they are equal each side .Thanks sworks for the post. ...

[SD1too]

Yes, thanks Mark and Kearton.

This is the interesting bit.

Originally Posted by sworks

The dampers are not weight carrying.

I understand what you're saying Mark but if that was absolutely true wouldn't it be possible, with the car resting on its wheels, to undo the damper's fixings and just slide it out? But that's not possible.

As Kearton has said, the damper is partially compressed. It contains gas under pressure so doesn't that provide some support to the body, albeit much less than the spring?

Simon

[Kearton]

Originally Posted by SD1too

I see that you are a professional engineer Ken so can you help me with this please?

Whenever I fit a shock absorber I have to raise the car body very high, beyond spring-determined height, in order to insert them. When the body is subsequently lowered the spring partially compresses but so does the shock absorber. A point of equilibrium appears to be reached. Surely this would depend upon the ability of both the spring and the pressurised shock absorber to compress, wouldn't it?

If I removed my shock absorbers completely, would you say that the car's body height would be identical to that with the spring/shock absorber combination fitted?

I'd be grateful if you could explain where I am going wrong with this.

Simon

Try a static damping test: Stand beside one corner of your car, push it down hard & then let go. When the spring pushes the body back up it overshoots the normal (rest) position then drops back to it. This is correct damping.

Explanation
When a car is sitting in its normal position (rest), the suspension must be partly compressed. (Typically by 1/3 of its travel as I understand it.) This is so that the body can move both down and up relative to rest when it goes over bumps.

A) If the damper were at its longest position when the car was at rest, when depressed it would go down, rebound to the rest position, then hit the top of the damper and break it.

B) If the damper were at its shortest position when the car was at rest, when you pushed down it would not move as it would be acting as a solid rod, giving a very uncomfortable ride.

An Aside
Drag racing cars often have rigid or very stiff dampers so that they don't compress when starting off so that the weight on the wheels, and hence the grip, is better.

I hope that helps.