18 replies to this topic

[cal844]

I have a set of Spax Krypton 14 point adjustable shocks which have been lying a few years(looking to use them on my estate)

They go from full length to full compression very easily(tested at numerous settings)

However the issue is they don't rebound, I have to manually operate them? Is this correct?!!

[nicklouse]

yes

 

but I would be wary of no change in feel when you make adjustment to the adjuster.

Edited by nicklouse, 15 May 2017 - 10:49 AM.

[cal844]

yes
 
but I would be wary of no change in feel when you make adjustment to the adjuster.

Sorry, I should have said they feel stiffer in rebound, again differing between settings

[nicklouse]

then no issues.

[cal844]

then no issues.

I know this may sound silly but with any other shock/strut the usual test is to compress it and see if it rebounds,

these are very weak on compression but stiff on rebound

This is correct for this type of shock, yes?!

[tiger99]

There is a very common misunderstanding, caused by the behaviour of gas-filled dampers that do extend themselves, all that dampers should rebound when compressed. A true damper does not, it only opposes movement, and the faster the movement, the more force it opposes it with. The vast majority of dampers, including most common varieties on the Mini, do not contain pressurised gas, and as such will stay where you last left them, or droop slowly due to gravity. The rebound action when you bounce a car is caused by the springs or rubber cones in the case of the Mini, never the dampers, which by the way are not struts.

 

However in your case they are so-called Krypton dampers, and Krypton is an inert gas. It is actually a rather pathetic marketing gimmick, as Krypton is expensive and Argon, which is cheap, would do just as well. But be that as it may, if these are supposed to be gas pressurised, the pressure is no longer there. The pressure is not there to support the car and it makes a negligible difference to ride height, but it is essential to make the oil in the damper go where it needs to on the rebound stroke. So if they really are gas pressure dampers, and there is no pressure, they are utterly useless. They should need a fairly firm push to compress them fully.

 

I suggest contacting Spax to see if they can be re-gassed.

 

https://www.google.c...YhnTAnWlINN49MA

[cal844]

There is a very common misunderstanding, caused by the behaviour of gas-filled dampers that do extend themselves, all that dampers should rebound when compressed. A true damper does not, it only opposes movement, and the faster the movement, the more force it opposes it with. The vast majority of dampers, including most common varieties on the Mini, do not contain pressurised gas, and as such will stay where you last left them, or droop slowly due to gravity. The rebound action when you bounce a car is caused by the springs or rubber cones in the case of the Mini, never the dampers, which by the way are not struts.
 
However in your case they are so-called Krypton dampers, and Krypton is an inert gas. It is actually a rather pathetic marketing gimmick, as Krypton is expensive and Argon, which is cheap, would do just as well. But be that as it may, if these are supposed to be gas pressurised, the pressure is no longer there. The pressure is not there to support the car and it makes a negligible difference to ride height, but it is essential to make the oil in the damper go where it needs to on the rebound stroke. So if they really are gas pressure dampers, and there is no pressure, they are utterly useless. They should need a fairly firm push to compress them fully.
 
I suggest contacting Spax to see if they can be re-gassed.
 
https://www.google.c...YhnTAnWlINN49MA

I shall try that thanks again Tiger :)

[nicklouse]

think you will find they are not pressurised.

[cal844]

think you will find they are not pressurised.

So they need regassed?

[Spider]

think you will find they are not pressurised.

 

Correct. They aren't pressurised and so won't extend on their own.

 

They should be stiffer on the compression stroke than the extension stroke, that's normal.

 

In general, they sound like they are in usable, condition.

[nicklouse]

 

think you will find they are not pressurised.

So they need regassed?

 

nope.

[nicklouse]

Just to expand on this. As we know shocks are not full of oil. There is a void. This is normally filled with air.

But this can cause cavitation. The air being held in the oil and coming out as the oil is squeezes through the damping plates/orifices etc.

Using a heavy gas instead of just air can help reduce the cavitation.

Nothing more/nothing less. Nothing pressurised.


Oh for a technical description on cavitation look it up. It is quite fun and I don't know the details. Like how does the air appear out of the water at X 100 or 1000 feet underwater with just a propellar to create it?

[cal844]

think you will find they are not pressurised.

So they need regassed?

nope.

Perfect!! They're on the car anyway, only took me 4 hours lol

[Spider]

Nothing more/nothing less. Nothing pressurised.
 

 

Some do have pressurised gas - not Spax though - and this is done to increase the temperature at which the onset of 'airation' and boiling point of the oil happens.

 

These shocks do generallyextend under their own pressure but they do not have enough pressure (or shouldn't) to raise the height of the vehicle on their own.

 

As a side note, the shock on my off road Mokes I have made to my own specs. The fronts we set up the prototype on a test rig and ran continuously for 3 days from full compression to full extension in 1.2 second cycles.

 

After 2 hours, the sticker fell off. By the end of the first day, the paint had blistered. The next morning, the body had turned blue from heat.

 

And no measurable loss of performance by the end of the 3rd day.

[nicklouse]

 

Nothing more/nothing less. Nothing pressurised.
 

 

Some do have pressurised gas

 

yep.

 

and here is the start of the confusion. gas filled and gas pressurized.

 

Not the same.