Hi everyone, is the way to test second hand shock absorbers to compress them and see if they rebound by themselves? I have some from an old volvo(they have only done 100miles) and are the right lenght for the front of the moggy. But they dont re-extend. :xconfused
cheers, michael.
they should be fine, the only real way to test shocks is with a shock dynomometer but if you are doing it by hand the way to get a clue to the condition is to check for leaks, make sure there is no free play and to try and make sure the resistance is consistant throughout the shocks travel.
The bilstein shocks on the back of the 323 are nearly too stiff to compress by hand :D
:rolleyes:
If a shock does not rebound(extend on it\'s own).. Then it is no good!
Basics really..
So one person says they are fine? and the other rolls their eyes at me!
Anyone else have an opinion.?? they do not leak and are consistantwith pressure. But alas not self return......
Quote from: TRex:rolleyes:
If a shock does not rebound(extend on it\'s own).. Then it is no good!
Basics really..
Not all shocks return on their own ... explain why they should ?
Thats basic common sense mate..
How does it dampen then? It absorbes/cushions the/a load by going down, if it stays down then what? :rolleyes:
If you want to go silly and say thats what the springs are for... then yes the spring does bring it up, but if the shock does not return on it\'s own strength then it is useless as a complete damping force.
Lets put it this way, why bother with shocks then, just use springs!
Now if you think about that, or \'had experience\' you would have a vehicle that is totally unstable as it will be bouncy as hell, there is nothing to control the springs damping/bouncing rate.
Or if as \'you said\' shocks work only on compression(going down), when you hit a severe ditch/bump the springs will compress and absorb the impact nicely and then shoot the bloody car up in the air as there is no resistance to control the spring rate on the rebound!
Again basic common sense....
If you want more infomation or want me to go deeper on this subject just ask.
As it seems over 50 people have viewed this thread and no one knows!
Sorry chaps.
A shock absorber has oil in it. The oil is in 2 "chambers". They are connected by a small orifice, so the oil can go from one side to the other, but only very slowly. In this was the shock absorber resists movement when being compressed and decompressed. Yes, some shock absorbers do have springs in them, but I dont think they all do.
Travelling Bob, do they resist movement in both directions?
Here is a diagram from "how stuff works" -
Quote from: MartinySorry chaps.
A shock absorber has oil in it. QUOTE]
Obviously not aimed at me! ;)
I think you have just confused things saying this below mate...
{quote}Yes, some shock absorbers do have springs in them, but I dont think they all do.{quote}
I won\'t correct or try to explain that...
But this is a very good place for people to learn things before posting incorrect stuff here... \'click click\' (http://auto.howstuffworks.com/car-suspension5.htm)
Quote from: travellinbobHi everyone, is the way to test second hand shock absorbers to compress them and see if they rebound by themselves? I have some from an old volvo(they have only done 100miles) and are the right lenght for the front of the moggy. But they dont re-extend. :xconfused
cheers, michael.
Hi Michael,
Back to your question.
With no springs fitted, if the center rod is hard to push in and pull out it should be fine.
Hope this helps
Won\'t go into details anymore on how \'shock absorbers\' work as it\'s very simple and covered in above examples..
I\'ll offer a write up on what people love on here..... \'Drag racing\' and the Shock/Spring set up that\'s best. How it works and why...
This will also help understand more about what I was earlier explaining about damping, spring rates and how spring rates are required in different conditions etc..
For drag racing, specialty shocks play a big part in chassis dynamics.
Front shocks with very soft "rebound" settings allow the front end to rise, changing the rate of weight transfer to the rear tires to improve traction. Adjustable shocks allow you to control the rate at which that weight transfers.
While non-adjustable stock replacement shocks do an adequate job of improving handling over worn-out original shocks, when it comes to high-performance applications, stock shocks are often found wanting.
Starting with drag racing, this situation actually requires shocks for the front and rear that are often much softer than stock. For a typical street/strip car, you\'re looking for front shocks that allow easier front-end travel to establish a given rate of front-end rise to help weight transfer to the rear tires.
Rear shocks are also important in this traction equation, and also offer a slightly longer extension to prevent bottoming out the shock when planting the tires, especially with suspensions with an excess of 100 percent antisquat when there is separation between the tire and the body at launch.
""The last thing you want is for the rear shock to bottom out, which will cause instantaneous tire spin."" These shocks are usually single-adjustables, although you can invest in specialty coilovers that are double-adjustable.
Drag-racing shocks are also referred to in a slightly different way than most other shocks. Often you will read references to rear shocks that are 50/50 or front shocks that are 90/10. Basically, these are references to the amount of force applied by the shock to resist movement. In the case of a 50/50 shock, the resistance is the same in both \'compression and rebound,\' while a 90/10 shock has nine times the resistance to compression than it does to rebound.
The 90/10 is almost exclusively a \'front shock\' designed to "extend (rebound)" very easily and offer significant resistance to compression. This allows the front end of the car to rise very quickly and easily and then maintain that front-end rise throughout the entire run.
Better handling on your favorite twisty primary highway calls for a whole different set of shock requirements. Generally, this can start with a shock absorber that is shorter in length because the vehicle has been lowered, but also because the amount of suspension travel is greatly reduced.
"These shocks are almost the opposite of the drag shocks," since rebound damping is greatly increased given the increased spring rates that road-race-style cars generally employ.
This is another area where adjustable shocks are an excellent investment.
Up to a certain point, a stiffer shock, especially in rebound, is advantageous. But there also comes a point where a stiff shock will not allow the suspension to react to ruts or tall bumps. This stiff rebound allows the tyre to skip over the tops of a series of bumps such as a speed bumps, exit ramp. When this happens, the tyres physically lose contact with the road, which means you\'ve just lost all traction. This is quickly followed by a possible spin.
If you\'ve ever driven a car with too-stiff shocks, you know this is an extremely disconcerting and evil situation. This is yet another reason why adjustable shocks are a good idea. Another situation that can affect this is when you change to significantly lighter-weight wheels and tires on an otherwise optimized shock package. Suddenly, the car is very skittish because of the reduced unsprung weight.
:( just realized how much was typed there..
Hope this helps anyways...... off for a break....
Quote from: TRexWon\'t go into details anymore on how \'shock absorbers\' work as it\'s very simple and covered in above examples..
:( just realized how much was typed there..
Hope this helps anyways...... off for a break....
Thanks for all the typing, as lots of people don\'t know this stuff,
well done :)
Thanks,
Now lets see those drag launch times :burnout
Trex
A gas filled shock should re extend when compressed due to the pressure inside of it and the different areas of the top and bottom of the piston (think about it the top side has a socking great damping rod affixed to it) Many older shocks and OEM ones are NOT gas pressurised. (1st gen rx7\'s for example) and do not re-extend on their own
The oil in these shocks are not under any sort of pressure unless being used and should not return by themselves.
WOW, thanks for the replies. The shocks are monroe brand. Oil filled, no spring. They were off a 1970 volvo 144. Rear fitted and coupled with factoey springs. There is resistance when pushing down and also when trying to pull back.
I cannot afford a coilover conversion on the front of the moggy so am trying to use me scone and find an alternative.
Thanks for hte help guys.
cheers, michael.
TRex, I appreciate the effort you\'ve put into the thread about how "shock absorbers" work, but I think it confuses the difference between springs and dampers. The spring is there to absorb the shock, but as it has no way of getting rid of the energy it rebounds and, as you said, you end up bouncing down the road if you have no damping. The damper (unfortunately AKA shock absorber) is there to absorb the energy of the shock, both in compression and rebound; it doesn\'t necessarily re-extend in isolation as it\'s the spring which causes this in normal operation.