Shock pressure for compression
Thread Starter
Safety Car
Joined: Jul 2001
Posts: 4,871
Likes: 15
From: Detroit's West Side MI
Shock pressure for compression
I'm curious, about what is the pressure required to compress a Corvette shock, front and rear?
My rears are done and since I had them off I put them on a scale and compressed them. Both took about 50-60 lbs of force to compress, and very slowly rebounded after I removed the load (about 6 seconds to full extension).
Some old ones I had lying around took 100 lbs to compress, but the rebound was almost non-existant. Weird.
I looked all over Bilstein's page and did some searches on here and found no numbers to compare. Anyone know, or have a set of new(er) ones off the car to check? Or a website with some examples? I know valving will be different (mine are DRM coil overs and at one point were very stiff), but I'd like to see what's out there.
This is simply a science experiment, I don't need any advice...
My rears are done and since I had them off I put them on a scale and compressed them. Both took about 50-60 lbs of force to compress, and very slowly rebounded after I removed the load (about 6 seconds to full extension).
Some old ones I had lying around took 100 lbs to compress, but the rebound was almost non-existant. Weird.
I looked all over Bilstein's page and did some searches on here and found no numbers to compare. Anyone know, or have a set of new(er) ones off the car to check? Or a website with some examples? I know valving will be different (mine are DRM coil overs and at one point were very stiff), but I'd like to see what's out there.
This is simply a science experiment, I don't need any advice...
Pro
Joined: Feb 2005
Posts: 658
Likes: 1
From: Centerville OH
I am a shock absorber engineer for Bilstein.
In general, a "normal" monotube shock like a Bilstein should take approximately 80 to 100 pounds to compress it about 2 inches. This preload force is a result of the high pressure gas charge (typically 300-400 psi) that is needed to make this type of shock function.
I'm not at all surprised that your shocks extended very slowly. The higher the gas pressure, the quicker the rod will extend after the shock has been compressed. At 50-60 pounds of preload, these shocks have lost some of their initial gas charge, so they won't extend nearly as fast as a shock that has a higher preload.
Hope this helps.
In general, a "normal" monotube shock like a Bilstein should take approximately 80 to 100 pounds to compress it about 2 inches. This preload force is a result of the high pressure gas charge (typically 300-400 psi) that is needed to make this type of shock function.
I'm not at all surprised that your shocks extended very slowly. The higher the gas pressure, the quicker the rod will extend after the shock has been compressed. At 50-60 pounds of preload, these shocks have lost some of their initial gas charge, so they won't extend nearly as fast as a shock that has a higher preload.
Hope this helps.
Thread Starter
Safety Car
Joined: Jul 2001
Posts: 4,871
Likes: 15
From: Detroit's West Side MI
Great, thanks much for chiming in.
What would you estmate was the original pressure / reaction time of these? They were rebuilt in your CA office with the "Sears Point" valving.
In addition, is the failure of a monotube shock linear? In other words, does the pressure to compress and the speed of rebound for a particular valving slowly deteriorate, or do they maintain a high percentage of their original performance until a failure point?
Thanks again...
What would you estmate was the original pressure / reaction time of these? They were rebuilt in your CA office with the "Sears Point" valving.
In addition, is the failure of a monotube shock linear? In other words, does the pressure to compress and the speed of rebound for a particular valving slowly deteriorate, or do they maintain a high percentage of their original performance until a failure point?
Thanks again...
Pro
Joined: Feb 2005
Posts: 658
Likes: 1
From: Centerville OH
I don't have any specific knowledge regarding these shocks, but I can tell you that the only thing that would make them "extreme" is stiffer valving. We build the same basic design for all our products. My guess is that VB&P orders the shocks from our Aftermarket group with their own specific valve code, hence the "extreme".
Pro
Joined: Feb 2005
Posts: 658
Likes: 1
From: Centerville OH
In addition, is the failure of a monotube shock linear? In other words, does the pressure to compress and the speed of rebound for a particular valving slowly deteriorate, or do they maintain a high percentage of their original performance until a failure point?
Thanks again...
Thanks again...
However, the way the shock is used also makes a difference. Since you track your car, you are not going to see the kind of life that someone who only drives their car on the highway does.
Thread Starter
Safety Car
Joined: Jul 2001
Posts: 4,871
Likes: 15
From: Detroit's West Side MI
Thanks, that's great information.
I guess it should have occurred to me that the slow pressure I put on the shock is significantly different than the quick compression it sees in real life, as well as the quick transitions from compression to extension.
I was able to reach Ramon in CA, so I overnighted them to him and he's going to try to get them revalved by the weekend so I can make the race.
Yet another example of why I tell people around here to use Bilstein shocks...
I guess it should have occurred to me that the slow pressure I put on the shock is significantly different than the quick compression it sees in real life, as well as the quick transitions from compression to extension.
I was able to reach Ramon in CA, so I overnighted them to him and he's going to try to get them revalved by the weekend so I can make the race.
Yet another example of why I tell people around here to use Bilstein shocks...
