1953 Skylark Front Knee Action Shocks

[Guest mdwhit]

Hi everyone,

I just got my front shocks back from a re-builder, and I was wondering if I could get some comments as to how they should function.

In bench checking the up and down strokes I found that both shocks seem matched. But they have much more pressure when I try to pull the arms up, than when I push them down.

I was under the understanding that the opposite should be true. The downward movement should require the most pressure, and that it should take around 10 seconds for me to push the arms fully down. The shocks that were rebuilt take about 4-5 seconds to push fully down, and about 7-8 seconds to pull fully up.

I realize this test may be somewhat subjective, because it depends on the strength of the individual doing the pulling, but I'm about average in strength. Also, if I had a way to securely hold the shocks on the bench, I could probably do a more accurate test.

I do have another shock laying around that takes about 12 seconds to pull down, and about 6 seconds to pull up, and this seems about right to me.

Also, I did noticed a "gurgling" sound when I did some of the strokes. Is this normal? If they happen to be low on fluid, will any jack oil or motorcycle fork oil be ok to use?

Thanks for taking the time to read through this, and any comments would be greatly appreciated.

Michael

[51dyno]

Check with the rebuilder as to what oil he put in!

[Guest mdwhit]

Check with the rebuilder as to what oil he put in!

51 Dyno,

The oil feels to be the same viscosity as what's in a bottle that I had bought from yet another re-builder a while back when my shocks were leaking. It also appears to be identical to jack oil. Thanks for the reply!

My biggest concern at this point, is whether the "up" & "down" resistances are correct. I was told in the past that the downward travel of the arm should offer greater resistance than the upward travel. I was also told that the downward travel on the bench should take about 10 seconds to pull down.

Please, any comments on this would be greatly appreciated.

Michael

[old-tank]

My guess is your shocks are correct for that Buick. For instance in the past before gas charged shocks, Monroe 'Monromatics' were soft on compression, but had much more resistance on rebound; Gabriel 'Striders' had great resistance on compression and rebound. The Striders improved the handling on a stock suspension 71 Buick, but it did not 'feel' like a Buick. The rear lever shocks on my 55's have what seems to be more rebound resistance than compression. Stay away from higher viscosity motorcycle fork oil...I tried it and broke a link on one of the rear shocks.

Willie

[Guest mdwhit]

My guess is your shocks are correct for that Buick. For instance in the past before gas charged shocks, Monroe 'Monromatics' were soft on compression, but had much more resistance on rebound; Gabriel 'Striders' had great resistance on compression and rebound. The Striders improved the handling on a stock suspension 71 Buick, but it did not 'feel' like a Buick. The rear lever shocks on my 55's have what seems to be more rebound resistance than compression. Stay away from higher viscosity motorcycle fork oil...I tried it and broke a link on one of the rear shocks.

Willie

Hi Willie,

Thanks for the input. I hope you can help me get the following straight in my head... When you say the 'Monromatics' were soft on compression, that means when they are closing, right? I'm thinking this, because the "Monromatics" are tubular and inside the spring, but since my knee action shocks are on the outside of the spring (outboard of the A-Frame), compression would mean that the arms are traveling upward, right?

If I am thinking straight on this, that would mean that mine should be softer on the upstroke of the arm, and more resistant on the down stroke. If that's the case than it sounds like I do have a problem. My knee action shocks on the bench take me 9-10 seconds to push the arms up, and only 4-5 seconds to pull the arms down.

So if the compression is the "upstroke, then my shocks are opposite of what they should be. This sounds to me like it would translate into a "thud"when I hit a pothole and a "loose" rebound as the car recovers.

I appreciate your patience in reading this, and I hope I'm not sounding too much like an idiot here:D... I don't know why, but sometimes I have a hard getting my "head" around a concept.

Thanks,

Michael

[old-tank]

Michael ---

My concept of 'compression' is as in compressing the spring and shortening the tubular shock, and in your case raising the free end of the upper control arm with the integral shock. In your case you have more resistance on compression than rebound. Ask the rebuilder if they know how 'it is supposed to be'. In the real world they will probably work fine...of course it is a pain to 'try them out' in your case. Modern gas charged shocks seem to have considerable resistance on compression and rebound until the gas charge is lost, then only on rebound.

Willie

[MrEarl]

Just curious, are these '53's

2 Vintage Kimco 1954 1955 Buick Suspension Shock Absorbers Rebuilt Set 3 | eBay

[38Buick 80C]

I'm with Willie in thinking a Buick would be soft in compression and stiff on rebound (so not what you are describing). Keep in mind a shock's resistance is relative to the speed at which the wheel is moving up or down relative to the chassis (not the speed of the car relative to the road). I mean with the slow pressure you are putting on the shock like you are doing you may only be getting the bleed of the fluid through the "piston". Effectively you are stimulating performance on a nice smooth highway and on a nice smooth highway softer compression and stiffer rebound sounds about right to me. Not sure how you would test/simulate in your garage, by hand hitting potholes or rough road conditions you'd have to be able to apply great force quickly to the shock.

The gurgling is probably the fluid passing through the "piston".

PS I keep putting piston in quotes because I have not seen the inside of a knee action shock but equating it to a tube shock the piston would be what the fluid passes through and creates the resistance.

Edited March 20, 2013 by 38Buick 80C (see edit history)

[Guest mdwhit]

Michael ---

My concept of 'compression' is as in compressing the spring and shortening the tubular shock, and in your case raising the free end of the upper control arm with the integral shock. In your case you have more resistance on compression than rebound. Ask the rebuilder if they know how 'it is supposed to be'. In the real world they will probably work fine...of course it is a pain to 'try them out' in your case. Modern gas charged shocks seem to have considerable resistance on compression and rebound until the gas charge is lost, then only on rebound.

Willie

Willie,

Thanks for the clarification... so it looks like I was understanding what you were saying.

I have tried talking to the builder about the compression and rebound stroke resistance, and unfortunately, he doesn't really know "how" they should be. He can only state "that he has re-built a lot of them" and has never had any complaints. He tells me that that he cleans the valves inside the shocks, but that there is no way to adjust them in order to control the movement.

This is the second set that he has sent me. One of the shocks in the first set had leaked hydraulic fluid all over in the box it was packed in. Also, the arms were very easy to move both up and down on that shock. The other shock was ok (not leaking), and in addition, the compression movement on my bench test took about 6 seconds, while the “rebound” movement took about 12 seconds, which seemed about right to me.

As Brian (posting below yours) has pointed out, my “bench testing” is probably not the best way to test the resistance. I got the bench testing idea from a guy at Apple Hydraulics a while back. I am wishing I had sent the shocks to Apple to begin with, but I was attempting to save a little money.

I guess I am a little unsure as to what my next move should/will be. I guess it's possible that the shocks will be be okay (or at least acceptable) if I go ahead and mount them, but I am not very confident of this scenario. They also are not much fun taking off and putting on again (especially when dealing with nice newly painted chassis components). Another “wrinkle” here is the fact that although I am trying to assemble the front suspension, it will be at least a year, or so before I get the engine in, and the front end back on the car. So any kind of testing is a problem.

Thanks again for your help,

Michael

[Guest mdwhit]

I'm with Willie in thinking a Buick would be soft in compression and stiff on rebound (so not what you are describing). Keep in mind a shock's resistance is relative to the speed at which the wheel is moving up or down relative to the chassis (not the speed of the car relative to the road). I mean with the slow pressure you are putting on the shock like you are doing you may only be getting the bleed of the fluid through the "piston". Effectively you are stimulating performance on a nice smooth highway and on a nice smooth highway softer compression and stiffer rebound sounds about right to me. Not sure how you would test/simulate in your garage, by hand hitting potholes or rough road conditions you'd have to be able to apply great force quickly to the shock.

The gurgling is probably the fluid passing through the "piston".

PS I keep putting piston in quotes because I have not seen the inside of a knee action shock but equating it to a tube shock the piston would be what the fluid passes through and creates the resistance.

Brian,

Thank you for you comments. You make a lot of sense concerning the problems with the “bench” testing (so I believe I need to consider this in my evaluation). A fellow my Apple Hydraulics had told me that if I put them on a bench, they should take around 10 seconds or so to decompress. He also stressed that a little less than 10 seconds may also be acceptable, a long as both shocks are even. At this point, I wish I would have sent them to Apple, but I was attempting to save a little money. As I mentioned to Willie in reply to his comments, I am not sure what my next move will be, and the fact that the engine and front end will not go on for at least another year, makes testing a problem.

Your explanation of the gurgling sound makes sense too. Actually, yesterday after moving the arms up and down several times, the gurgling stopped. So I guess it could have been air in the “piston” area.

Thanks again for you comments

Michael

[Guest mdwhit]

Lamar,

Wow! I go excited when I saw your link to the shocks on ebay, but darn, unfortunately they have a different mounting hole configuration than mine. My shocks have 3 mounting holes; 2 on the end away from the arms, and 1 hole in the center.

Thanks for letting me know though. If they were like mine, I believe I would be bidding on them!

Michael