Gas Springs for Rear Clip

Got the gas springs/struts installed on the rear clip, but think I ordered them with way too much pressure. Ordered two 125 lb struts. Clip definitely stays in place in the up position, but takes a lot of prssure to push into closed position, and when it gets to closed, it immedaitely starts to go up unless it is latched in place or you hold it down.

What "poundage" gas springs/struts are folks using to easily lift rear clip, hold it in place, and then easily lower on to latching pin?

Thanx
Mark
 
Bought mine from Olthoff. Don't know the poundage of the strut and car isn't w/ me right now to check. The one's from Olthoff work great. Give him a call. I'm sure somebody there will know.
 

Seymour Snerd

Lifetime Supporter
Got the gas springs/struts installed on the rear clip, but think I ordered them with way too much pressure.
I just installed Olthoff's kit the other day and one thing I discovered is you get very different results depending on where the lower ball bracket is. Olthoff specifies 8.5 inches forward of the rear subframe cross bar using the struts he provides, and in that position mine work fine.

For various reasons I tried it a few inches forward of that and the action was far to stiff, something like what you describe. So if you can, try moving the lower mounting point to the rear, maybe an inch at a time. That in effect gives the clip more leverage over the strut. One way to do that is to c-clamp the bracket to the square tubing, although be sure the c-clamp is tight.

Also, be sure you start out with the clip able to open all the way, such that it reaches a balance point. At this point the rear deck just forward of the spoiler is 30 degrees from vertical. Initially I was not able to open it that far but it was because the hinges were adjusted low so the lower edge of the clip hit the subframe before it got fully open. So for experimenting purposes you may want to adjust your hinge eccentrics all the way up or all the way back. You will later need to come back and adjust them so the center hole lands on the pin, but that's a detail.
 

Seymour Snerd

Lifetime Supporter
Mine are marked AVM industries: 4684 and in smaller type 36509. They are 21-1/4” long, center to center when extended.
 

Seymour Snerd

Lifetime Supporter
I happened to be visiting Superformance this morning and on the floor is a pre-owned Mk II with a strut kit that appears identical to that which I got from Olthoff, except the struts were both smaller in diameter and the bottom mount further forward on the subframe, 2-3 inches to the rear of the front cross-tube. These struts are clearly a lower spring rat than what I have, and the overall action was nicer; it's balance point was a few inches above closure, and after that if fell rather gently into place. Unfortunately there were no identifying markings on the struts whatsoever. It also clearly was not putting as much strain on the subframe as my current setup does (I can see the 1" square steel tube flexing during operation). I'm not sure what to do next other than perhaps semi-blindly try different struts....
 
Hi,

I would like to fit gas struts to my car, if anyone is able to post pictures of their set up to give me some ideas I would be grateful.
 

Seymour Snerd

Lifetime Supporter
... if anyone is able to post pictures of their set up to give me some ideas I would be grateful.
Here's how it's done on an SPF Mk II (which I understand to be more difficult than a Mk I):

Rear Struts.jpg

The top of the strut is attached 16.5" forward of the rear spoiler. The bottom is attached to the subframe 8.5" forward of the rear cross bar. The key design issue is to recognize that the hinges need to be firmly connected to the point where the top of the strut attaches, since, particularly when closed, there are large forces being transmitted which the fiberglass is not stiff enough to transmit. So (as you can see on the left) a pice of 1/8" aluminum plate is used for that purpose. That plate is further bent into a shallow U for additional stiffness. It is bolted directly to the hinge using the same five bolts that mount the hinge to fiberglass, and then to a bracket at the top with four bolts (and large washers). The top bracket extends the upper ball inward to align in a vertical plane with the sub frame ball.

Of course that's all fine for an SPF Mk II rear clip with the particular strut I was provided. None of those dimensions will carry over to any other situation, so you have to deal with the geometry and forces involved. AVM Industries provides some technical guidance here: http://www.avmind.com/Gas_Springs_22.asp.

BTW the strut as shown is upside down. The body of the strut should be on top because it contains oil that provides lubrication and damping, and to be effective the strut body needs to sit above the strut shaft.
 
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Seymour Snerd

Lifetime Supporter
Got the gas springs/struts installed on the rear clip, but think I ordered them with way too much pressure. Ordered two 125 lb struts.
Mark --

I just called AVM and found out the struts I have are rated at 77 lb, so the ones you have are about 2X too strong. FWIW AVM told me mine are sold to Autozone for a Honda CRX 89-91 if you want to try to buy them that way.

However, based on what I saw at Superformance I suspect we could really use something more like 30-50 lb, and then move the lower mount forward.
 
I have a kit for my MKI from Olthoff but the instructions aren't very good. I was hoping one of you with a MKI and know you have the Olthoff kit installed would share some pictures of your install. I got the same "4684" sticker on my struts and they are 21 1/4"ish center to center. The Honda struts on the AutoZone don't show the length or the holding power and so far the pictures I've seen have an eye at one end so they can't be the same ones. A real part number would be handy.
 

Markus

SPRF40
Lifetime Supporter
Hello Richard,

I have the kit from Olthoff installed by Olthoff - but no pictures available on file....
If nobody is posting anything I can take some pics tomorrow / latest on the weekend.
Do you also need measurements?

Markus
 
Mark, not that I have ever seen. There are large catalogs filled with these things in every size and shape imaginable. If you had onboard air you might be able to use an air cylinder. Push a button and you're up, push another and you're down, well you know what I mean. Speaking of air cylinders I've given real thought about putting an airlift systems on my car. Hiding a floor jack in the 40 is tough. I think I remember seeing them used on Cobra's but never on GT-40s but I've been wrong before, maybe.
 

Markus

SPRF40
Lifetime Supporter
Here we go....
20211125_204157.jpg
20211125_204247.jpg20211125_204224.jpg

My struts also need replacement.... right now (with the worn struts) the rear clip barely does not stay open.... you might try to optimise the position slightly so that gravity keeps the rear clip open if this is possible....

Hope this helps...
Markus
 
Thanks, Markus you're the man. Are you just going to order a replacement set from Olthoff or source them locally? All the ones I've seen are made by AVM Industries. My kit came with the gas struts still in the plastic sleeve with the AVM logo on them. Sorry to say the part number is missing. I don't blame Olthoff it's how he makes a living. AVM has some great info on how to design their struts into your project. Two things they stress are to mount them with the big end up and to limit the stroke so it stops short of full length. I guess the second part could be done with a limiting cable of some sort. Thanks again for the pictures they will really help. Now let me see how many mm are there to the inch?o_O We Americans are so confused. By the way, a friend sold his SPF GT-40 to a guy in Germany a few years ago. Bright red, white strips with the number 40. Do you know who this is? Does he still have the car?
Jacks GT40.JPG
 

Markus

SPRF40
Lifetime Supporter
Richard,
the struts (also with "4684" sticker) just went sour this season - I try to source a replacement here in Germany to prevent the trouble with postage, tax, etc.......
Regarding the red 40 - yes I realized that this car came to Germany but never heard or saw it again..... i think to remember it went into the region of Black Forest....

Talking about metric system :cool:
 
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