1969 2800CS strut dilemma - Bilstein's won't fit!

[Dave G]

I went to install new front Bilstein shocks in the front struts and they didn't fit. They are Bilstein PN 34-000243 which is the only B6 shock that the Bilstein catalog shows to fit a 1969 2800CS (Euro delivery 01/69). So now I am wondering if my struts are stock or from another model or if the Bilstein shock compatibility chart is not accurate. Without OE dimensions or drawings I’m at a loss for how to proceed. Photos and measurements of the offending parts are provided below and I’m hoping the knowledge of the Forum can help determine the answer to this mystery! The most relevant dimensions from below are, 1) Strut tube is 429 mm deep, on the inside (16 ⅞”), 2) Strut base to perch bottom weld is 368 mm, see photo below, 3) Strut tube outer diameter is 52.2 mm (has the M50x1.5 internal threads to engage the gland nut)

I found several good discussions on struts, links below, but I wasn't able to resolve my issue from them...
E24 strut use (The E24 struts appear to be flared out at the top where the gland nut engages, NOT like my struts)
E3's and 3 strut types
CSL strut tubes (definitely not the same as my struts)

Thanks in advance for your help - Dave

Bilstein Catalog, https://workshop.bilstein.com/wp-content/uploads/2021/03/BILSTEIN_Program-2020_EN.pdf

1. The Bilstein vs Boge front shocks

2. Strut tube is 429 mm deep (16 ⅞”)

3. Front stub axle is about 5 degrees below perpendicular in the photo below

4. No room to thread on the gland nut below!

5. The old shock has a recess for the gland nut to thread on but new one doesn't

6. Old Boge shock PN 1-0201-32-140-0 (1020 1321 400) and/or 1 112 210 2 (1112 2102)

7. The two old Boge shocks are slightly different models but same size overall

8. Old shock PN’s didn't match, but both fit

9. Strut base to perch bottom weld is 368 mm

10. Strut outer diameter is 52.2 mm

 

[Stevehose]

Is there a 3 digit number cast into the bottom area where the wheel bearings mount?

 

[Thomas76]

I just installed those shocks and struggled to get them all the way down. Tolerance is tight therefore anything foreign inside will seize the shock before it is in place. Is it possible your shock is not in bottom yet?

 

[Fritzie]

Hello,
On the german site same discussion. I have translated it (google )

“Suspension struts of 2800 CS have 3x M8 threads at the bottom. Shock absorber tube is slightly smaller in terms of diameter. Shock absorbers from "Bilstein" do not fit.

Struts of 3.0 CS CSI have 3x M10 threads at the bottom. Shock absorber tube is slightly larger in terms of diameter. Shock absorbers from "Bilstein" fit.

This is my level of knowledge...”
=====

And one of the replies gives the following information;

=====

“Hello

So that with the pipe diameter M48 or M50 is not quite right. The spring strut of the 3 liters with M10 thread at the bottom was available with both tubes. I have both new in stock, with the same part number, once M48, once M50.

I can't say with certainty whether the 2.8 spring strut always had the M48 tube. But if it's important, I like to check, I also have a few new ones.”

=====

Maybe it’s helpful for your situation

 

[Fritzie]

I went to install new front Bilstein shocks in the front struts and they didn't fit. They are Bilstein PN 34-000243 which is the only B6 shock that the Bilstein catalog shows to fit a 1969 2800CS (Euro delivery 01/69). So now I am wondering if my struts are stock or from another model or if the Bilstein shock compatibility chart is not accurate. Without OE dimensions or drawings I’m at a loss for how to proceed. Photos and measurements of the offending parts are provided below and I’m hoping the knowledge of the Forum can help determine the answer to this mystery! The most relevant dimensions from below are, 1) Strut tube is 429 mm deep, on the inside (16 ⅞”), 2) Strut base to perch bottom weld is 368 mm, see photo below, 3) Strut tube outer diameter is 52.2 mm (has the M50x1.5 internal threads to engage the gland nut)

I found several good discussions on struts, links below, but I wasn't able to resolve my issue from them...
E24 strut use (The E24 struts appear to be flared out at the top where the gland nut engages, NOT like my struts)
E3's and 3 strut types
CSL strut tubes (definitely not the same as my struts)

Thanks in advance for your help - Dave

Bilstein Catalog, https://workshop.bilstein.com/wp-content/uploads/2021/03/BILSTEIN_Program-2020_EN.pdf

The Bilstein vs Boge front shocks

Strut tube is 429 mm deep (16 ⅞”)

Front stub axle is about 5 degrees below perpendicular in the photo below

No room to thread on the gland nut below!

The old shock has a recess for the gland nut to thread on but new one doesn't

Old Boge shock PN’s 1-0201-32-140-0 (1020 1321 400) and/or 1 112 210 2 (1112 2102)

Old shock PN’s didn't match, but both fit

Strut base to perch bottom weld is 368 mm

Strut outer diameter is 52.2 mm

I have measured my 3.0 csi struts; same outer dimension 52.2 mm

 

[merdad]

On my 2800, they fit in perfectly,

 

[bavbob]

I do recall looking at my set-up when I was doing this and thought for sure there would not be enough room between the housing and strut to fit the gland nut, but it did.

So dumb question, did you try to slide the gland nut all the way down and see if it would thread? It goes over the strut, it does not rest on top of it.

 

[Dave G]

Is there a 3 digit number cast into the bottom area where the wheel bearings mount?

853.1 L, 854.1 R

 

[Stevehose]

Check this post out:

https://e9coupe.com/forum/threads/front-struts.40976/

I had mismatched struts and mine had these numbers:

385 01 (Correct for my car)
386 198D R (Incorrect-from a later model)

I would research more into seeing if you have the very early strut - perhaps the casting number will help.

 

[Dave G]

I do recall looking at my set-up when I was doing this and thought for sure there would not be enough room between the housing and strut to fit the gland nut, but it did.

So dumb question, did you try to slide the gland nut all the way down and see if it would thread? It goes over the strut, it does not rest on top of it.

I did try, but I may try again just to be sure - thanks

 

[Dave G]

I just installed those shocks and struggled to get them all the way down. Tolerance is tight therefore anything foreign inside will seize the shock before it is in place. Is it possible your shock is not in bottom yet?

It was a close fit but the measurements seemed to confirm the shock was inserted fully. The strut tube was 429mm deep at the center of the hole and less at the walls due to a concave bottom and/or weldments - hard to see. The shock body was 425mm long and it fit fully in but left no room to engage the the gland nut. I'll try again to be sure I'm not missing something

 

[Breiti]

Have your try to slip the nut over the shock housing when not installed?

I assuming, the thread from there nut fit in the strut tube?

If both work, first slip the nut over the shock, then stuck it in the strut tube.

Breiti

 

[Dave G]

@Fritzie - thanks for the information from Germany, very interesting about the 48 and 50 mm strut tubes being used on 3.0CS cars. Yes, mine is a 50 mm ID, however I'm unsure what depth the 50 mm tubes should be. Mine is 429 mm max. Hopefully someone has a spare strut around that they could measure the internal tube depth and report back!

 

[Dave G]

@Breiti - Yes the new and old gland nuts fit without the shock installed. I think I tried what you are saying about slipping the nut over the shock and then sticking them in the tube but the shock takes the space where the nut needs to go. See the 4th photo above

 

[Henrik]

I had exactly the same problem when I bought Bilsteinś for my 2800CS. There are nothing wrong with your struts, they just have a different dimension. I tried to make the bottom end of the Bilsteinś a bit "egg" shaped with a grinder (not recommended!!) But it did not help. In the end I solved it by buying used struts from a 3.0.

 

[Fritzie]

@Fritzie - thanks for the information from Germany, very interesting about the 48 and 50 mm strut tubes being used on 3.0CS cars. Yes, mine is a 50 mm ID, however I'm unsure what depth the 50 mm tubes should be. Mine is 429 mm max. Hopefully someone has a spare strut around that they could measure the internal tube depth and report

@Fritzie - thanks for the information from Germany, very interesting about the 48 and 50 mm strut tubes being used on 3.0CS cars. Yes, mine is a 50 mm ID, however I'm unsure what depth the 50 mm tubes should be. Mine is 429 mm max. Hopefully someone has a spare strut around that they could measure the internal tube depth and report back!

Hello,
I checked 5 tubes: all different numbers on the foot ( of coarse left is different from right) . See photos.
But: all 50 mm strut, all same diameter outside 52,2 mm and all the same length

The ones on my car 3.0 cs 1972 are equal

 

[Hans woonboot]

Hallo,
Ik heb 5 buizen gecontroleerd: allemaal verschillende nummers op de voet (van grof links is verschillend van rechts). Zie foto's.
Maar allemaal 50 mm veerpoten, allemaal met een diameter buiten 52,2 mm en allemaal dezelfde lengte

Die op mijn auto 3.0 cs 1972 zijn gelijk

 

[Hans woonboot]

Hallo Dave, hier zijn een paar foto's van de veerpoot van mijn 2800 jaar 68. gr Hans

 

[Dave G]

Problem resolved! The front Bilstein shocks did fit after all! Upon trying again a bit more carefully and thoroughly, the Bilstein gland nut on the new shocks is designed to be thinner and fit down the space between the shock outer diameter and the internal threads. Thanks everyone for your input to help resolve this, especially those of you measured your struts for me to compare and @bavbob , @Thomas76 , and @Breiti for encouraging me to try harder!

 

[Fritzie]

Problem resolved! The front Bilstein shocks did fit after all! Upon trying again a bit more carefully and thoroughly, the Bilstein gland nut on the new shocks is designed to be thinner and fit down the space between the shock outer diameter and the internal threads. Thanks everyone for your input to help resolve this, especially those of you measured your struts for me to compare and @bavbob , @Thomas76 , and @Breiti for encouraging me to try harder!
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And a happy new year!!