JasonAndreas

Thanks Roland!
I've been wanting to put on the Carrera RS shocks and springs but not with monoballs, I will go this route instead.

Laurence Gibbs

Just a bit confused. Bilstein say you can't re-valve genuine RS struts, which are a twin tube design. I am assuming then that your struts are single tube design? And therefore will never match RS spec?

Cupcar

Are the HD shocks "reversed double cylinder" (my term) like the Cup and RSR shocks Porsche uses?

Normally the strut rod attaches at the chassis and the piston moves up and down in the strut cylinder.

In the "reverse double cylinder" construction type the piston rod actually is attached at the bottom of the strut and moves in a cylinder attached at the chassis with the strut itself sliding over the additional cylinder. This makes the design much stiffer and presumably this is why Porsche uses them in their racing models.

They look like this Bilstein made for H&R:

Cupcar

BTW the Euro RS struts are not a twin tube design, only the Cup and RSR. See photo below of one:

chancecasey

That's got to be the most erotic strut pic I've seen in a while...

Laurence Gibbs

Interesting that. As Bilsteins own web site states they ARE a twin tube design. I would suggest you look at www.bilstein.de for a definition of twin tube gas shock absorber. Porsche's own service information Tecknic for the 964RS (wkd 497 620) also says they are twin tube. And just about every book I have read on the subject says they are twin tube. Maybe you are confusing the technologies. A twin tube shock has an orifice at the bottom of the shock body that the gas or oil flows through to the outer second tube. See the website for a more accurate defintion! It has nothing to do with the way the top of the shock body is sealed to the rod.

Cupcar

I understand the difference between "Twin Tube" and "Single Tube" shocks, that is why I used the word "cylinder" instead of "tube" in my description. I am not enough of a wordsmith to describe the differences I see in the designs.

Twin Tube shocks compensate for the volume displacement of the piston rod as it enters the oil chamber by moving oil though a foot valve to the second tube while a single tube design has a floating piston separating the oil chamber from a high pressure gas filled chamber and the volume displacement by the piston rod moves this floating piston to compensate.

I actually thought both the shocks, racing and Euro RS, I pictured above are of the single tube design, but with the components inverted as the difference. Perhaps the Euro RS shock is a Twin Tube and the H&R/RSR/Cup is a Single Tube design.

Pictured below is a Carrera Cup factory shock to show a factory part with the larger diameter cylinder for a strut rod.it is 40 mm in diameter the Euro RS is only 22 mm in diameter.

Cupcar

I just checked and you are absolutely correct, on page 4-2 of the Euro RS book it says the front strut is a twin tube design and on page 4-5 it states the rear shocks are of a single tube design.

So it looks like the front struts with a 22 mm solid rod are of the twin tube type and the racing type with the 40 mm hollow cylinder are of the single tube type, with the tube itself being the strut rod.

So my question is what type are the Bilstein HD, 22 mm or 40 mm?

Roland 93

When I had my VE3-5277/5278 (late model HDs) revalved, the techs at Bilstein in San Diego confirmed it was a mono-tube insert installed inverted in the strut. (like RSR struts?). The earlier model HDs, F4-V36-0385/0386, were double-tube like the RS units.

One of the techs said they did not revalve double-tube shocks, like the Euro RS units.

Euro RS struts also have a longer threaded top rod section which requires the RS monoball perch and are too long for stock steel/rubber perches. The HDs work with the stock perches but may be too short for the RS perches. Of note, the HDs can be used with aftermarket monoball/camber plates as most of them incorporate different height spacers to accomodate both types of Bilsteins. I don't know if this is true for the stock RS perches.

Laurence, you are correct. My front struts will never truly match the Euro RS unit. They are effectively an RS "valved" Bilstein that are mono-tube, revalveable, fit the stock steel/rubber perches (aftermarket monoballs too), and worked out to be the best overall choice for me.

Cheers
Roland

Cupcar

I think the Bilstein HD units with the Single Tube are probably the best for track use given that Porsche uses them in their racing cars.

The RS monoball mount does not have provision for anything but mounting to an RS shock unit as far as I can tell, see gold spacers below in photo.

I bet Bilstein has monotube rebuild inserts with a long enough stud to mount into an RS monoball.

Euro RS front Monoball mount and spacers below (Bill Gregory photo)

Laurence Gibbs

The euro RS monoball's will mount to KW's struts and probably to others. I think from a cost perspective the single tube designs make a lot of sense, as they can be rebuilt. The Euro RS struts cannot be rebuilt and they are expensive to replace. I am most interested in your Carrera cup spring picture I have seen quite a few differing pictures of these (see www.fvd.de catologue for some more) Some appear progressive and some not do you know any more about what was fitted to what? and which springs used the "colors" for fittment.

Cupcar

Here are pictures of the 964 Carrera Cup entire suspension kit I have, less rear mounts. The springs have no "color" markings, they are marked Carrera 2 HA Cup and Carrara 2 VA Cup for rear and front axel respectively (H=Hinten and V=Vorn). The rates are progressive 200-600 front and 240-800 rear I am told (I suspect the true working rates to be 600/800 when at ride height.

Laurence Gibbs

Sorry spelling mistake ! should have read collars not colors or colours. I was refering to the collars that are on the cup springs in the FVD catalogue.

Laurence Gibbs

i have been doing a bit more research on the cup suspension. It would seem(reading between the lines) that there are two types of "cup" suspension. one built for road approved "Cup's" (clubsport and NGT? ?) and one for the race car. I believe the linear spring versions are for the race car and the progressive versions are for road approved "cup" cars. I would guess this originally allowed the Carrera cup teams to swap out suspensions for a wide range of tracks from Nordschliefe (almost a road circuit) to Spa which is billiard smooth (almost!)

Cupcar

I see you meant "collars", I thought you meant the stripes of color used on the springs to indicate the chassis specification the spring is for.

The 964 RS was built in 4 versions the 1) "Carrera RS Base or N/GT", 2) "Carrera Cup" option M001, 3) " Carrera RS Touring" option M002 and "Carrera RS Clubsport" option M003.

The Carrera Cup parts book only lists the springs and shocks shown in the picture above, no optional springs are listed. This car is not street legal.

The Base N/GT, Touring and Clubsport all came with the same spring and shock set and these cars were street legal.

This is the way I understand things anyway.