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RS Top Mounts with Bilstein PSS10

 
Old 04-27-2013, 12:25 PM
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ToSi
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Default RS Top Mounts with Bilstein PSS10

Original 993RS top mounts have a few advantages over the various aftermarket parts. Posts below show how to install them with Bilstein PSS9 or PSS10 shocks, use at your peril

Front, #2 shoulder bolt is machined from steel, M14x1.5 shoulder nut that's been zinc chromate coated. It is required since the threaded portion of the Bilstein shock does not extend beyond the upper surface of the monoball:


Small Parts:
order here, 9 -> 6 -> 7 on 8 -> 2



Bilstein PSS10, 993RS Top mount, + above


Assembly order:


Note protruding shoulder:


M14 Hardened washer (inc w/ PSS), note ~2mm clearance to top of shock hat. (Spacer #6 used to hold washer in place, ignore):


Spring preload pushes hat against washer. This is intentional by Bilstein & allows the hat to rotate, avoiding binding and noise. Occurs regardless of top mount used.


Top mount assembly-
Lower spacer:


Seal:


Slide over shock:


#2 Shoulder Bolt functions as upper spacer + nut, dab of blue loctite on threads:


Note clearance during full articulation, close but no contact.


Install top cap, ready to go:




Shoulder Bolt Details - measurements are 'reference only', I'm using Harbor Freight calipers which have been dropped a couple of times.. close enough to get the idea across but anyone making a set will want to take the top mounts to your local machinist for a real measurement of the monoball ID.

Shoulder Nuts - M14x1.5 thread.










CRITICALLY IMPORTANT! Slip fit to monoball.





Last edited by ToSi; 05-04-2013 at 09:26 AM.
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Old 04-27-2013, 12:26 PM
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Rears can be assembled from various off-the-shelf parts (Porsche OE Mounts, Rennline Top Hats):


Note, a thin M12 washer used in position #8 to distribute load across a larger contact area between the aluminum top hat & the steel monoball spacer. The 8mm thick washer provided by Bilstein is not used.

The entire assembly to locates the top of the shock in the same position as the original non-RS mount - ~38mm below the body. This is important to maximize travel while limiting upward suspension / wheel motion.

Parts:


Trail fit (note, M12 hardened washer not installed in this photo):



Last edited by ToSi; 04-27-2013 at 01:13 PM.
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Old 04-27-2013, 12:55 PM
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Note the amount of core shift in the caps - not sure if this is sloppy casting or just the result of 20+ yr old tooling. Looks too close for comfort:





Cleaned-up, no chance of contacting the monoball now.


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Old 04-27-2013, 04:53 PM
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Thanks for posting!
So if I understand, the shoulder bolt is used to compensate for the lack of spindle length when using the large spacer?
With the rennline fronts the spacer is smaller, so the standard nut can be used, but I wonder if it will still allow for interference with the bottom lip on the mount...
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Old 04-27-2013, 05:09 PM
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yes, called it a shoulder bolt - 'shoulder nut' is probably more appropriate. The RS shocks have a longer threaded portion. The custom nut accomplishes the same.

The key to avoiding issues is to keep the spring seat & shock in the same relative locations vs. the underside of the mount.

From photos, it looks like the Rennline mounts use smaller / thinner monoballs - this might allow enough of the shock thread to protrude for a normal locknut but you'll want to check clearances before installing!
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Old 04-27-2013, 05:46 PM
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Fantastic information thanks!
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Old 04-28-2013, 11:44 PM
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For the fronts, do you know the thickness of the spacer that sits between mount and hat?
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Old 04-29-2013, 04:42 PM
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Nice write up
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Old 04-29-2013, 04:55 PM
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Default What camera are you using?

Tosi,

Very nice pictures! Great exposure and detail. I need to look at getting another
camera. What are you using?

-bruce
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Old 04-30-2013, 12:11 AM
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Thanks guys, updated post #1 w/ details for the spacers & nuts.

Bruce, believe it or not, all photos were taken w/ my phone (Samsung Note II)!
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Old 04-30-2013, 10:43 AM
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FYI -- I found out yesterday that Rennline also makes the shoulder nuts.
Also, while the PSS9 has the protuding shoulder on the front shocks, as this appears to be part of the design with the spring hats I'm not sure it requires the beveled washer/spacer.

Last edited by dgmattingley; 04-30-2013 at 11:44 PM.
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Old 05-02-2013, 02:41 PM
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il pirata
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Originally Posted by dgmattingley View Post
FYI -- I found out yesterday that Rennline also makes the shoulder nuts.
Also, while the PSS9 has the protuding shoulder on the front shocks, as this appears to be part of the design with the spring hats I'm not sure it requires the beveled washer/spacer.
After talking with Tom at Rennline, their "shoulder nut" will not work if you are using RS mounts (versus Rennline mounts). Tom is checking to see if they have an interest in making a shoulder nut that works with the RS mount/Bilstein setup. If not we are talking locally with a shop...would be nice to get someone who has a CNC machine to set it up once.

Also I think ToSi will be updating info that the custom beveled spacer is not required after talking with Bilstein...instead just use the hardened M14 fender washer included w/ the shocks.
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Old 05-04-2013, 09:25 AM
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Updated w/ latest info.

PM me if you want a set of these, would consider having a batch made if enough interest.
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Old 05-04-2013, 11:59 AM
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What doesn't make sense here is the answer to the question: Why doesn't Bilstein make a strut with a longer top stud for the Carrera RS so all this custom hardware is unnecessary??

They make no strut to fit a 964/993 Carrera RS and the market would seem to be there to support it.

Not to mention that the original RS Bilstein is the sealed, un-rebuildable twin tube style, not the more trick upside down monotube style like the PSS9/10 - one would think a lot of RS owners out there would be itching to upgrade.
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Old 05-04-2013, 01:58 PM
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[QUOTE=ToSi;10436174]Updated w/ latest info.

PM me if you want a set of these, would consider having a batch made if enough interest.
[/QUOT

I am confused now. I thought we only needed a custom shoulder nut in the front for each side. What are the three parts in the picture?
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