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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: https://lh4.googleusercontent.com/-v...520Diagram.jpg Small Parts: order here, 9 -> 6 -> 7 on 8 -> 2 https://lh6.googleusercontent.com/-q...ront%2520b.jpg Bilstein PSS10, 993RS Top mount, + above https://lh4.googleusercontent.com/-o...ront%2520a.jpg Assembly order: https://lh3.googleusercontent.com/-W...640/front3.jpg Note protruding shoulder: https://lh5.googleusercontent.com/-w...640/front4.jpg M14 Hardened washer (inc w/ PSS), note ~2mm clearance to top of shock hat. (Spacer #6 used to hold washer in place, ignore): https://lh5.googleusercontent.com/-K...ront%2520e.jpg 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. https://lh4.googleusercontent.com/-3...ront%2520f.jpg Top mount assembly- Lower spacer: https://lh6.googleusercontent.com/-C...640/front7.jpg Seal: https://lh3.googleusercontent.com/-7...640/front8.jpg Slide over shock: https://lh5.googleusercontent.com/-S...ront%2520g.jpg #2 Shoulder Bolt functions as upper spacer + nut, dab of blue loctite on threads: https://lh3.googleusercontent.com/-n...640/front9.jpg Note clearance during full articulation, close but no contact. https://lh5.googleusercontent.com/-f...ront%2520h.jpg Install top cap, ready to go: https://lh4.googleusercontent.com/-t...00/front10.jpg 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. https://lh4.googleusercontent.com/-y.../s640/nut1.jpg https://lh5.googleusercontent.com/-7.../s640/nut2.jpg https://lh5.googleusercontent.com/-X.../s640/nut3.jpg https://lh5.googleusercontent.com/-C.../s640/nut4.jpg https://lh4.googleusercontent.com/-u.../s640/nut5.jpg CRITICALLY IMPORTANT! Slip fit to monoball. https://lh5.googleusercontent.com/-H.../s640/nut6.jpg https://lh6.googleusercontent.com/-L.../s640/nut7.jpg https://lh4.googleusercontent.com/-E.../s640/nut8.jpg |
Rears can be assembled from various off-the-shelf parts (Porsche OE Mounts, Rennline Top Hats):
https://lh5.googleusercontent.com/-A...520Diagram.jpg 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: https://lh3.googleusercontent.com/-Z...%2520parts.jpg Trail fit (note, M12 hardened washer not installed in this photo): https://lh6.googleusercontent.com/-7...s800/rear2.jpg https://lh6.googleusercontent.com/-y...s800/rear3.jpg |
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:
https://lh6.googleusercontent.com/-Y...s800/Caps1.jpg https://lh4.googleusercontent.com/-2...s640/Caps2.jpg Cleaned-up, no chance of contacting the monoball now. https://lh6.googleusercontent.com/-Z...s800/Caps3.jpg https://lh3.googleusercontent.com/-y...s640/Caps4.jpg |
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... |
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! |
Fantastic information thanks!
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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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Nice write up
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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 |
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)! |
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. |
Originally Posted by dgmattingley
(Post 10425234)
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. 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. |
Updated w/ latest info.
PM me if you want a set of these, would consider having a batch made if enough interest. https://lh6.googleusercontent.com/-U...0/IMAG0934.jpg |
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. |
[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. https://lh6.googleusercontent.com/-U...0/IMAG0934.jpg[/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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