RAASpeedster

I have a 94 C4 Widebody coupe and just got some input from Bilstein about which one to use. Here's the response.

​​​​​​Below is a link to your vehicle in our online catalog and all of the products we design test and tune for your application. Unless your vehicle is an RS version from Europe, you will want to use the standard kit. These vehicles take different strut mounts and therefore the stems on the each damper are different. These kits are not interchangeable between the different chassis. You can purchase our products through distributors like FCP Euro, Summit Racing or Tire Rack to name a few. Thank you.

Seems the standard will be what I get. Probably will change a lot of bushings as well

jeff33702

So if you're OK upgrading to RS top mounts, then the PSS10 RS version will fit fine, is what I'm getting from this.

-nick

Exactly, RS front top mounts are all that’s required for hardware. Using all factory parts should be plug & play. Aftermarket top mounts always require adjusting the spacer stack under the monoball. You’ll need to run near RS height to keep the shorter strut relatively centered in its travel as well. It will ride a little more harshly- less front travel available, and RS kits typically spec a stiffer rear spring.

Standard caveats for early rear shock top mounts apply, same as the non-RS parts.

jeff33702

It's amazing that so many vendors have this messed up. Rennline says RS AMerica is good to go...but we know that is not the case.

Rennline:



Tire Rack:

mby

Please don't forget that the rear construction was significantly changed at the end of 1990 (see for example p. 21ff. of https://shop.bilstein.com/files/Guta...M4-Y591A00.pdf or in Porsche's parts catalog).

jeff33702

I think the OP ended selling his RS versions... I'm kinda interested in a new set, the price is right... but that price seems like it could be very offset by the high price of obtaining RS top mounts.

So what's the loved setup lately?

I could go 3 ways

1 - PSS10 RS kit, RS monoball top mounts $$ (if there's a less expensive way to get RS spec top mounts from 3rd party, I could like this)
2 - PSS10 Standard kit, 3rd party monoball top mounts
3 - PSS10 Standard Kit, OEM 964 rubber mounts (new). I know there's some flex in the rubber but seems like there would be a good NVH reduction as well vs monoball.

For reference - here is the diagram of RS vs Non RS.

jeff33702

Figured I'd bump this. I'll add the install to my project RSA thread when I get to the actual install but wanted to say - I did buy the RS version of the PSS10 and, if you are going with monoball front/rear top mounts, these seem to be the ones you want. A lot of older threads, I think, before these were available documented how to install the non-RS PSS10s with monoball top mounts (because they were not meant for that, they are supposed to bolt onto stock rubber tops). Using the original non-RS PSS10 required you to buy a specific spring hat for the rear from Rennline - this RS kit, comes with a correct hat that fits the spring and is meant to use with monoball top mounts. In addition to that, it seems like these might prevent the situation many people complain about, which is that monoball tops would raise your car...requiring that you wind down the spring perch, ultimately resulting in almost slack helper springs at RS ride height.

The differences in the rear spring hats are well documented here:
Jackals racetrack (jackals-forge.com)
He machined his own hat but you can either buy them from rennline or you can get the RS kit to begin with. The kicker is that the RS kit cost less

I'm curious how this all plays out in actual use - the spring rate is slightly different on these as well.