C4 Rear Suspension
12-05-2006, 02:31 PM
#1
Rennlist Member
Thread Starter
C4 Rear Suspension
I was reading over on another forum about C4 vs C4S's. They mention that 1995 C4's need a rear suspension upgrade. I did a search here don't find anything that appears to deal with this topic.
Can someone fill me in on this issue? I am looking seriously at '95 C4 and want to know what to look for during a PPI.
Thanks!
Can someone fill me in on this issue? I am looking seriously at '95 C4 and want to know what to look for during a PPI.
Thanks!
12-05-2006, 03:12 PM
#2
Weathergirl
Rennlist Member
Rennlist Member
There's one guy with PCA who says '95s need a complete suspension swap or they're dangerous. He posts this on various forums. The rest of the world doesn't seem to agree. There was never any recall, just an in-line change by Porsche that's fully backward compatible. Apparently, no one has ever put old vs new parts side by side, found a difference, and shared that knowledge with the public.
12-05-2006, 03:23 PM
#4
Weathergirl
Rennlist Member
Rennlist Member
Apparently all '95s, not just C4s. Here's the quote, since I can't figure out how to link directly...
Changing to the later style rear suspension control arms is an absolute necessity for a track, and is close to that on a street driven car. If you have ever felt the back end of the car start fighting back & forth, for example in a bump in a corner, then you are ready for the update.
The update consists of changing the camber arms, kinematic arms, and lower A-arms. The subframe upper arches were revised as well, however, a) they do not affect the suspension geometry, and b) it is virtually impossible to replace them with the engine in the car. Porsche says in fact not to do it. I've done it, and it takes some long hours of trial & error, and it is very very difficult to get it to fit nicely.
I don't know of a technical bulletin on this, all I have found is a statement that they made "suspension geometry changes". The following rear suspension parts were revised for 1996:
1- 993.331.041.02 A-arm L
1- 993.331.042.02 A-arm R
2- 993.331.045.03 Kinematic link L&R
2- 993.331.047.03 Camber link L&R
2- 993.331.131.06 Subframe arch L&R
The toe link was unchanged.
I would not change the arches unless the engine is out of the car.
A rear wheel alignment is required after changing these parts, and the rear toe specification was reduced from 15' per wheel to 10' per wheel as part of this modification.
I just did another one of these the other day, and noted that the rear toe was way way off after the change, like 70 minutes total toe out, which proves the geometry is in fact altered. After setting the camber and correcting (increasing) the toe to spec you are good to go.
Joel Reiser- Website 12/01 revised 11/2005
Joel Reiser - PCA WebSite - 11/21/2005
The update consists of changing the camber arms, kinematic arms, and lower A-arms. The subframe upper arches were revised as well, however, a) they do not affect the suspension geometry, and b) it is virtually impossible to replace them with the engine in the car. Porsche says in fact not to do it. I've done it, and it takes some long hours of trial & error, and it is very very difficult to get it to fit nicely.
I don't know of a technical bulletin on this, all I have found is a statement that they made "suspension geometry changes". The following rear suspension parts were revised for 1996:
1- 993.331.041.02 A-arm L
1- 993.331.042.02 A-arm R
2- 993.331.045.03 Kinematic link L&R
2- 993.331.047.03 Camber link L&R
2- 993.331.131.06 Subframe arch L&R
The toe link was unchanged.
I would not change the arches unless the engine is out of the car.
A rear wheel alignment is required after changing these parts, and the rear toe specification was reduced from 15' per wheel to 10' per wheel as part of this modification.
I just did another one of these the other day, and noted that the rear toe was way way off after the change, like 70 minutes total toe out, which proves the geometry is in fact altered. After setting the camber and correcting (increasing) the toe to spec you are good to go.
Joel Reiser- Website 12/01 revised 11/2005
Joel Reiser - PCA WebSite - 11/21/2005
12-05-2006, 03:28 PM
#6
Rennlist Member
Courtesy of the PCA tech forum:
Changing to the later style rear suspension control arms is an absolute necessity for a track, and is close to that on a street driven car. If you have ever felt the back end of the car start fighting back & forth, for example in a bump in a corner, then you are ready for the update.
The update consists of changing the camber arms, kinematic arms, and lower A-arms. The subframe upper arches were revised as well, however, a) they do not affect the suspension geometry, and b) it is virtually impossible to replace them with the engine in the car. Porsche says in fact not to do it. I've done it, and it takes some long hours of trial & error, and it is very very difficult to get it to fit nicely.
I don't know of a technical bulletin on this, all I have found is a statement that they made "suspension geometry changes". The following rear suspension parts were revised for 1996:
1- 993.331.041.02 A-arm L
1- 993.331.042.02 A-arm R
2- 993.331.045.03 Kinematic link L&R
2- 993.331.047.03 Camber link L&R
2- 993.331.131.06 Subframe arch L&R
http://www.pca.org/tech/tech_qa_question.asp?id={29F9665C-EF0E-4B7B-B6BF-F3356E327CC8}
Changing to the later style rear suspension control arms is an absolute necessity for a track, and is close to that on a street driven car. If you have ever felt the back end of the car start fighting back & forth, for example in a bump in a corner, then you are ready for the update.
The update consists of changing the camber arms, kinematic arms, and lower A-arms. The subframe upper arches were revised as well, however, a) they do not affect the suspension geometry, and b) it is virtually impossible to replace them with the engine in the car. Porsche says in fact not to do it. I've done it, and it takes some long hours of trial & error, and it is very very difficult to get it to fit nicely.
I don't know of a technical bulletin on this, all I have found is a statement that they made "suspension geometry changes". The following rear suspension parts were revised for 1996:
1- 993.331.041.02 A-arm L
1- 993.331.042.02 A-arm R
2- 993.331.045.03 Kinematic link L&R
2- 993.331.047.03 Camber link L&R
2- 993.331.131.06 Subframe arch L&R
http://www.pca.org/tech/tech_qa_question.asp?id={29F9665C-EF0E-4B7B-B6BF-F3356E327CC8}
12-05-2006, 05:43 PM
#7
Rennlist Member
Like RallyJon says, nobody (including Joel Riser) knows exactly what changed in 1996, just that there was probably some type of geometry changes. Yet Riser keeps spouting off about the necessity of spending $2k+ to update, despite having no clear basis. Nobody else but him recommends this. Meanwhile, all us 1995 owners happily drive our unchanged suspension, and many people race with them. It seems to be a non-issue really.
And for him to say that it's "an absolute necessity for the track" is just laughable. He's out of touch with reality.
And it's not a C4 issue, it's a 1995 versus 1996+ issue.
And for him to say that it's "an absolute necessity for the track" is just laughable. He's out of touch with reality.
And it's not a C4 issue, it's a 1995 versus 1996+ issue.
