C5 Rear Subframe

cachaciero · Post by **cachaciero** » 02 Jun 2009, 22:05

While researching the subject of rear suspension mods I came across a procedure for aligning the rear subframe front mounts which it would appear could be fitted incorrectly if one was unaware that they have to be aligned in a certain way.

I have to say that this was not very clear to me as to the whys and where fores anybody know anything about this? and particularly what happens if they are fitted incorrectly?

Cachaciero

AndersDK · Post by **AndersDK** » 03 Jun 2009, 19:52

The usual precautions not to torque bolts until normal load is applied to the rear subframe and all parts ?

Thats what you normally do to subframes, suspension arms, bushings, arb's etc.

cachaciero · Post by **cachaciero** » 03 Jun 2009, 22:33

Hi Anders

No it's more complicated than that hence the question, the bushes or maybe they could more correctly be called dampers (depends on RPO number) appear to either have a specific radial orientation or maybe they are " wound up" radially, it's not clear quite what the Citroen special tool for this job does but the settings are different Left and right.

Cachaciero

AndersDK · Post by **AndersDK** » 05 Jun 2009, 18:55

The torque dampers ?

They are there to minimize suspension excursions on the subframe - in that direction they are fitted. One of the secrets in the C5 sublime suspension.
They need to be balanced eqaul side to side on the subframe.

I believe you will need a Citroen workshop procedure to do it correctly, unless you can see if its sort of self explanatory when viewed from underneath.

cachaciero · Post by **cachaciero** » 06 Jun 2009, 10:59

AndersDK wrote:The torque dampers ?

They are there to minimize suspension excursions on the subframe - in that direction they are fitted. One of the secrets in the C5 sublime suspension.
They need to be balanced eqaul side to side on the subframe.

I believe you will need a Citroen workshop procedure to do it correctly, unless you can see if its sort of self explanatory when viewed from underneath.

Hi Anders

I have what I believe to be the relevant parts of the C5 workshop procedure and it's still not clear !.. I suppose if you are refitting the subframe AND you have all the Citroen special tools and you only have the mental agility to do things by numbers then I guess it's adequate.
BUT if like me you wan't to understand a bit about how it's supposed to work so that one can make some assessment of what happens if it's not put back together correctly AND work out how to put it back correctly WITHOUT the Citroen Toolbox then the Citroen workshop procedure is somewhat inadequate.

In the end my problem is this, I have a car which has a steering bias to the left, having spent sometime with the front end I can find nothing obviously wrong on the front suspension / steering. So I am now turning my attention to the rear end, now given that the whole subframe is mounted on rubber this doesn't give me the highest confidence that it will stay in alignment for life. Further early C5's were notorious for rear axle problems which were kind of fixed with successive "bodges" from the factory one of which included changes to the front mountings. Now on my car such history as I have would indicate that this problem of left bias stated occurring around about 50 /60 K miles unfortunately this history is not complete it doesn't show me when this car had the rear axle mods done, Citroens own records of the car only says that they have been done.
So a mental question I have is did this problem start to occur after work was done on the rear axle?
To answer that I have to understand whether it is theoretically possible for the mountings which are on the face of it just cylinders of rubber to be fitted in such a way that the subframe can be canted / offset from the centre line, bearing in mind it would not take much, probably only a couple of millimeters to produce a steering bias one way or the other. It is possible that the mounts have different degrees of compliance depending on orientation I suspect that they have BUT I don't know, it this kind of information I am seeking.

Cachaciero