2.7 RS rear trailing arm details

[Alan.uk]

Hi, I originally posted this on another thread but also wanted to add it here.

We have been fortunate enough to have had several RSs in for works/restoration recently and I have been meaning to post some of the specific differences in RS shells/mechanics. One of which is the unique steel trailing arms which have additional strengthening. These are the fore farther of the later ally arms. One of the RSs in for restoration had a none matching pair of rear arms, one was an original RS and one was a standard set up.

Original RS compared to standard


close up of an original


These things are not easy to find so instead we made the additional metal support and welded it in as per original RS.



Porsche's welding was never that tidy so I guess our re-creation is not exact :lol:



Thanks

Alan

[chris_seven]

Alan. are these the short arm as fitted to some of the later 2.7RS models?

If so does this mean that they are the same as the RSR?

[manu72S]

Alan

great work

Could you post another pictures about the parts please ?

thx
Manu

[denson]

Are we saying that the RS trailing arms played a serious part in the RS handling?. I am asking as the driver side arm om my rs was bent so I replaced both with later model units. I have both, but need to have one straightened. I will spend the $ to do that if everyone agrees they are an important component to the rs and it's handling.

Thanks,

John

[Neunelfer]

John, I would say so...

I'm thinking of performing this mod to some steel arms and going back to steel. Fence sitting right now.

[chris_seven]

The PET clealry shows two different part numbers for the Carerra RS Rear Trailing Arms and I thought this was due to a change in length.

I believe later 2.7RS used the shorter arm which changed the roll centres and camber change and this geometry was used in the RSR and 3.0RS.

Is just strengthening the main improvement or were the later cars better because of the significantly better geometry.

I have been trying to find a set of the short arms for some time but without any luck

911.331.053.20 and 911.331.053.10 for Left Hand

911.331.054.20 and 911.331.054.10 for Right Hand

Anyone know for certain?

If these later arms were shorter and the same as the RSR Arm it would be good to know.

[Alan.uk]

Hi,

The arms in the pics are standard length arms. Basically these are exactly the same as those used on all 72 and 73 models but with the extra support plates/webs welded in, and to be honest Porsche's welding was never that great. Does any one know what number RS use the shorter RSR style arms? I have had 5 RSs in recently (up to number 14!!) and all had (bar the one for car in the pics above) the standard steel arm with additional support webs. For me personally if I had an RS I would want these arms fitted. Porsche also used a support plate from the chassis to the torsion bar housing, again this was done for strength.

Thanks

Alan

[210bhp]

Shorter arms from 9/5/1973 and chassis number 1409 although there may be some differences around that date as we know cars may not have been built in sequential chassis number order.


Regards
Mike

[Neunelfer]

I believe later 2.7RS used the shorter arm which changed the roll centres and camber change and this geometry was used in the RSR and 3.0RS.

Agree... this mod is detailed in Bruce's book. It allowed the RSR's which were homogulated off the RS chassis to have the later arms. Fairly simple welding trick from what I recall.

[Neunelfer]

Alan, BEAUTIFUL work BTW.