History qn: When did Porsche 911 Rear Control Arm Pivot Boxes first appear?

[obrut]

Trying to determine the year when Rear Control Arm Pivot Boxes (see pic) started being used?

Did 3.0RSR's have them? 934? 935?

[andrew15]

It's possible that Kremer used them when they used coil overs on the early RSRs
AM

[obrut]

Thanks Andrew, so would this be about 73 or 74?

[winders]

Is this a vintage racing period correctness question?

Scott

[andrew15]

The coilovers were in 73, and it's not out of the question the brothers experimented with the boxes around the same time.

[obrut]

Is this a vintage racing period correctness question?



Scott

Yep

[Flieger]

I always thought those were aftermarket items from maybe the late 80's or early 90's.

[Flieger]

Looks like they go back to the 935. I don't think the RSRs ran in classes that allowed moving the pickup points from their homologated positions.


Porsche 934.5 Brumos Racecar_ 057 by Max_911S_fahrer, on Flickr

[winders]

I don't think the RSR ever had them because you would need to raise the outer pickup points if you were raising the inner pickup points. The 935 ended up with adjustable out and inner pickup points. I am not sure if the 934 had them. But, as you can see from the picture Mac provided, the 934.5 did.

Scott

[TimT]

I looked through some documentation I have, a few out of print books, etc..

It appears Porsche first raised the rear pick ups for the 935/78 when they raised the floor of the car flipped the transmission, there are indications the the 935 baby had modified inner pick ups..


All references prior (RSR) to that mention moving the pick up to the rear to use with fabricated swing arms...

And coil helper spring were available for the rear in Ti for DM 1000

I have been underneath a real 935, and it did not have an adjustable pickup like the one pictured, they just welded some extra material above the original pick-ups and drilled holes where needed

[winders]

Originally Posted by TimT

It appears Porsche first raised the rear pick ups for the 935/78 when the raised the floor flipped the transmission, there are indications the the 935 baby had modified inner pick ups..

The raised pickups were really needed when Porsche started using that 19" rear tire. The car had top be lowered massively to get the cg back down where they wanted it. This, in turn, required raising both the inner and outer pickup points significantly to get the roll center back up where it needed to be and to get the suspension to operate in the correct range under bump and rebound. The transmission was flipped to get the axle angle back to something reasonable.

Originally Posted by TimT

All references prior (RSR) to that mention moving the pick up to the rear to use with fabricated swing arms...

The RSR got a shorter trailing arms that required the inner mount be moved out from center about 25mm and rearward about 48mm. The height wasn't changed though. The 930 received that change but neither car had a raised outer pickup point.

Scott

[Flieger]

I think they may have moved up a few mm's on the 930.

[TimT]

The 930 used the RSR ( racing iterations) pickup points, out and back, according to Boschen-Barth.

Every resource I have available has no mention of raising the height of the pick up points until the cars got lowered extremely flipping the trans etc...77-78

I wonder if what the privateers did compared to the factory matters to a vintage racing org?

[obrut]

Thanks guys, I'm looking into this wrt the potential purchase of a historic race car that has these parts fitted. The car was raced, and upgraded, from the late 70's to the late 80's. I'm trying to work out when this change was made and thus whether or not I would need to remove these parts for a particular class.

[winders]

Originally Posted by Flieger

I think they may have moved up a few mm's on the 930.

As I said, the 930 did receive that change. The inner pickup points were moved up 10mm. The outer pickup points remained stock. Anderson says it was for anti-squat. Others here suggested it was something else which I don't recall.

Scott

[DaddyGlenn]

Perhaps this is a question for Grady?