Custom Rear Shock mounting options - any experts out there?

[wjdunham]

I have a need for a not-standard rear shock configuration and want to explore the various options.

Why? I have a 1969 chassis into which I have installed Carrera aluminum trailing arms. The arms have ~1" machined off the shock mount boss to move the shock closer to the position/angle it was with the original steel trailing arms, but I'm still getting the slightest interference at the bottom of the cross member at full compression. Not much more than a slight rub, but something I would like to address if I can.

I have Bilstein's for a 1985 Carrera on the car now. They are a bit larger in diameter than the earlier version but I needed them for the 14mm lower bolt. The earlier cars have a 12mm bolt. If I could somehow fit the earlier smaller diameter version on the car it would clear up the interference.

What sort of creative options are there to mate up a shock with a 12mm bolt hole to the 14mm trailing arm. I thought of installing a time-sert in the trailing arm, but I'd rather not machine the arm further and cannot find a direct 14mm to 12mm x 1.5 insert.

Otherwise how else would I modify the lower portion of the older shock or fabricate some sort of adapter to make it work? Possibly someone makes an adapter already as there are lots of custom options for coil-over installs. Modifying the shock itself is OK, but if they ever need to be replaced that might be a problem.

Here is a pic of the issue - I marked with a sharpie roughly where the shock is rubbing the bottom of the cross member opening. I have not "massaged" the opening, and now that the car is assembled, not really an option.



Any thoughts greatly appreciated.

Thanks in advance as always.

Bill

Gratuitous photo of the car in question.

[wjdunham]

One option if I can get some data which I cannot find with Google searching - is there another brand of rear shock for an '85 911 that is not as large in diameter as the Bilstein? Koni perhaps? Anyone have a pair that they can measure the diameter of the lower portion?

[Trackrash]

Perhaps you could press out the rubber lower bushing from the newer shock and replace it in the older shock bushing? I have done this with VW stuff.

[wjdunham]

That seems to be the best option. I spoke with Chuck at Elephant Racing as well, he suggested that there might be enough metal on the insert in the rubber to drill it out from 12mm to 14mm. But he did have some concern that my assumption that the earlier shocks are indeed smaller in diameter might not be correct.

Does anyone have a set of Koni shocks in an early car that they can measure for me. the Bilsteins on the car now are ~50mm diameter at the bottom. I have the set that came off but no idea what brand (they are black) and they are 45mm diameter. So that extra 5mm I think would get me what I need for clearance if I can find a new set with that diameter.

Originally Posted by Trackrash

Perhaps you could press out the rubber lower bushing from the newer shock and replace it in the older shock bushing? I have done this with VW stuff.

[aston@ultrasw.c]

machine a stud, 14mm to 12mm. Secure shock with a nut