[Mahler9th]

As you know, we have quite a few 911 racing cars running 16" diameter 13 inch wide bias ply slicks. Some are still using up their Goodyear inventories and a few are experimenting with Avons. I suspect that when everything is said and done, most will convert to 16" Hoosier radials, as there is no solid visibility on the ongoing availability of Goodyear bias plys, and the Hoosier bias plys are considered less desirable form a performance standpoint.

As to your question, I think the weld-on Hamlin Rear Control Arm Pivot Boxes may be what you are looking for. They used to be sold by SmartRacing Products (SRP), but that company is no longer in business. Many of the products from the old SRP catalog are available from Jerry Woods Enterprises-- I am not sure about the pivot boxes. I can check with JWE tomorrow at Sears Point and get back to you. The SRP brain trust will be there as well.

It looks like Tarrett sell similar/identical rear pivot boxes. Ira Ramin at Tarrett can help you understand whether they will work for what you intend. He knows his stuff for sure. I suspect they will.

On my car with SC trailing arms, I wanted to get ~0.75 degrees of negative camber for best performance versus wear. With stock spring plates and a super low ride height, this was not possible. So I had to modify the spring plates. As you may know, the stock plates and the 935 style plates have a slot for camber adjustment and a hole. I basically had the slot and hole on each plate welded up. Then cut a new slot and drilled a new hole on each plate. As I recall, these are about 10 mm lower than the normal street car slots/holes. I will check my records.

By doing this, I was able to get as little as 0.5 or so of negative camber with my low ride height without having to change the inner pickup points.

The geometry changes afforded by the Pivot Boxes and 935 style spring plates add performance potential and make it easier to set camber and toe. From a performance standpoint, I suspect it is less than one second per lap. I am currently not motivated to spend ~$2-3k for a second a lap.

Since you already have the spring plates, you can probably just modify them like I did to get the camber you want.

In my case, a change to radials will necessitate a further hardware change as I will want 2-3 degrees of negative camber.