[HarryD]

I had the same rub develop in my lowered 1973.5 911 when I got new tires that had more of a square profile than the tires that were replaced.

After consultation with Steve Weiner and Jeff Gamroth, they concluded that the rub was occurring when the rear squatted on acceleration. Based on our conversations, it appeared I had two options:
1-Raise the car (I like the current look and superior handling and, hence, I did not like this choice); or
2-Install turbo torsion bars (21 mm front/26 mm rear) to reduce the squat.

We went with option 2 and I have had no problems since. I will add that my ride on the street was not degraded with the slightly stiffer bars.