FWIW, I'm also wondering if the housing is "tweaked" and/or is the rear is "square" in the chassis. But whatever it is, it seems like the Sure-Grip was absorbing some of the problem through slippage and the spool doesn't.
Strut rods and steering box tight?
The only time I had a wandering problem was when I tried 165/15 radial front tires on my bracket car.
