To adjust, remove rear wheels, use a flat bladed screwdriver in one of the lug bolt holes (use a flashlight to line the hole up with the adjusting wheel)
I've peered thru the lug nut holes around the entire circle using a flashlight and I can't seem to locate this adjusting "wheel" anywhere.
My car is a '91 300E. Where on the clock is this adjuster located, and what does it look like?!