So after I got back from the big Bonneville/class reunion road trip, it was time for new tires. I got a new set from my local (west coast) Les Schwab dealer 'cuz I have one in my town. The fronts always seemed to have a balance problem, which they tried to correct after 3 tries with no results. As a last resort, they offered a "road force" balance, which includes probes to check wheel & tire runout and also includes a large roller that applies about 1200 lbs. of force against the tire as it's spinning to recreate the tire/wheel under load. Turns out that one of my wheel/tire combos had all the factory imbalances aligned at the same spot on the wheel, enough that a traditional spin balance couldn't overcome. They marked the locations on the tire & wheel with chalk, let the air out of the tire, and rotated the tire on the rim to offset the two imbalances. Took it for a test drive, and perfect! This may be old news to many of you, but all new to me, and I'm glad to find it out.