BITD, manufacturers used to put a paint dot on a tire's heavy spot, meant to mount opposite of the valve stem. I had a vibration once on my Alfa, turns out they mounted the dot next to the stem. From what I understand, they've gotten away from that. With 5 cars, I'm a regular at my Discout Tire Shop (6 winter/summer swaps per year)
Ever since, when I have new tires for the Beck and the Porsche done, I tell them I want my tires balanced to 12Omph.
My original statement above was I chased a Front End hop....
Over here I have the same issue, plus they charge for storage of the summers then storage of the winters and tire change fees, Finally I spent so much time just going there and waiting that I decided I had enough, it would be easier for me to do it myself, not to mention that, believe it or not, it was costing me nearly 1K per year for tire changes, go figure, solution: buy a second quickjack 5000lb unit and now I do my own cars and it is in an out faster than travelling to the local shop, that quickjack got paid in one season.