This is interesting. I have 2 costco locations close to me. One is on the way to work, one is close to home. The one that is close to home has 2 Coats machines, one the "2 position" one, and one older style you see in most shops that has the older display (not sure if thats a good description or not).

The costco by work is brand new (less than 3 months old) and has all new machines. I would THINK that they've been calibrated not too long ago, but they may very well be off. The Coats machines with the 2 postion balancers are the XBR1800 IIRC.

The reason I never thought it was a wheel balance issue is 1- I get the woomp woomp noise at 20-40, and 2- I swapped around tires all over the place and the vibration didnt change much if at all. Also, I had a bit of vibration before I even got these tires, which I bought because I found the old ones were cupped, which I attributed the vibration to, but was wrong.

I will take it by the costco next to me and have them give it another try. Thanks tiger!