RGMN

That's actually what I was thinking it could be.

I remember a customer years ago that absolutely had to have a certain bike but we didn't have his size. He ended up buying one in a different size, I don't recall if he ended up on a smaller or larger frame, but he was big guy and he came in complaining of a vibration on the bike. None of us wrenches could replicated it. One of our genius sales people invited the guy on a shop ride, and we got to see him ride the bike. He sat very upright and was way back on the bike. A majority of his weight was on the rear wheel. Once we got going sure enough the bike started to shimmy. We told him to lean forward and it stopped. The shop owner setup a swap to the right size bike and the customer didn't have a complaint after that.