How to check "roundness" of wheels?

[Fred K-OR]

I think I have posted on this problem before but still have not solved my problem. Sorry about a repost.

But my problem is that with my 29 coupe when it goes down the road at low speed ( 15 to 25 MPH) it seems to "bounce" up and down. It doesn't "waddle" back and forth like a duck but rather seems to go up and down.

I have about 8 or 9 21" wheels around here and am trying to find which ones are "round". That is one that would not cause a rig to "bounce" up and down. I tried various methods, putting them on a hub and rotating then and trying to measure how much they go up and down when having them close to the floor, and other measurement methods. But so far have not found a good way to measure the roundness of a wheel either with or without a tire on it. Does anyone have any good ideas on how to check a wheel either with or without a tire on it or is there some kind of tool to check this?

I could have the possibility that one of my tires has a high spot on it. But they are almost brand new Firestone tires and find this hard to believe, but-----. Or is there another reason for this problem?

Thanks for any ideas you all may have.