If you're adding a bunch of weight, I can see it acting as a damper.... That's the only logical reason I can come I with.

Weight as in wheel weights to balance it or the weight of the balancer we're installing? Because I dont think there is any wheel weights being installed with it and the weight of the balancer is not much at all.

I dont think these are the same brand that we use but it's the same idea.

http://www.centramatic.com/Page.aspx?page=Demo

By doing something like this you're also balancing the entire hub/drum/wheel assembly. Not just the wheel.

Has anyone else notice that dunlops seem to take a crap load of weight to be balance. I have never like dunlops but the few times I have ran them they take a lot to balance.

Not sure about motorcycles, but cars have something they call "road force balancing".

I personally just use a dial indicator to get the lowest runout I can.