Everything I've heard about Dynabeads says they don't work. Buddy tried them on a dealer's balancing machine. Mounted the tire with no weights, gave it a whirl, it specified a couple grams in one spot. Added the dynabeads, spun it again, exact same reading. On their website they even admit this, but somehow claim the wheel is balanced even if the machine says it isn't. You'd also have to somehow be extra sure no tire lube gets in the tread, otherwise they'd all just clump up and really screw things up.
If you think about it, not really too difficult to see why it won't work. Wheel picks up speed, all the little beads are flung against the outer wall and held there by centrifugal force. Unless there's big "dents" on the inside wall for some reason, they're going to just add weight evenly all over the tire and balance nothing. You'll have a slightly heavier, unbalanced wheel. They work on the assumption there's a physical deformity that's precisely the right size and in the right spot so as to adequately balance the tire. Somehow I just don't believe that.
It's another $20 or so, just get it done right. Stability and safety aren't something I'd want to skimp on and replace with some gimmick.
Unsurprisingly, HD forums seem to love them, and everything from Vespa to Goldwing riders don't.