When the wheel is in a static/constant motion I feel safe that they will find their home. What happens to those beads during mild to hard braking? What happens to them on irregular roads? Add in plugs and everything changes, which of course should include the TPS. Machine testing in a controlled environment will not replicate what we get on the street. Finding that light spot and fixing a permanent weight removes the variables you have with free floating beads, I wonder, do MX riders use these?
Under mild braking, the centripetal force of the rotating wheel is stronger than the inertial force of the braking. Hopefully I'm using the terms correctly. At some point, the braking forces can/will overcome the spinning forces and the beads will start rolling within the tire. The heavier the braking, the higher the speed where the beads will "destabilize".
As a side not, the beads will take somewhat longer to stabilize under heavy acceleration, based on the same principles.
As I understand it, the beads require some irregularity in the road surface to function properly. They also require a minimal speed (about 20-35mph IIRC) to stabilize. If the road is so irregular that the minimal speed cannot be maintained, the beads will be ineffective.
The difference between tire plugs and TPS, as far as the function of the beads is concerned, is the location of the "obstruction". The TPS is on the wheel, while the beads are "thrown" outward, and do not come in contact with the TPS in normal operation. The rope plug is in the area where the beads flow, but the beads will flow around the plug without restriction.
The beads are not recommended by the manufacturer for racing. I have no information on whether any MX's are using them.
More information is available on the mfg's website:
http://www.innovativebalancing.comsLike all products, they fit some users and applications better than others. For a sport rider that goes through tires in 3k miles or a racer, they make little or no sense at all.
