When on difficult terrain, the pressure of the tire is occasionally lowered to insure a bigger contact area with the ground. In normal conditions, the pressure inside is enough to lock the tire on the rim and insure that the two work in perfect sync. When the pressure is lowered, as mentioned before, the possibility increases that the rim will spin without the tire, creating a flat.
What the locks, of any sort, generally push the tires onto the rims and insure that the low pressure will not become a problem. The beadlock options divide in two main classes: internal and external.
The external ones will bolt on the existing rim (given it’s prior modification) or will incorporate the system at purchase. What it effectively does is clamp the tire in between the outer and inner rings, thus creating an excellent contact area for the tire not to slip off. On the other hand, the inner locks, which are essentially invisible are nothing more than high pressure tubes that push the bead of the tire against the wheel, insuring that it won’t move. It’s generally fabricated from a strong polyester which will keep the beadlock from inflating too much inside the tire.