It does say a max tire weight of 100 lbs, not a max tire force of 100 lbs, so I would have to believe they are referring to lbm (mass) not lbf (force), which they can't really control. Either way, I agree with Jim, the noise would drive me batty, I spend a fair amount of time eliminating rattles and vibrations in my vehicles, I wouldn't want to intentionally add one.

Sean

99 XJ Sport 2 Door, 4.0L, 5 speed, all stock. Daily Driver
79 F150 Standard Cab Short Box, 400ci, NP435, NP205, 35" SSRs