Join Date: Nov 2000
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Re: Need explaination how BB\'s can balance a tire
I'm skeptical that it would work in most cases, although it might work at times. Perhaps the lead shot has a dampening effect, rather than balancing. Why would tire shops go thru the nuisance and expense of owning a tire balancing machine and carefully place fixed weights if all you needed was a cup full of bbs? How much weight to add? Not all imbalances are equal, or even symetrical. Correct me if I'm wrong, but aren't tires dynamically balanced these days to correct for possibility that not only is the tire out of balance being heavier on on side of the circumference, but it could be heavier near one sidewall.
Centrifugal (fugal as in fugative, to flee or move away from the centre, as opposed to the word centripetal as in petition, to gather) force is the description for that curious phenomenon that drives objects away from the centre of a spinning object. Imagine a tire that is oval. One side of the oval short, the other side longer in distance from the centre. Wouldn't the short side need the additional weight? Seems to me the bb's would roll to the far side and make any imbalance caused by an imperfect circle WORSE, not better. You need weight added opposite the heavy side. Why is one side heavier? An interesting question for someone with insight into tire properties to advise us on.
I know that liquid tire repair stuff was supposed to dynamically balance motorcyle tires. Same idea as the bb's I suppose. Must work sometimes, but as I said earlier, I can't see how it could work if the tire was out of round.
Or is a tire that is heavier on one side due to it having more rubber on the inside surface, thus creating a high spot which the liquid or bb's roll away from. A perfect inner tire surface would act like a flat surface when the tire spins, and the bb's would roll away from any high spot towards any low. So if high spot = heavy spot, it should work.
Just some scattered thoughts on the subject.