
Originally Posted by
dr. d
actually... yes.
ronki has the idea.
bullets have a rather large cross-sectional area. that is why kevlar can stop them.
nails, especially sharp-tipped nails of small caliber, have a much smaller cross-sectional area, just like the needles that are used to sew kevlar fabric into consumer goods. these needles (small, sharp-tipped nails) do not have to break thru the strong kevlar fibers. they just have to shoo aside the kevlar fibers, to penetrate the layer. i am sure, we have all seen just how sharp the nails still are, when they are removed by the tire man. so unlike the mushroomed bullets after they hit the vest.
also, bullets always slow down once they leave the barrel. the remaining force is distributed by the kevlar around it, dispersing the energy and stopping the bullet.
sharp nails being driven in by the asphalt, and sharp-tipped knives being pushed forward by the assailant's arm, do not lose that energy when they are used against (kevlar) products. so even if the kevlar manages to disperse the initial energy upon contact, there is still more energy being delivered behind it.
kevlar tires may be more puncture resistant than non-kevlar tires, but not altogether puncture-proof. and, if i daresay, they are better against larger road materiel and not smaller nails.
btw... how expensive are these kevlar tires, compared to non-kevlar tires?