Hi
I heard/saw/read somewhere that Kevlar was invented initially to be used in manufacture of tires.
Program on TV the other day where chase police shot out the tires of suspect vehicle to make him stop.
So why are tires not bullet proof?
If tires are not bullet proof how do military vehicles with those big all terrain tires not get stopped and disable by a single strategic shot???
Kevlar has many more uses than in bullet-resistant vests, more properly called body armor.
It is a synthetic fiber with a very high breaking strength. In tires, it would replace the steel and polyester belts that hold the carcass of a tire together (a tire is not just a hunk of rubber shaped like a donut).
Wheeled military vehicles often use a magnesium or hard rubber insert that keeps the rim from hitting the ground when the tire collapses. Ride quality sucks but the vehicle can keep rolling without losing the tire. Commercial runflat tires use either an insert or a bead lock that keeps the tire from coming off the rim.
Nothing mobile is bullet-proof. Bullet-resistant, maybe, but not bullet-proof. Even 1/4 inch steel plate used in executive limos is no proof against the good old Browning .50 round.
To continue the armor resistance thing, the US Army’s M2/M3 Bradley Fighting Vehicles’ sides are not completely resistant to even 7.62mm machine guns at close range.
If you step up to the M1 tank, it is essentially impervious to all small arms fire but it’s Armor-Piercing, Fin-Stabilized, Discarding Sabot round is really just a big, fast-moving bullet and capable of defeating any armored vehicle in the world.
Good post!
Re the OP - kevlar is not automatically “bullet proof” or even bullet resistant. It needs to be woven and layered appropriately to capture a bullet and absorb its energy. Lesser fibres such as drawn nylon and silk can be woven into good soft armour as well. Carbon fibre is stronger than kevlar, but doesn’t have as good energy-absorbing properties (elasticity) and so hasn’t been used for this application as far as I know. Spider silk is very promising, but you can’t get enough of it from spiders. Genetic modification of other organisms may create a source of spider silk. And it may find other uses unrelated to armour.
When I was wearing the stuff to work, it made good sense to learn how it worked. 
Sort of along the same lines, a tire company back in the 80s or so, advertised a tire which basically had a sandwich design with a layer of Fix-A-Flat type goop inbetween that was supposed to seal any punctures in the tire. No idea of how well they would have worked. I’ve often wondered why someone hasn’t come up with a decent foam filled tire, so we’d never have to worry about checking the air in our tires again.
Yeah, I’ve seen those. I’m gonna wait until they show up on military vehicles and prove themselves in combat before I consider putting them on one of my cars. They just don’t look too sturdy to me.
I think that’s probably a likely proving ground for this technology (mentioned here, along with some interesting info)
Michelin’s site shows some prototypes working decently on some heavy machinery already.
It doesn’t take nearly that much to puncture steel plate. I’ve made targets out of cold rolled 3/8" plate that were heavily cratered and quickly punctured by 5.56mm at short range. If I get a chance I may do some tests with half inch plate and a cache of .30 caliber AP I have. That ammunition is the only true armor piercing type that isn’t prohibited by federal law but should have about the same ballistics as 7.62mm NATO though probably a bit better performance due to a heavier bullet.
The thing that concerns me is they don’t show any shots of the wheels working in a muddy, watery (say slightly flooded roadbed) or snowy environment. All those open spaces are just prime targets for getting loaded down with gunk, and then when you hit pavement and begin driving at a fairly decent speed, that stuff is going to go flying.
I know, Padeye. I’m whacking a fly with a sledgehammer for emphasis.
I’ve punched through half-inch plate with my Garand. The jacketing siezes in the hole but the lead goes on through. 3/8ths plate might as well not be there if it gets hit dead-on with a modern military round.
At what ranges are you guys punching this stuff? I’m used to thinking of 100m as short range for this kind of data and 3/8" as being proof against 7.62x51mm FMJ at 300-500m or so. Are we just thinking in different orders of magnitude or what? I approach armor penetration thinking as a machine gunner or a scoped-rifle marksman (I’d never self-apply the term sniper - I’m not that disciplined).
Short-range. Most of the stuff I’ve punched has been at 100m or so. Usually because I don’t feel like walking 500m to check my targets all that often! 
It’s not uncommon for off-highway equipment (tractors, skid-steers, etc.) to have foam-filled tires. They don’t use special tires for it, just fill regular pneumatic ones with foam (done at a tire shop that has the equipment). It’s pretty expensive though (around $90 per tire for the front tractor of a small utility tractor–about the same size as a sedan tire).
Good call - Ok, the final product would surely have the side blocked off (perhaps transparent for kewlness) because like you said, mud or (definately around here) ice and snow would make for seriously unbalanced wheels.
Thinking about it more, I can also imagine some regions might have critters nesting in them, and if they don’t chew it up inside, the mess they make when you spin them around and around and around and around wouldn’t be pretty 
Oh! And if even if you sealed it up, a leak might let water in which wouldn’t be good… ok, lots of things left to solve.
Tangentially related to the OP, but Kevlar is used in marching band drumheads. While not bulletproof, or bullet resistant, they are virtually unbreakable in normal use. If the head breaks, it’s because some component other than the Kevlar failed – such as the crimping around the edge.
And, also by some kit drummers as well—usually hard rock or metal-type drummers, though the odd popular-style drummer will use them. I don’t know if Ricky Lawson still uses a Kevlar head.
And, just a few years ago a company was marketing these for normal drumkit use, in various models. The company didn’t last, though; speculation suggests that the heads lasted too long to turn a profit for the company.
They aren’t without certain disadvantages, though. For one, I absolutely dislike the ‘crack’ sound they make when tuned tightly in marching bands (which is the fashion these days; easier to play intricate figures, I guess). Secondly, they feel like hell when used on a snare drum and cranked for durability—they feel exactly like a piece of wood. This non-giving nature can easily lead to tendonitis and CTS.