I have coffee with a group of guys and one of them is a bridgestone tire rep... he's ready to retire, I think another 6 or 7 months... he does not suggest them for tires smaller than 19. 5" rims, hes sees some reasonable results in larger 315/425 22. 5" used on heavy front axle trucks, examples are cement trucks, cranes, etc with 16,000 lb front axles... . I understand this as I own a truck with a 16K lb front axle, with 315 22. 5" tires and a balance problem... we decided that those rings would not be a good answer for our problem... .
Kevlar is a tire cord material, like rayon, nylon, steel, polyester, etc... . Kevlar is a Dupont trade name with Aramid as the generic name... . Kleenex is the trade name, tissue is the generic name...
Kevlar is a fibered material that is about 5 times stronger than steel pound for pound and is used in friction as well... its also the bonding material that holds the shuttle tiles together... .
Today tire sales people use the work Kevlar but most really have an Aramid material in them... we use Aramid in some clutch facings because some of the Dupont material is not available...
Also, Kevlar is used in bullet proof vests...