Tires have come a long way, how often do you get a flat tire? I don't remember changing one since I owned a vehicle.
But when the ol' bias plys were out, it was a regular thing!
I worked at Firestone in the '70s as a tire changer. Firestone was replacing their 500 series with the 721 series. The 500's had a problem with separation which would result in knots appearing in the tread. When I commented on tires, it was that I have seen fairly small incremental improvement sinc the 721 series. Batteries - a fairly significant jump when the alkalines came out - but since then small incremental improvements. If you look at TV's or digital cameras, the significant jumps have been numerous and often - just sayin...
