If it holds air and not showing too much cord, run it. I land 420.000 lbs airplanes on tires that has been rethreaded several times, and has layers of cord showing (not the norm but fully legal and safe). Works fine, last long time.... 10 landings in our case. :2thumbs:
The difference is that an airplane that heavy has tires that are made different for the high load capacity, AND it has more than two tires, AND it doesn't have to go around corners at speed and still grip the road.
........ This craziness about tires only lasting 5 years is a myth that must have been started by someone selling tires. Your tires are good and there are no safety issues running them.
Absolutely false. Tell that to all the people that crashed Ford Explorers because of bad tires. Do the Google on it, most of those crashes were caused by old tires (on new vehicles) coming apart. Sure, the SUV's inherent top heavy, unstable design, was a major factor in why they crashed after the tire came apart, but it WAS the tire coming apart that started the whole crash event. Ford offered free tire replacements for anyone with an explorer with those old tires.
Rubber oxidizes and when it does, it gets harder and more brittle. So unless you keep your tires in an oxygen free enviroment, then your tires absolutely have a limited lifespan.
When the rubber gets hard, it might still hold air while sitting still. But when you hit a bump you stand a chance of the rubber breaking on the inside, like when the tread breaks away from the belts. It might still hold air, but then when you spin it at high speed this loose tread tries to fling itself off the tire. If it succedes, it will be very bad.
So in my opinion, that is very much a safety issue. And anyone is free to ride on their own tires till they fly apart, but I'm replacing mine after 4 years.
I got a new 250 rear in the dinning room waiting to be put on as I write this, I replaced the front about 16 months ago. So far this year I have bought 10 car tires, well 6 car tires and 4 truck tires anyway. One of the rear tires on my car came apart and the tread looked almost new, they were only 3 1/2 years old, but I was abusing them at the time. 3 of the 4 truck tires were separated, they were cheap tires, but only 5 years old. The other 4 were just low on tread.