Tire age

I have always based m tire buying on the tread left. I don't plan on changing my habits at my age. I raced on used tires in my youth without worrying and was quite lucky in that that was the last time I had a blowout. We used special formula compounds to soften tires for extra traction or to harden them for certain track surfaces. I found this interesting article on tires that mentions possible laws making it a criminal offense to drive on outdated tires.
A Closer Look at Tire Aging | Chapel Hill Tire