I had the orignal Firestones 42,500 miles tread looked as new had a sidewall stress test cracked all around the tire, the tread was ready to come apart, Ford had this problem some years back,

 

I had the original Firestones for approx 40k miles and had no issues with them.
I replaced them, as I always do to avoid tire problems before they arrive.

I bought the same tires because they were quiet, good traction, and were at a good price at the local Firestone training center. I read all the discussions here and felt like these were good for me and since we do not NORMALLY have snow issues, it would be ok.

The tires did very good in the snow here in North Texas last month, and yes 12" was enough snow to be able to claim as "snow days".

Now have 48K and happy.

 

Had 50k on my firestones and they still looked okay but since the highway took two of them out due to a turned up reflector, I upgraded to 18inch wheels with some contis.

 

What most people call "stress" and "dry rot" cracks are just normal cosmetic cracks on the sidewall caused by heat and flexing. However there is such a thing as "dry rot" when the rubber gets to be too old and looses elasticity, like an old rubber band that appears to be burned and brittle. Remember tires are made of high carbon content rubber.
The problems that Ford/Firestone had involved de-lamination of the tread, which would present as a very deep groove forming around the tire just below the tread line, it would look like you had a really bad recap job (if you are old enough to remember them).
I have not had any issues whatsoever with Firestone tires on several different vehicles, I have however experienced getting 2 different cars rejected at safety inspection for "dry rot" my wife and my mother both measure tire life in decades, not miles, not years! My wife's 1999 Mazda just turned 30,000! had to replace 2 tires last yearly inspection

 

pictures?

 

Sorry no pics. But the "rotted" sidewall looks a lot like a piece of pine turning into charcoal and can actually be scraped off with a bit of effort. Looks like it has actually been in a fire. The de-lam I have not personally seen, except on old clunkers with really bad alignment where the steel belts start to walk out of the worn edges of the tread, that is scary enuf. I have not been in the tire biz for like 35 years, but I remember getting stuck and cut up by those steel belts a lot.

 

They sure don't sound safe to me anyway...

 

What's the date code on those tires? IMHO, depending upon year, the tires are in need of replacement. As was mentioned some cracking over time is normal. Look on the sidewall of each tire and reply back here with the 4 digit date code. Also attempt to take digital images and post them here.

If you are not familiar with the date code location, go to Tirerack's website and search date code or the National Tire Manufacturers association website.