Firestone dumped Ford. Your title is inaccurate.
Ford suggested tire inflation specs that were too low for the types of tires that they were putting on the SUVs. This is part of what led to the failures. What did they say, 26-28psi when it should have been 36psi? This was to make what is basically a truck feel like a car, but an underinflated tire generates more heat. This is what led to the failures.
Firestone is also to blame for building flawed tires.
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351W 89 Mustang GT Convertible