Most blowouts are failures due to under-inflation. Nearly everone knows that they should check tire pressures. Almost no one really does it as often as they should. Tires that are run under-inflated develop excessive heat leading to a failure. There are also some due to manufacturing defects in the tires. Auto manufacturers are rarely the root cause for the failure.
[Yes, this does include the Firestone/Ford Explorer silliness from a few years back.
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