What causes a tire bubble or tire bulge?
Impacts cause belt damage and belt damage causes the bulge
Potholes and curb kisses can severely damage the steel belts in your tires. An impact can cause the belt to separate, causing a bulge or it can puncture the inner liner causing a bubble. In either case, the tire is damaged beyond repair.
Driving on a tire bulge or tire bubble is dangerous
When the steel belt punctures the inner liner, air bleeds between the radial plies and the sidewall, causing a bubble. If you continue to drive in this state, the air will move to other portions of the sidewall, resulting in catastrophic failure.