Complex sentence: A disadvantage is that many run-flat tires cannot be repaired if a puncture occurs, this is due to manufacturer's informing the automotive industry that you cannot tell what kind of state the sidewall is in due to the compacted sidewall of rubber.
Split into simpler sentences: A disadvantage is that many run-flat tires cannot be repaired if a puncture occurs. This is due to manufacturer's informing the automotive industry that the state inwhich the sidewall is in cannot be determined due to the compacted sidewall of rubber.