flat tire vs pneumatic tyre

flat tire and pneumatic tyre both are nouns.

Word	Noun	Adjective	Verb	Adverb
flat tire	Yes	No	No	No
pneumatic tyre	Yes	No	No	No

As nouns, pneumatic tyre is a hypernym of flat tire; that is, pneumatic tyre is a word with a broader meaning than flat tire:

flat tire: a deflated pneumatic tire
pneumatic tyre: a tire made of reinforced rubber and filled with compressed air; used on motor vehicles and bicycles etc

Other hypernyms of flat tire include pneumatic tire.

flat tire (noun)	pneumatic tyre (noun)
a deflated pneumatic tire	a tire made of reinforced rubber and filled with compressed air; used on motor vehicles and bicycles etc