With large tires is a prepositional phrase, consisting of the preposition with and its object tires; the phrase modifies or characterizes automobiles.

Over rough roads is a prepositional phrase which characterizes run.

A prepositional phrase characterizing a noun is called an adjective prepositional phrase. One characterizing a verb is called an adverbial prepositional phrase.

Subordinate Clauses

A clause is any part of a sentence consisting of a subject in the nominative case and a predicate containing a verb in a finite form (not a participle or an infinitive). Some clauses are used as nouns; others are used to characterize or modify nouns, pronouns, verbs, adjectives, or adverbs. Clauses used as nouns are called noun clauses. Those used as adjectives are called adjective or relative clauses. Those used to modify verbs, adjectives, or adverbs are called adverb clauses.

Noun Clauses

Noun clauses may be used in practically any construction in which a noun is used.

Subject:That he is a good workman is clear enough.
Appositive:The fact that the paper is new disproves his claim.
Predicated noun:The weather will be what fate determines.
Object of verb:I saw that he had finished.
Object of preposition:The book is satisfactory except that it omits one essential feature.

Adjective Clauses

Adjective clauses are those which modify a noun or a pronoun.