idle wheel vs idler pulley

idle wheel and idler pulley both are nouns.

Word	Noun	Adjective	Verb	Adverb
idle wheel	Yes	No	No	No
idler pulley	Yes	No	No	No

As nouns, idle wheel and idler pulley are synonyms defined as:

idle wheel and idler pulley: a pulley on a shaft that presses against a guide belt to guide or tighten it

Other synonyms of idle wheel include idle pulley.

idle wheel (noun)	idler pulley (noun)
a pulley on a shaft that presses against a guide belt to guide or tighten it	a pulley on a shaft that presses against a guide belt to guide or tighten it