We don't have synonyms for mag wheel yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are big wheel, rag wheel and car wheel.
(n) :
(automotive, originally late 1950s and into 1960s) A wheel for a motor vehicle, made from an alloy of magnesium, typically lighter and offering better heat conduction than steel wheels; often styled in a five-point star pattern; (sometimes also) a wheel made to look like such wheels but not truly of magnesium.
(n) :
(automotive, originally late 1950s and into 1960s) A wheel for a motor vehicle, made from an alloy of magnesium, typically lighter and offering better heat conduction than steel wheels; often styled in a five-point star pattern; (sometimes also) a wheel made to look like such wheels but not truly of magnesium.