It's a plural noun like sugar or water. Grand prix.
Grand Prix is French, and it means Large Prize. The plural of Prix in french is the same - Prix, but the adjective Grand has to agree with it, and the plural of Grand is Grands, hence the plural of Grand Prix is Grands Prix. It doesn't depend on how many votes it gets.
Who cares what the French plural is? Once it has become a loan word, it can behave differently- no one complains that 'spaghetti' is singular in English.
Jacques Villeneuve and PBT both have valid points. However most English teachers tend to teach it as "Grands Prix". In speech though, I would suggest it's far more common to say "Grand Prixs" (pron: "grand preeze")
If you ask for the plural in English (not in French) it should be 'Grand prizes'. In French it's another fish meal.
I work in motor sport and have asked many colleagues who invariably agree that the plural of Grand Prix is Grand Prix. I think we should go with the view of the majority of motor sport experts, not English/Franch language boffins!
Prix no plural é prix mesmo, vem do francês, então só o Grand vai para o plural. GRANDS PRIX
Please be aware that any specifically named event or race, such as Long Beach Grand Prix, should use events or races as the plural, e.g. I have attended all of the Long Beach Grand Prix events.
David's answer looks the easiest to interpret and, as a magazine editor, I am going to use exactly that right now. Thanks Dave!
Grands Prix is not only wrong, its stupid. as has been previously stated Grand Prix translates as Large Prize. keeping it in the english, using the Grands Prix plural would make the translation Larges Prize... Which is obviously stupid.. And irrespective of whether its a loan word or not the translation is still its literal meaning, so its that literal meaning that has to make sense for the plural to be viable. There for, the only logical plural would be Grand Prix, as has also been previously stated, Prix is the plural of Prix. Grand Prixs (or prixes I suppose) are a close second if the Anglophone plural system insists on being employed.
I would add that what David says is definitely the most concise way of stating it.
Grand Prix (plural Grands Prix)
repected sir, would you please give more explations about it
If we accept it's a French title for each F1 race, the only way to pronounce it is "gron prie" (silent 'n') whether it's singular or plural. If we anglicise it, it's still just"Grand Prix" whether 1 or many. Anyone calling it GranS Prix just has no style...