Quindi per esempio se voglio dire ad un amico "Sei fuori strada!" riferito ad un tentativo sbagliato di indovinare qualcosa, posso dirgli: "You're out-street/off the track" ? Non so, ma non mi suona. Non c'è un altro modo per dirlo?
To clarify some of the suggestions from 13 years ago: assuming the context from #3, "you're on the wrong track," "you're way off," and "you're barking up the wrong tree" (and Janekels "you've got it wrong") are all fine, but "you're astray" isn't idiomatic at all, and anything to do with being off track (as opposed to being on the wrong track) means something different, to me at least. To "get off track" or "go off track" has to do with getting distracted and talking about things irrelevant to the question at hand. I wouldn't use "to be off track" to talk about someone who's "on the wrong track" in trying to guess something.