what size tires is this model supposed to use
Should be a sticker on the driver's door or door frame that will tell you. Barring that, I believe these used something in a 14" tire. Any good tire shop will be able to tell you the recommended OEM tire size.
I have a 1994 Nissan Sentra too, and the size and spec tire for mine are 175/70R13. They're probably the same for yours.
175/70r13 if it's a 13"rim 185/60r14 if a 14"rim
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