To find the correct tire size, you should check one of the following:
* The sticker on the driver's side doorjamb: This sticker usually lists the recommended tire size and inflation pressure.
* Your owner's manual: This will also specify the correct tire size.
* The sidewall of your existing tires: The size is printed on the sidewall of the tire itself (e.g., P205/75R15).
Without looking at one of these sources, it's impossible to definitively say what size tires your specific 1997 Pontiac Transport should have.