* G60-15: This was a popular size, especially on base models or those without performance packages. These are bias-ply tires.
* L78-15: This would likely be found on performance-oriented models and could be a bias-ply or radial tire depending on the specific build.
To know the *exact* original tire size for a specific 1979 Firebird Formula or Trans Am, you need to check:
* The original owner's manual: This will list the recommended tire size(s).
* The tire placard: This sticker (often located on the driver's side doorjamb or glove box) will specify the original tire size and inflation pressure.
* The car's build sheet (if available): A build sheet documents the factory specifications of the vehicle and will detail the tires fitted.
Keep in mind that any tires on the car now are unlikely to be original unless it's a remarkably well-preserved, low-mileage example.
