I'm looking into buying a used 91 Firebird, but one of the previous owners modified it so that the rear wheels are sticking out past the quarters. I'm not a big fan of this look, so before I really consider buying it, I'd like to know how easy it would be to convert back to the factory look. The guy says that there are no spacers that they just had "offset wheels", but he hasn't really done anything with the car it seems. I know the 4th gen rear end is wider, how would I be able to really tell if it has a 4th gen rear end on it? Are there aftermarket wheels with a deeper offset that would push it out further? How can I measure the wheels/rims such that I know if it's stock wheels or not?

 

If there are really no spacers (check) measure the width of the axle. To measure the wheel backspace you need to take the wheel off and measure the distance from the rim to the hub. Stock is 4.5 inches(?). You would need to swap back to a 3rd gen axle or get 4th gen or other wheels with correct back space.

 

Is it just the tire that's past the well flare or is the wheel actually sticking out that far ?

If it just the tire it could be as simple as some one putting a very wide tire (295/50r15) on a stock wheel.

Or it could be a very wide tire on a wheel with a 3.75 BS or similar.

Knowing the tire size would be first then use the diagram below to measure the width then the BS with the tire laying on the ground with the back facing up.