I have several 3rd gen IROCS and have not yet seen wheel spacers...just picked up an 87 and there they were on the rear only. This car has standard 16" wheels.

Are these supposed to be used? I have another 87 IROC vert that has the same wheels (down to the color) with no spacers...can someone shed some factual light on this one?

The spacers were used on the aluminum drum cars. With discs, they aren't needed, but you can still use them, if you want/need your tires pushed out a bit.

The .187 thick spacers were added for the above reason in the previous post. It was also in my opinion, the engineers wanterd to keep all the dimensions to the drawning so the spacers..You just can not lose & forget about .187 on the drawnings. I got rid of mine 20 years ago.