What exactly do spacers do? I'd like to get a set of Firehawk rims and understand I need spacers. I'm just wondering what they do

 

The Spacers take up the space between the hub and the 4th gen wheel. If you look at a 4th gen wheel you will notice that the bolts are almost in-line with the lip of the rim and on the 3rd gen wheel the bolts are deeper into the rim.
Here my wheels with the spacers bolted on,



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WS6 Trans Am.

View My Ride @ thirdgen.org

 

In other words, they just change the backspacing of the wheel