We do sell used wheels in good condition at our 3016 Minnehaha Ave location. You're welcome to stop into any of our locations to inquire about current scrap that you could have at not cost. The Minnehaha shop would have the most scrap at any given time, but all three Hub locations have scrap piles for discarded or worn wheels.
Not sure about free but wheels discarded from previous folks bikes are always available.
There's a bike shop on Chicago between 35th and 36th that sometimes has tires, wheels and tubes. They'll usually be in the back of the building.
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