18's require spindles?

im going to be setting my truck up for 18's but i don't have them yet, im buying some winter steelies/tires that are the same diameter/width as my 18's will be, and i want to know if im gonna need spindles or if i can get away with just flipped balljoints to lay frame, im only asking because im buying a 15" steelie and If i remember correctly you need a bigger rim to run drop spindles?