Sluggo:
Drag racing like tall, soft, squishy, flexible sidewalls. To get the 22-24" tall slick that a typical import racer runs onto a 20" rim you'd have a 1" sidewall. Or basically a rim painted with rubber. To get the desired 5" tall sidewall they use a smaller rim. The reason for the desire for the tall sidewall, is that as the tire compresses down, it's contact patch increases in length. Which is a very good thing. non-import drag racers typically run 15" rims because of the need to get the brakes and axles to fit. And they're more likely to run 29-33" tall slicks, so it's not a problem. They just gear down. The taller the tire, the larger the contact patch, though the larger the tire, the more power you need to turn it. It's a balencing act.