Whitewall tires were a style of tire used in 1955, which were named for their sidewall of white rubber.
When Emmett Brown repaired the DeLorean time machine after he and Marty recovered it from the Delgado Mine, the original tires were rotting and so were replaced with new whitewalls. These remained on the car until Doc's 1985 counterpart changed them for steel rims in 1885 so that the DeLorean could travel on railroad tracks.
Behind the scenes
- The whitewall tires are never mentioned by name in Craig Shaw Gardner's novelization, being described simply as "big fifties-style tires" (page 34).