In the real world,, its about 2-3 inches,, so when there loaded the tires DO NOT TOUCH,., plus for cooling, Ya go by a truck shop you'll find that you can buy that space in about 12+ differ, wipths. Or when your out drivin about,,look at one up close, or go by a truck stop,, But Yes,, if its 1/24-1/25,, a 1/4" would be 6 inches,,about half that, if it was me,,