15x8 wheel with 4.25 bs "biggest tire option without rub"

How about 275/60/15 on 15X8 and 4.5" backspace? anyone running this on their Barracuda?
I was wondering the same thing. With the 4.25 back space, how close to the spring is the tire?
Can I get another 1/4 inch? What about 5?
In some worlds, a 1/4 more is to much.
:rofl: