Slicks to Leaf Spring Space?

I have my hand, laying palm flat as clearance around my tires; 28x9x15 mounted on 15x8 rims with 5.5 inches of back spacing.

If I were you I'd look for a wider rim, a 10.5 tire on a 6 inch wide rim will loose a lot of contact area due to crowning of the tire, it also might be a little unstable.

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