Backspacing Question

Ok, I am currently running 31x10.50's on a 15x7 with 4" of backspacing. I just got a set of 32x11.50's that I want to mount on a set of 15x8's that my friend is going to sell me... except they are 4.5" backspacing. I really don't want my wheels to stick out any less than they do now.

I got thinking about it, 4" of backspacing on a 15x7 theoretically leaves 3" of wheel sticking out past the wheel mounting surface. On a 15x8 with 4.5" of backspacing will then leave 3.5" sticking out past the wheel mounting surface, and therefore will actually stick out .5" further than the 15x7 despite the increase in backspacing. That coupled with a wider, more square tread on the BFG KM's vs my current Trxus MT's I'm hoping will still give me a hair wider (looking anyway) stance.

Does anyone else follow this? Does it make sense? Or am I retarded? It would save me $100 to get these used wheels but this is the only thing I'm hung up on.

You're thinking backwards it's going to have the wheels closer together than further apart. The 15x7 is 3" BS which has 4 inches outside the WMS, the 15x8 is 4.5" BS which leaves 3.5" outside the WMS. For a wider stance you want a smaller BS which is why 15x10 is usually common in 3-4" BS.

The 15x7 has 4" of backspacing, making it 3" outside the WMS, I agree with what you said about the 15x8. Therefore, aren't I looking at 3" dished out with the 15x7 vs 3.5" for the 15x8?

The inside of the wheels will be 1/2" closer with the 4.5" backspacing, but since there is another 1" of rim width the other 1/2" will be sticking out the side...

...only if your hubs were flush with your fenders...

What? Is it not true that you measure backspacing from the back of the rim? If you have a 15x7 and a 15x8 both with 4" of backspacing, that 4" between the back of the rim will not change, only the spacing out in front of the rim. So in actuality the 15x8 will stick out 1" further than the 15x7. So in going from a 15x7 with 4" of backspacing to a 15x8 with 4.5" of backspacing, I'm gaining the 1" in width but only 1/2" will be sticking out because I gained 1/2" in backspacing...

I'm following you... what's your question? Seems to me you have a firm grip on how the change in backspacing is going to affect the position of your wheels.

Either way 32x11.50's will rub before you get near full lock. If you want a wider stance look and to prevent rubbing you need wheel spacers.

I geuss all my question was was whether or not my wheels would be sticking out anymore than they are and whether or not my logic was making sense. I think I may just get the wheels and maybe spacers later if I want.

Why not save the money and use the wheels you have !!