Hello ... i am getting 315/60/15 for my Buick Riviera 1971 so what is the rear wheel width and BS in this pic ? Thanks
There's absolutely no way to know the backspacing on those wheels by just looking at a picture, unless the actual owner of that car is a member here and sees the picture. Folks can lob guesses, but again, there's absolutely no way to KNOW from a picture like that.
While I can't help you with the back spacing I can tell you that the minimum wheel diameter is 8.5 inches for that size tire and the maximum diameter is 11 inches. I would recommend at least a 10 inch wheel. Why don't you take the car to your tire dealer and have him test fit the wheels you are buying on your car. That should give you an idea of the offset you need. My best guess would be 5 inch back spacing for a 10 inch wheel but, purely a guess. As long as you keep the sidewall of the tire away from the frame rails, your wheel well opening should allow any size tire you want as long as your car doesn't squat too much on turns or fast take offs.
I am no expert by any means and any "expert" out there would never tell you oh yeah those are such and such by looking at a picture. The car in the pic looks like it may be slightly lifted as well to fit those. Here is a good start for you to figure out what your car can fit; http://www.thewheelfit.com/ And; https://www.summitracing.com/parts/php-01201
Not to be rude, but can you tell how long a board is just by looking at a picture of it? Within a 1/4" with no scale to go off of? And what if you couldn't see half of the board? That's basically what you're asking someone to do for you on these wheels.