will 17 in 235 45-17 in wheels in the front and 245-45-17 in wheels fit on my car! i have a 1981 635csi! and the wheels have a 20 mm offset

They will work in the back for sure, but they might hit the strut up front.

I am not positive, but I could not clear a 245/45, or a 235/50, but those are both larger than yours.

The outside diameter of the tire is correct (should be between 24.9" to 25.3") and a 235/45-17 normally fits, but it also depends on the width of the rim and the offset (ET).

If they are 7.5" or 8" rims with an ET of 20 (or less), there shouldn't be a problem.