backspacing

im buying some 20x8.5 to go all around i have a 90 s-10 and need to know the backspacing so i can tuck and also what size tire should i run would 245-35-20 be ok? thanks guys

bump

just ordered some 20x8.5 myself. mine are 5.4" of backspace. which is 16.5 mm offset.

245/35/20 are perfect for an 8.5" wheel.