Let's play educate the idiot...what is backspacing? /forums/images/graemlins/blush.gif how do you measure it? etc. I'm looking to replace my existing rims on a D44 & 12b w/ 15x8 wheels & 33x10.5 tires. I think I need the 3 5/8 backspaced rim??? I currently have 15x8.5 wheels and 31x10.5 tires.