I've decided to go with a 20x9 Incubus Alloys grim rim on my new 2500hd and was wondering what backspacing I need. I want to get the wheels as flush with the side of the truck as possible. I'm not fond of the tires sticking out. I'll be using the Michelin LTX A/T 2 285/55r20 tires. Backspacing options are +10 and +25

 

+25mm offset (backspacing would be a totally different measurement in inches) will sit the rim deeper into the wheel well more in towards the frame. +25mm is closer to stock as well, and with 285's I don't foresee the tires sticking out at all.