I'll be putting on a set of 31" BFG ATs 15 X 10.5 on black steelies with a 4" offset. My question is - with this offset will I have any trouble mounting the spare on the stock carrier. I read the gazillion posts on 31" spares but couldn't find any talk about a 4" offset wheel. A few ID'd offset wheels as possibly requiring some mod to the rubber bumpers but they didn't specify the degree of the offset. Thanks for the help...
My 33x12.5 on a 15x10 with 4" backspacing wouldn't fit on the stock carrier. There wasn't enough thread on the lugs to get the nuts on, and it was hitting the bumper. I had to buy an extension (then strapped it down with a ratchet strap because it bounced all over the place). Hated the extension, and finally replaced it with a bumper/tire carrier recently.
It's not a 31, but similar as the BS and the wheel size are the same as yours. Hope maybe that helps.
Try it and see. If it doesn't work, the extension is not that expensive.
4" of backspacing is 4" from rear of rim to the hub mounting surface. So it doesn't much matter the width of the wheel. If the tire gets too wide then that is a different story. I had 31x10.50x15 BFG AT/TA mounted on alloy 15x7's with 3.75 bs and it fit fine. The stock wheels have more backspacing than your steelies. The rub comes with the 3rd brake light. At the most you may need a coulple of washers to lift the light a little.