I found similar issues, but none mentioning 15's vs. 16's...
I recently bought an '02 xterra and was looking to throw on some bfg AT's. I'd like to put on 31x10.50x15's with some 15x8 rock crawlers. The guy at discount said he wasn't sure if they would clear the calipers. I'm probably just going to have them test fit the rim but wanted to know if anyone here knew for sure. Also, one of the guys at discount said he had an xterra that required grinding down some of the metal to get 31's to fit and that was after a 3" lift... Anyone thrown on some 15's?

31" with 3" of lift will fit fine. (Okay maybe minor trimming, but without lift there will be some major trimming) (applies to 98 - 04 Frontier/Exterra).

I was running 15x8 rockcrawlers for 5 years without incident, they will clear the caliper of the X. Of course I have a frontier but its all the same, and this information is for the 98 - 04 frontier/xterra.

The 15s will clear your brakes, but the wider offset on the rock crawlers will require some trimming, or better yet, a suspension lift. An alternative would be to locate some stock 2wd Xterra 15" steelies, or some 15" Frontier rims and you could use those tires without any lift or rubbing issues.

The lift will be going on, but I was trying to get the tires now since BFG is offering a 60 dollar rebate when you buy 4. How serious is the trimming? Can I just take the mudflaps off or does it rub elsewhere?

what backspacing does your new rims have?

I'd expect to remove the flap as well as at least some of the plastic material on the flare behind it.

They're the generic rock crawlers from Discount Tire (Unique 297's). 15x8, the guy said the offset was -13(~1/2"). That makes the backspacing 3.5? or 4.5?

The mudflap is history, it wont fit.

I'm fine with ripping out the mudflap, just don't want to do major surgery on the truck since a lift will be going on shortly

There was a decent amount of trimming prior to my lift going on. As DR pointed out though, you will need to trim the front of the wheel well a bit, because the rim is wider.

u can keep the fender attached mud guard with minimal trimmin on that even with a 2 in body and 3.5 offset trust me i did it and that is what my x has but u will have to beat a little bit of the inner fender by the cab other than that its cosher ill send pics if u want to see what i have

Ive got 32s on stock wheels on one of my trucks and 31s on offset wheels on the other, the truck with off set wheels has a minor Tbar tweek and just a little fender trimming. The fender trimming is the inner lip of the fender flare where it curves in....sorry cant thing of a better explination. It at that big of a deal.