I looked here
to verify what the numbers mean. A stock JK tire that I found on this
site shows SBRP255/70R18 as a stock tire. The diameter of the stock tire on a JK is as follows:
Sidewall height: 70% of 255mm = 178.5mm /25.4 mm/inch = 7"
Total diameter of tire = 18" + 2 X Sidewall height of 7" = 32"
Tire width = 255mm / 25.4mm/inch = 10"
Rim width = 7.5"
The diameter of your tire 315/75/R16 is:
Sidewall height: 75% of 315mm = 236.25mm / 25.4 mm/inch = 9.3"
Total diameter of tire = 16" + 2 X Sidewall height of 9.3 = 34.6"
Tire width = 315mm / 25.4mm/inch = 12.4"
Your Rim Width?
The important information would be the manufacturer's maximum limits on tire size given your rim size. If those limits are exceeded and problems occur, then warranty could be effected.
The width of the tire if placed on the stock rim, will it work? If wider rims are purchased, can they be legally run on your vehicle? Some states have limits on how much the tire sticks out from the vehicle. I have heard from people that tickets can be issued if the tires stick out too far but don't know how this is determined.
I would think a tire sales place may have some handle on this. Maybe some people can post on the subject and bring it into better focus.