So, I put this post together for all of you, I’m not the 100% Author of all this.
First things first. Jeeps come stock with 2 different tire sizes:
1. 225/75/16 (29”x9”)
2. 255/75/17 (32”x10”).
The backspacing on stock JK wheels is 6.25". That means that the mounting surface of the wheel is 6.25” from the rear lip of the wheel. The larger the backspace number, the further under the fender (and closer to suspension components) the wheel will be. (see below image)
I see posts all the time saying that a 33” tire will fit the stock JK just fine, and that is semi-true. In reality, this question requires a 2 part answer. The first part deals with tire diameter. The second part deals with width.
It is true that the largest diameter tire you can fit on a stock JK without issue (read on) is 33” in diameter. With this diameter, you shouldn’t have any issues on the street. However, you could get some contact with your fenders if you flex offroad. Disconnecting your front sway bar will cause contact with your fenders.
Now let’s take a look at tire width. People often overlook this aspect when choosing a tire. The width on most 33's range from 10” – 12.5”+.
On Stock Wheels:
The largest tire you can fit without a chance of problems on road is a 33x10 tire . An example is the 255/80/17 BFG. Because this tire is the same width as most stock JK tires, there is no issue on road, despite the larger diameter. You can run this size without issue.
Now, let’s consider some tires that could potentially cause slight issues on road; the 33x11s. (The common sizes of these would be 285/75/16 and 285/70/17)
Any tire larger than 11” in width, you are almost guaranteed to have to do some mods. In fact, if you go too much wider than the 11” tire on stock wheels, you stand a good chance of making contact with your rear swaybar end link. If that is the case, wheel spacers can correct this issue. Common sizes are 295/70/17 (33x11.6), 305/60/17 (33x12), 305/70/16 (33x12), 295/65/18 (33x11.6).
On Aftermarket Wheels:
As I mentioned initially, the stock wheels have a backspacing of 6.25”. This is too deep of a backspace to allow proper clearance for a decently wide tire. The general consensus is that the “magic number” for backspacing for the JK is 4.5” or less. It does not mean you can't run a wheel with 4.6”+. But 4.5” and under is the safest bet.
Many 15” wheels have less (sometimes a lot less) than 4.5”. That's so the wheel clears the brake calipers. Most 15” wheels come with 3.75” of backspacing. There are a few that come with more and some that come with less. Just remember, the lower the backspace number, the further out the wheel will sit from the Jeep body. Also, be aware that, while many 15" alloy wheels will fit over the Wrangler's brake calipers, most 15"steel wheels will not.
Once you get into 16”+ wheels, it's pretty easy to select a wheel with a backspace near 4.5”. The most common 33” tire to run with 16” aftermarket wheel is the 285/75/16. A common tire size for the 17” wheel is the 285/70/17.
I shared this video few years back, i think you should always take a look at it when considering a new tiers
https://www.youtube.com/watch?v=zlFiJnA ... ata_player
Below posts can also be helpful:
http://www.ad4x4.com/club/viewtopic.php ... JK#p306194
http://www.ad4x4.com/club/viewtopic.php ... JK#p212332
