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"What size tire will fit my FJ?" is by far the most asked question here on the forum.

The short, and most accurate answer is, "It depends." There are a lot of factors involved.

I'll be posting charts of what fits stock, with a body mount chop (BMC), and with BMC and lift.

WHEELS:

Proper tire fit starts with proper wheel dimensions. See this post on wheel dimension explanation. The factory wheel size is 17"x 7.5", with a 6 on 5.5" (6x139.7 mm) bolt pattern, with a 106.1mm hub bore (aka center bore), and a 15mm offset (or 4.84" backspace), which is laid out in this post. Lug size is 12×1.5 pitch.Varying too far from the factory offset will result in component and/or body contact problems, and/or subtle or not-so-subtle handling differences from stock.

Please note that you must run at least a 16" diameter wheel to clear the brake calipers. Not all 16" wheels will fit! See this post for a list of 16" wheels that can be run without spacers. When in doubt, run a 17" or larger wheel (though if you're running 22" or 24" wheels, you need to post pictures so we can all make fun of you).

Please note that different wheels have different offsets/backspacing, and construction, which makes exact predictions almost impossible. See this post for more on wheel measurements.

TIRES:

Not all tires of the same size are actually the same size. A 285/70/17 Dunlop highway tire may be of a different physical dimension that a 285/70/17 Goodyear mud tire. Consult with the manufacturer's website for the exact tire you are considering to see what the actual diameter is, if you think the fit will be tight.

Before you start asking questions, be sure you know how to read a Metric tire size: e.g. 265/70/17, where:
  • 265 is the tread width in millimeters,
  • 70 is the aspect ratio (sidewall height as a percentage of tread width, so 70% of 265mm = 185.5mm), and
  • 17 as the rim diameter in inches.
So a 265/70/17 should be 10.43" wide and 31.6" high (here's the math: 265mm wide = 10.43" wide. 70% of 10.43 = 7.3" but we have 2 sidewalls - one on either side of the rim - so add 7.3" and 7.3" to make tire height 14.6", and add in a 17" rim = 31.6"). Going to a 285/70/17 will be 0.8" wider, and 1.1" taller. Got it? Good. If not, go back and read the last paragraph again. When you understand the above paragraph, you can calculate any tire size.

If you don't know how to convert millimeters to inches, there are 25.4 millimeters in an inch.

Also, alignment settings on the front can alter fit quite a bit.

For this reason, the charts below are just a starting point, especially if you are planning a size much wider than 12". If you are planning on running a big tire with not a lot of modifications, a fit test is essential. Find a tire and wheel dealer that will let you do a test fit without commitment.

Here is a link to a metric to inch tire size converter. (don't buy Jeep wheels - the bolt pattern is not correct)

I'm going to continue editing my posts in this thread, adding more useful information and editing for clarity.
 

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Discussion Starter #2
Chart 1: 31" diameter. Will fit a completely stock FJ.
 

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Chart 2: 32" diameter. Might fit a stock FJ with no BMC. Definitely will fit with a BMC.
 

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Chart 3: 33" Diameter tires. Will not fit a stock FJ. BMC is mandatory. 1" - 2" lift recommended.
 

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Chart 4: 34" diameter tires. BMC mandatory. 2" - 3" lift at a minimum. Will probably need wheel spacers.
 

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Chart 5: 35" diameter tires. BMC mandatory. 2"+ lift mandatory. Wheel spacers recommended. LT suspension might be necessary. Body trimming and/or hammer work might be necessary.

More complications with larger tires: at 35" diameter, you should start looking at re-gearing your diffs to a lower gear (numerically higher). 2007-2008-2009 vehicles may experience decreased reliability at the differentials, due to the increased load on the ring and pinion. Just Differentials summed it up nicely:
The 2009 & Older FJ Cruisers utilize the 8” (diff) which dates back to 1979, and was originally used in 3000 lb mini trucks with 80 Horsepower and 27” tires. Late model modified Toyotas such as FJ Cruiser run at double the weight, triple the horsepower, and much larger tires to top it off. For this reason there have been lots of failures, enough so that Toyota upgraded the rear to the 8.2” on the 2010 & Newer models. It may seem like a small upgrade but there are significant improvements such as beefier casting, larger bearings, larger pinion diameter, larger ring gear diameter, more tooth contact, and a beefier 12 bolt diff case.
Any tires larger than 35" in diameter should be used with a solid axle swap, as Toyota's Hi-Trac IFS is not designed for tires of this size.
 

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Thanks for putting this together! I currently have 285/75/16 Duratracs. I have a 3" lift and a BMC. I'm basically looking to get the biggest tires that I can fit without any rubbing issues when I replace these in a year or so. Do you think a 315/75/16 would fit with my setup?

Edit: looks like you posted a few more charts while I was posting this. Sounds like they would fit, but I might need to get spacers. I have the TRD wheels right now.
 

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So would a 34" tire fit with a 3" lift, a BMC and 16" TRD wheels? I think it will, but I'm unsure on if I would need to get spacers or not.
 

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Can you do one for pizza cutters? I think I want to go for that old school look on my next sneaker purchase.
If you are unable to read posts #1, #2, and #3 in this very thread, I am unable to help you further.
 

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OK let's assume you're not a nice person and let's also assume that I'm an idiot who doesn't understand your idiots guide, can by you please explain like I'm five?
 

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OK let's assume you're not a nice person and let's also assume that I'm an idiot who doesn't understand your idiots guide, can by you please explain like I'm five?
^

As a member of this forum who knows how much effort it took for VK to create all of this and post it.........

Don't be a dick !!!!
 

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I think the one thing that will be UNDER APPRECIATED in this thread is how much time and effort it takes to make this kind of information available in a glance.
This is not a 15 minute posting... Not only have many of the common tire sizes been provided for multiple wheel sizes but the method of calculation and conversion has been provided allowing someone willing to do some work to determine a tire size on their own.
Great job VK.
 

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OK let's assume you're not a nice person and let's also assume that I'm an idiot who doesn't understand your idiots guide, can by you please explain like I'm five?
Take a look at post #1 - particularly ASPECT RATIO. Click the links, and really understand the concept of aspect ratio, as it relates to wheel size and tread width.

In a Metric tire size, all three numbers are interrelated. You need to understand the concept before you can figure out what size tire you want to run.

I've even put how to do the math in the first post.

All the information is there - it's not rocket science to figure it out.

Do this:
1) What size rims do I have?
2) How tall of a tire do I want?​

Everything else is dependent upon your answers to the first two questions.

"Pizza Cutter" sizes are already listed above.
 

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Take a look at post #1 - particularly ASPECT RATIO. Click the links, and really understand the concept of aspect ratio, as it relates to wheel size and tread width.

In a P-Metric or Euro-Metric tire size, all three numbers are interrelated. You need to understand the concept before you can figure out what size tire you want to run.

All the information is there - it's not rocket science to figure it out.

Do this:
1) What size rims do I have?
2) How tall of a tire do I want?​

Everything else is dependent upon your answers to the first two questions.

"Pizza Cutter" sizes are already listed above.
Gracias amigo. I meant no offense, as I'm sure neither did you. Some of the technical math aspects of this stuff totally fly over my head. I can't tell you how many times I've googled "understanding tire sizes" but it doesn't really help. :crying

It's all good, I have other talents, understanding math is just not one of them.

Thanks for putting this all together.
 

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Gracias amigo. I meant no offense, as I'm sure neither did you. Some of the technical math aspects of this stuff totally fly over my head. I can't tell you how many times I've googled "understanding tire sizes" but it doesn't really help. :crying

It's all good, I have other talents, understanding math is just not one of them.

Thanks for putting this all together.
Hint: look at tires with an 80- or 85-aspect ratio. Tall and skinny.
 
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