I want to put Pro Comp 18" by 9" series 7005 wheels on my FX4.

I wan't Nitto 33" tires but dont understand the sizing (like 305/40/18) ect....

What size do I order to fit my wheels and be 33" tall tires?

 

Check this out

http://www.miata.net/garage/tirecalc.html

Diameter is shown.

 

either the 325/60/18 with is a d range load

or the 285/65/18 which are a tad shorter but e range

problem is you have to look at the rim width make sure you get the correct tire for that rim width

 

With tire sizes, the first number is the width of the tire in millimeters.
The second number is the aspect ratio - percentage of the width that is the sidewall.
The third number is the rim diameter in inches.

My new tires are 295/70/17. That means they are 295mm wide (roughly 11.5"), 70% of the width is the height of the sidewall (a little over 8"), and that they are sized for a 17" rim.

Hope that helps a little.

 

Here's a pretty good website/calculator that might help you to visualize metric tire sizing.

http://www.bigcustomwheels.com/rt_specs.jsp

Taking your example (305/40-18):
The 305 (in millimeters) is the width of the tire at its widest point. This means the bulge, not tread width.
The 40 is the aspect ratio (a percentage), a way to denote the sidewall height. Basically 40% of 305mm = sidewall height (wheel to tread).
The 18 is the wheel diameter.

So...305mm is the width (12.0"), sidewalls are 0.4*305mm = 122mm (4.8"), and wheel diameter is 18".

4.8" + 18" + 4.8" = 27.6"
You've got a 27.6" x 12" R18 tire in standard sizing. Kind of an odd size , but the math works out the same for more common sizes.

Edit: I need to learn to type faster...three replies in the time it took to write mine...sheesh.

 

so would 305/65/18 be a good proportioned tire for a fx4 with a 2.5" lift? (about 33.6"'s tall)

 

That is an excellent size tire for a leveled 4x4, they can fit on the stock wheels or certain size aftermarket wheels.