Need Some Tire Size Help

TheColter · October 16, 2009

Okay, I need some help here. I’m currently deployed in Iraq and I’m trying to get some information/advice on from some of the forum members here. The internet here is horrible and searching the forum just isn’t that pleasant of an experience.

I have a 2008 Z71 4X4 that currently has the Rough Country 2” leveling kit installed. I want to put a new wheel and tire combo on the truck with a slightly bigger tire. I’m looking at a 305/70R18 (32.6”x12.1”) Mickey Thompson Baja ATZ mounted on an 18x9 MotoMetal MO951 wheel. Now on to my questions…

Will the tire size I’m looking at clear with just the leveling kit?

Also, what backspacing / offset should I be looking for on the wheels? I don’t want anything sticking out further than it has to. It looks like my options for this wheel are:

Backspace: 4.53” / Offset: -12mm

Backspace: 5.71” / Offset: 18mm

Backspace: 6.18” / Offset: 30mm

I appreciate any help or suggestions!

Ron505 · October 16, 2009

First off, thank you for what you do.

Now, I have a 2" leveling kit with helper springs in the back, and the largest tire I could fit was a 305/60-18......and it still rubbed. I did a small modification to get it to clear. I too got 18"x9" wheels with 0 offset. Mine stick out maybe 1" past the fenders.

BTW, I like your choice of wheel and tire combo. Sounds killer!

TheColter · October 16, 2009

What type of modification did you have to make for proper fitment? trimming the plastic inner portion of the fender?

I've been doing some research and it seems like I would want to go with the 30mm offset wheels. That would extend 20mm (.8") to the outside of the the wheel and 18mm (.7") on the inside of the wheel as compared to the stock specs. Now, I'm wondering if that reduction of 18mm of clearance between the wheel and A-Arm / strut assembly would cause any clearance issues. I can't just run out and check how much clearance is present with the stock wheels at full lock, which sucks. But this would be the best option for minimizing how much the tires stick out beyond the fenders.

The instructions for the Tough Country leveling kit also states that you will need to go with a wheel offset of 30 or greater if you go with aftermarket wheels and 285/70R17 tires. So I'm thinking that's the route I need to go.

I'm still up for anyone's input based on experience.