right now i am running a 315/75/16, i am about to change my rims to 18s and was wondering if a 305/70/18 would fit fine. i really know nothing about tire sizes or how they work. so anyhelp is appreciated. thanks in advance.

 

That tire is about the same diameter and width as your current tire.


What's important for fitting is to make correct choices on the wheels.
You need to get the correct backspace number. That determines where the tire sits.

You want to stay near the factory number of 5.75". Any more, you'll rub on the brake calipers or A-arm. Any less and you will stick out more and have rubbing issues on the fenders.

 

What Bunger said... But, if you plan on utilizing your Hummer off road, it would be best to stick with the 16's. More rubber, less rim...

 

the 18"s im getting are comming off a FJ cruiser.....i think he said the backspacing on them is 4.75....i will ask him later to double check and find out for sure. I work in the oilfield and most of my driving is highway with some nasty access roads from time to time but for the majority of them they are well kept. after nearly flipping my H3 while mudding I dont do much of that anymore lol

 

Backspace will be ok on those rims but your tires are going to stick out about an inch more on each side of the truck.

Make sure the center bore of those FJ rims are at least 101 mm diameter or they won't fit. H3's have a 100 mm center hub.

 

right on, i can live with them sticking out as that should do away with the wheel rubbing i have right now when i turn sharp. the center bore is 104 so i should be good. if you was buying the tires what size would you go with. i want to stick with the mastercraft courser mts or the mxt.

 

you can see the minimal difference here:

315/75-R16 vs 305/70-R18 Tire Comparison - Tire Size Calculator

 

I run 315/75/16 Goodyear Duratrac's. I refuse to run any bigger than a 16" wheel.
We do a lot of rock crawling around here with tires aired down to less than 20 lbs. so I want the most tire sidewall possible.

 

right on, but im trying to find the right tire for the rims im getting. i dont understand what the difference is, so whats the best tire size for me.

 

I run 295/70/18s, and I wheel all the time and I have no problems.

the difference is the 305/70/18s are a tad bit taller than your current ones