Originally Posted By drobs:
The next size up would be a 275/65R18 = 32 inch tire. Then 285/75R18 = 33 inch tire.

I ran 33 inch tires on 17 inch rims on my Toyota 4Runner and Jeep Willys for a long time. I now have 35 inch tires on my Jeep.

I would think you could get a 32 inch tire 275/65R18 on there pretty easily though.

You might join a Ford Explorer Forum and see what the largest tire sizes people are getting on them. I would guess a 33 with some trimming or pushing of the wheel liner.

Originally Posted By tarheel7734:

If I'm wanting a higher sidewall and more aggressive tread, wouldn't that be the second number? Ie something like a 265/75r-18 or 265/70-r18?

Originally Posted By VVinci:
The real problem is that you are changing your effective gearing. This may make your stability control and other things all wonky, it may just mess up your speedo and MPG readouts. There should be someone out there on an Explorer forum who knows. You might be able to fix all of this with a tune. Or maybe not. It is harder to tell with new cars with every passing year until someone does it and reports back.

The other thing you are doing that many people miss is that you are changing the reflected inertia of the vehicle to the driveline by effectively changing your overall gearing. Sometimes, this does nothing perceptible for durability within reasonable bounds of tire sizes. But, Jeepers can tell you many stories of broken parts with upsized tires when they went too far without changing axle ratios (higher numerically) to match taller tires. The T-5 in the old CJs, already not the world's strongest transmission, got an unfair rap for breaking a lot with big tires because people were too cheap/lazy/uninformed about the necessity of changes to axle ratios. That's what reflected inertia can do to a driveline.

How much margin for extra twist does an Explorer have in its driveline? IDK, but you can bet in today's CAFE-driven world where every gram of weight and every Watt of lost energy matters, it doesn't have much, especially in comparison to more truck-like vehicles that are expected to see a harsher duty cycle. 99% of Explorer owners don't do any more than soft roading - dirt roads and the like.

I think you would be OK with one size up, maybe two, but you should do research on the risk you are taking.

Originally Posted By drobs:
I've never seen a new Explorer off road. Does it have 4wd low? I don't think it does. The limited slip rear is neat but without 4low it's kind worthless. 4wd low keeps everything cool plus allows you to use your gearing for climbing things and going down steep hills. Instead of using either lots of gas pedal or brakes in 4wd high. 4wd low in most vehicles turns off traction / stability control.

Not trying to be a dick but If I were you and wanted to go off road, I'd trade it in on a Ranger or Big Bronco if you want to stay with Ford. Otherwise for midsize vehicles - Jeep Wrangler, Toyota Tacoma, 4Runner, or Land Cruiser, Nissan Frontier, or Chevy Colorado. All of which have 4wd low and lockers or limited slips available. Full size pickups and SUV's with 4wd low will work but will really get scratched.  

I've been on a bunch of trail rides where someone was struggling climbing over a simple rock ledge because they were in 4 high. I now can hear them revving the shit out of their vehicle. Just a couple weeks ago I had a guy in newer Colorado on my trail ride call over the radio saying he was overheating. My response "Are you in 4 low? If not you should've been 3 hours ago." He was in 4 high, switched to 4 low and had no issues from then on.

Originally Posted By tarheel7734:

My shoulders are too wide for a Ranger , Bronco or Colorado. I was looking at them before I got the explorer. I have not had a chance to look at a 4 runner yet as there have not been any available in trd when I was looking.

That being said my explorer has a couple hill modes.