37” vs 38” Nitto Trail Grapplers

• March 19, 2023
• Story By
  Ali Mansour

The modern Jeep Wrangler is absolutely massive compared to the original YJ that debuted 36 years ago. As the Wrangler platform continued to grow over the decades, so did the tires off-road enthusiasts put under it. During the late '80s and early '90s, the 33x12.50" reigned supreme. By the time the TJ launched in 1997, the 33 was already being phased out by the 35x12.50".

In 2007, we saw the birth of the four-door Wrangler Unlimited. This much longer wheelbase ushered in not only a more diverse Jeep buyer, but started the trend we still see today of running 37-inch-tall tires. With Jeep now offering 35-inch-tall tires direct from the factory with the Xtreme Recon package, the idea of moving up to a 37 isn’t radical. Much like the Wrangler four-door, the even longer Gladiator platform is creating the stage for the next evolution of tire upsizing with 38-inch-tall rubber.

Previous to the 38, if you wanted to run something taller than a 37, you had to make a huge leap to a 40-inch-tall tire. Sure, three inches doesn’t seem like a massive jump. However, history has shown us that the weight, traction potential, and sheer size of the 40 necessitates a tremendous amount of additional upgrades to the vehicle. The question now remains, is moving up to a 38 over a 37 worth it? That’s what we are going to focus on in this article.

The Contenders

To get a more apples to apples comparison, we are going to look at one of the most prominent mud-terrain radials on the market that is offered in both a 37 and 38- the Nitto Tire Trail Grappler. The 37x12.50R17 Nitto Trail Grappler has been around for over a decade. It’s a mainstay tire in the Jeep world. The 38x13.50R17 Trail Grappler however is fairly new.

True to Size

Looking at the same type of tire from the same manufacturer also give you an indicator of how true-to-size the tire will be. Virtually, no tire is sized exactly as the sidewall states, but Nitto’s are more closely aligned to that embossed number than others on the market. For example, the Trail Grappler in a 37x12.50R17 is listed as having an inflated diameter of 36.85 inches. For the 38x13.50R17, it’s 37.76 inches.

Weight Differences

The biggest thing we noticed when comparing the 38 to the 37 was that the 38 is only roughly 3 pounds heavier than the 37. That’s a big deal. This makes the move to taller tire less stressful on your powertrain. To put this in comparison, a jump from a 35 to a 37 can often add on up to 15 pounds per tire.

12.50 vs 13.50

The most common width for a 37-inch-tall tire is 12.50 inches. The 38-inch-tall Trail Grappler has a slightly wider 13.50-inch pattern. This added width is barely noticeable on-road but will be a benefit on the trail. The only real downside to the 13.50 is that at lower air pressure, you will increase the footprint and create more strain for the vehicle's steering system.

Load Capacity

Both the 38 and 37 come with an 8-ply, Load Range D sidewall. So, you are getting Nitto’s nearly indestructible sidewall with either option. The main difference here is that the 37 is rated for 330 pounds of additional load capacity over the 38. Considering the 38 still boasts a max-load capacity of 3,195 pounds at 50 PSI, it’s more than enough for even a portly Gladiator or Wrangler build (overlanders, we’re looking at you.)

Pricing Difference

As we are writing this, there’s approximately a $40 retail difference between the 37 and 38. That’s an extra 200 cold ones for a set of five. How much that makes a difference to you will depend on your budget.

Other Considerations

No matter which tire is right for you, the move to a 37 or 38 is going to require a host of other upgrades to your Wrangler or Gladiator. While we discuss these more in our latest video (Watch Here), the four biggest areas you’ll need to address are suspension, differential gearing, spare tire placement, and axle upgrades. A 38-inch-tall tire is definitely pushing the limits of what the stock axles can handle. If you are easy on the gas pedal off-road and make smart line choices, you may be able to run these for years without issue. The third generation Dana 44 axles are very impressive overall.  

Our Choice

After considering all of our options, we ultimately decided to take a chance on the larger 38x13.50R17 Nitto Trail Grappler for our 2020 Jeep Gladiator Rubicon. For the longer wheelbase of the JT, we feel it’s a better fit for the Gladiator and not as dramatic of a jump as 40. We mounted ours on a 17x8.5 Method 701 Bead Grip wheel in a matte black finish. The wheel has a zero offset and 4.75 inches of backspacing. This gives us plenty of suspension clearance, without completely zapping our scrub radius. While we are at the top end of what we feel as though our Rubicon axles can handle, we believe that with smart driving, we can make this setup last.