37’s and No Lift Jeep Wrangler Unlimited Rubicon 392 Xtreme Recon
We always want more. No matter what it is. It’s basic human nature. When Jeep launched the Xtreme Recon package, it marked the first time in the Wrangler’s long history that the open-top wheeler would come with 35-inch-tall tires direct from the factory. Couple that with the fact you could get this package with the pavement-ripping V8 and you have the makings of the most capable Jeep ever produced.
Admittedly, we were fairly content when we first picked up our 2021 Jeep Wrangler Unlimited Rubicon 392 with the Xtreme Recon package in December of last year. After waiting over five months for it to get delivered, we were just happy to finally get behind the wheel. While we’ve done a few upgrades to the Jeep since purchasing the JL, the one thing we’ve wanted to do, but haven’t, is find out if a 37-inch-tall tire would work. By "work" we mean not require any modification to properly cycle off-road.
You can actually watch us put this to test on our Inside Line video series on YouTube. Here, we’ve put together a few highlights for anyone curious about the same upgrade.
To test out our 37’s and no lift theory we deiced to use a set of tires and wheels that were ideally suited for our experiment. The tire is a 37x12.50R17 Nitto Trail Grappler. It’s a mud-terrain radial that we’ve had plenty of experience with in the past. Most importantly for this test, it’s a very true-to-size 37 measuring in at 36.85 inches.
Just as important as running a true-to-size tire, we wanted a wheel with a high-amount of backspacing. That’s why we are using an AEV Borah DualSport beadlock wheel. This would do a few things. First, it would mimic the factory specs more closely. So, if you are thinking about trying this on the stock 17-inch beadlock capable wheels, this article will be more applicable. Second, going with a high backspacing figure (in this case 5.72 inches) keeps the scrub radius down, which makes a tremendous impact on the handling of the Jeep.
Our 17x8.5-inch AEV wheel is configured in the true beadlock configuration and has +25mm of offset. This keeps the tire tucked under the fender similar to how it came from the factory. The result is less debris slinging on the side of the Jeep and a tire that cycles more easily under the flare.
Rather than searching out a random ditch to flex the Jeep, we decided to go with a slightly more unusual, but extremely effective flex solution. By pulling our Jeep on top of our S-10’s 40-inch-tall Mud Grappler, we could force the suspension to full cycle and collapse the bumpstops.
We’ve tested 37’s and no lift on the Jeep Gladiator Rubicon platform in the past and had a good idea how much wheelwell we had to work with in regards to completely stuffing a true-to-size 37-inch-tall tire. The main difference here is that the 392 comes from the factory with around 2 inches of lift. To moderate this suspension travel, the bumpstop perch on the chassis side was extended at the factory. Even with the bump fully collapsed, we found we had plenty of room up front for the 37’s to roam. It’s also worth noting that we were clear of the lower control arms and front bumper.
Rear’s The Problem
With so much room up front, we were optimistic about what we would find out back. Unfortunately, we quickly found that it does rub considerably on the plastic inner liner and even a little on the bottom side of the main flare. Is it enough to damage or tear off the fender on the trail? Possibly. Given how pricy these painted flares are to replace, it’s not something we would want to risk. If the wheel had less backspacing, this issue would be much worse. Our wheel set is best case scenario for sure.
Our 392 came with a 1-inch bumpstop placed on the rear axle from the factory. In our experience, a two-inch bump is needed to cycle a 37 outback on the JL platform. Even then, you may find you’ll need to do some small plastic trimming. Ultimately, a quick fix would be adding a taller bumpstop. However, we’ve found there is more that this stock suspension is lacking. More on that in a minute.
The Xtreme Recon comes with the Mopar tailgate reinforcement and relocation bracket that moves the spare to a higher position. The good news is a 37 will fit back here without issue. The only modification we had to make was to move up the stock third brake light. All this required was unbolting the light mount and simply moving it up where it only uses one set of bolts to hold the light tower. An easy two-minute modification.
35’s vs. 37’s
We had previously been running a 35x12.50R17 Nitto Ridge Grappler on a 17-inch AEV Pintler wheel. That setup weighed in around 110 pounds. The 37-inch Trail Grappler on the AEV Beadlock is around 8 pounds heavier. Given the power of the 392, and the fact that it comes with 4.56 differential gears, we haven’t noticed a major difference. Fuel economy seems to be close to the same and using the Tazer to put the Jeep into 2WD, we can easily roast the 37’s on command. If anything, the 37’s have helped calm the RPM’s on the highway, which should actually help with the fuel economy on longer trips. Steering and braking seem to be close to the same, though we are anxious to get the Jeep on some real trails to see how the steering feels with the larger treads aired down.
If you are going to do very light wheeling and extreme mall crawling, this setup works perfectly fine. For us, we can’t unsee the 37’s on the Jeep, so we feel this is definitely the direction we want to go. The main challenge we’ve found with our suspension has to more with the shortcomings up front. The suspension tends to top out (run out of downwards travel) and have difficulty at speed of controlling the heavy weight of the V8 engine off-road. We like the low lift, big tire setup. So, we’re hoping that someone in the aftermarket will offer a 2-to-2.5-inch lift that will allow us to retain the ride height the Jeep has but increase the suspension travel and dampening power.
More From Driving Line
- Looking for a 2-inch lift for your JL? Check out this setup!