How To Run 37’s On The Jeep Wrangler Rubicon JL
The 2018 to current Jeep Wrangler Rubicon JL has absolutely massive wheelwells. This makes squeezing on larger tires extremely easy. While Jeep is finally offering 35’s direct from the factory, we are still trying to understand why a 37-inch-tall tire is not an option. Given it comes standard on the Ford Bronco Raptor, one would think Jeep too would equip its most off-road capable platform with the taller rubber as well.
Thankfully, it doesn’t take much to run a true-to-size 37-inch-tall tire on the Rubicon platform. In fact, in some cases it can be done by simply changing out a single bumpstop (more on that in a minute). So, what do you actually need to run a 37-inch-tall-tire on the Jeep Wrangler Rubicon? Read on to find out.
Rubicon Flare
One of the biggest reasons you are able to run a 37-inch-tall tire so easily on the Jeep Wrangler Rubicon is due to the fact that the Rubicon models come equipped with highline flares. This flare design offers approximately two inches of additional clearance over the standard flare.
Bumpstops
The size of the suspension lift you choose doesn’t determine if you can properly cycle a 37, the bumpstops do. Bumpstops control the suspension up travel. By adding an additional bumpstop landing pad atop the axle, you are able to limit the up travel of the suspension. This is necessary to keep the tire from traveling too far into the wheelwell.
How Much Bump?
To properly cycle a true-to-size 37-inch-tall tire (such as the 37x12.50R17 Nitto Trail Grappler shown here), you need a minimum of two-inches of bumpstop. This means you will need to add a two-inch bumpstop landing pad on both the front and rear axle.
Backspacing
Just as important as the bumpstops is your Jeep’s wheel backspacing. From the factory, the standard Rubicon has appx 6 inches of backspacing and the XR wheels have 5.2 inches. Higher numerical backspacing keeps the tires tucked under the flare. As you move to a lower numerical backspace, the tire will poke farther out from under the flare. This can result in the tire rubbing on the fender. Staying with a wheel with 4.75 inches of backspacing and higher will help minimize rubbing when using a 2 inch bumpstop.
Rubbing
Even with two inches of bumpstop, you may find that your tires still rub the plastic liner on the inside of the wheelwell. Much of this will depend on your suspension travel and wheel backspacing. Thankfully, the most common rub point is at the backside of the rear inner fender. You can quickly and easily cut off with a razor blade the lower portion of the plastic that rubs.
No Cuts
If the thought of rubbing plastic bothers you, increasing the amount of bumpstop will prevent this from happening. Adding in an additional ½ or 1-inch of bump should eliminate the tire from contacting, though wheel backspacing and suspension travel will still impact this. Going with a taller bumpstop configuration will mean you are sacrificing up travel, which can impact ride quality and overall suspension performance.
Bumpstop Exceptions
If your JL Rubicon has a diesel engine or is a 392, the front bumpstop tower is already lower. This means you will not need to add an additional two-inch front bumpstop spacer on the front axle in order to run a 37. In fact, all you need on the Rubicon 392 is a two-inch rear bumpstop and you can run a 37 without issue. The setup you see here is a 37x12.50R17 Nitto Recon Grappler mounted on the factory Xtreme Recon wheel that has 5.2 inches of backspacing. Keep in mind that the Wrangler Rubicon 392 comes with a 2-inch suspension lift from the factory.
Lift Height Minimum
As we mentioned earlier, the amount of lift isn’t going to determine if the tire will rub, only the bumpstops. That being said, the least amount of lift you want to go with is 2 inches since you need to abbreviate the up travel by that amount. No matter if you opt for a 2 inch lift or a 4.5 inch lift, if the bumpstops are the same, the axle will stop at the same spot.
More From Driving Line
- 37's and No Lift? Watch this.
