Running 37's on a Stock JL Rubicon: Is It Possible?

You Can Run 37s on a Stock JL Rubicon.

The Jeep Wrangler Rubicon JL, produced from 2018 to now, features exceptionally large wheelwells, allowing for easy installation of larger size tires.

While Jeep now offers 35-inch tires straight from the factory, it remains puzzling why 37-inch tires aren’t available as an option. Since the Ford Bronco Raptor comes standard with these larger tires, it seems logical that Jeep would also provide them for its top off-road model.

Highline Flares

A key reason you can easily fit a 37-inch tire on the Jeep Wrangler Rubicon is the highline flares that come standard on Rubicon models. These flares provide about two extra inches of clearance compared to regular flares.

Bumpstops

The size of the suspension lift you select does not determine whether you can effectively use a 37-inch tire; that responsibility falls to the bumpstops. Bumpstops manage how far the suspension can move upward. By adding an extra bumpstop landing pad on top of the axle, you can restrict the upward movement of the suspension. This step is essential to prevent the tire from going too far into the wheelwell.

A minimum of two inches of bumpstop is required to correctly cycle a true-to-size 37-inch-tall tire. This implies that the front and rear axles will require the addition of a two-inch bumpstop landing pad.

The wheel backspacing on your Jeep is equally crucial to the bumpstops. The stock backspacing for the normal Rubicon is around 6 inches, while the factory XR wheels have 5.2 inches. The tires are kept tucked under the flare by higher numerical backspacing. The tire will poke out further from under the flare when you backspace to a lower number. The tire may rub against the fender as a result of this. When employing a 2 inch bumpstop, sticking with a wheel that has 4.75 inches of backspacing or more will assist reduce rubbing.

Backspacing

The wheel backspacing on your Jeep is just as important as the bumpstops. The stock backspacing for the normal Rubicon is around 6 inches, while the factory XR wheels have 5.2 inches. Higher numerical backspacing keeps the tires tucked under the flare. The tire will poke out further from under the flare when the backspacing is a lower number. The tire may rub against the fender as a result of this. When employing a 2 inch bumpstop, sticking with a wheel that has 4.75 inches of backspacing or more will assist reduce rubbing.

Rubbing

You may find that your tires continue to rub against the plastic liner inside the wheelwell even with two inches of bumpstop. Wheel backspacing and suspension travel will play a big part in this. Fortunately, the rear inner fender’s backside is the most frequently encountered rub site. With a razor blade, you may swiftly and easily cut off the rubbing piece of the plastic.

Increasing the amount of bumpstop will stop this from happening if the idea of rubbing plastic worries you. The tire should not come into touch with the additional ½ or 1-inch of bump; but, wheel backspacing and suspension travel will still affect this. You will give up some travel if you choose a taller bumpstop arrangement, which may affect the suspension’s overall performance and ride quality.

The wheel backspacing on your Jeep is just as important as the bumpstops. The stock backspacing for the normal Rubicon is around 6 inches, while the XR wheels have 5.2 inches. The tires are kept tucked under the flare by higher numerical backspacing. The tire will poke out further from under the flare when you backspace to a lower number. The tire may rub against the fender as a result of this. When employing a 2 inch bumpstop, sticking with a wheel that has 4.75 inches of backspacing or more will assist reduce rubbing.

Exceptions

The front bumpstop tower on a JL Rubicon with a diesel engine or a 392 model is already lowered. This implies that using a 37 will not require the insertion of a second two-inch front bumpstop spacer to the front axle. Actually, the only thing required to run a 37 on the Rubicon 392 is a two-inch rear bumpstop. Remember that the factory suspension lift on the Wrangler Rubicon 392 is 2 inches.

As I mentioned earlier, the bumpstops—not the amount of lift—will decide whether the tire will rub. Having said that, since you must shorten the upward trip by that amount, the lowest lift you should use is two inches. The axle will stop at the same location whether you choose a 2 inch or 4.5 inch lift since the bumpstops will remain the same.

Lift Height

As previously stated, the bumpstops—not the amount of lift—will decide whether the tire will rub. Having said that, It is still recommended to go with at least a 2 inch lift to reclaim the travel lost with a larger bump stop. The axle will stop at the same location whether you choose a 2 inch or 4.5 inch lift since the bumpstops will remain the same.