The 2020 Jeep Gladiator has proven to be an excellent build platform for those looking to adventure off-road and maintain a useable midsized truck. But how far can you push it? Specifically, what’s the biggest tire size that will fit?

In this article, we’ll dive into everything you need to know about fitting massive 37″ tires on a Jeep Gladiator. We’ll look at whether it’s even possible with a stock suspension, what size lift kit and other upgrades are recommended, how it impacts fuel efficiency, and more.

By the end, you’ll know if transforming your Jeep Gladiator into an off-road monster with 37s is a pragmatic idea or just an over-the-top fantasy. Let’s hit the trail!

What is the Biggest Tire Size That Fits a Stock Jeep Gladiator?

The tires that come equipped on a Jeep Gladiator from the factory are:

• 255/75R17 on Sport and Sport S models
• 255/70R18 on Overland models
• LT285/70R17C on Rubicon models

With a stock suspension, the Gladiator has limited clearance and wheel wells to accommodate larger tires. Most owners find the biggest tire they can fit without any lift is approximately 33 to 34 inches in diameter.

Going much larger will result in rubbing against the fenders and other components during steering or suspension articulation.

So realistically, you’ll need to upgrade your Jeep with a lift kit in order to make the jump to massive 37 inch tires.

Do I Need a Lift Kit to Go to 37″ Tires on a Jeep Gladiator?

Yes, upgrading to 37″ tires on a Jeep Gladiator will definitely require installing a lift kit to make enough clearance.

Lift kits work by raising the suspension and body of the vehicle up higher above the axles. This creates space between the tires and surrounding parts of the truck for larger wheels and rubber.

Most experts recommend at least a 3 inch lift for safely running true 37″ tires without rubbing issues. A budget 2 inch lift might work with slightly smaller 37s, but it’s not ideal.

You’ll get better ground clearance and suspension geometry with a 4-6 inch kit. However, going above 3 inches may require additional modifications like a track bar relocation bracket.

There are a few options when it comes to lift kits:

• Suspension lift – raises just the suspension and not the body, minimal impact on alignment
• Body lift – spaces the body up off the frame, doesn’t affect suspension height
• Combination lift – lifts both suspension and body for maximum increase

An adjustable coilover suspension lift kit from quality brands like Rock Krawler or AEV is your best option. This will provide the right amount of lift while improving off-road performance.

Will 37″ Tires Fit on Stock Jeep Gladiator Wheels?

The stock wheels on a Jeep Gladiator range from 17″ to 18″ in diameter. They are too small in both size and width to properly fit 37 inch tires.

To safely mount massive 37″ tires, upgraded wheels in the 20″ to 22” range with 4.5” to 5” of backspacing are recommended. This provides the tire enough contact patch and stability.

Good wheel options that will clear 37s on a lifted Gladiator include:

• Fuel Hostage (20×9 with 4.5″ backspacing)
• XD Addict (20×10 with 5″ backspacing)
• Method 701 Trail Series (17×8.5 with 4.75″ backspacing)

The stock spare tire mount on the Gladiator can only hold up to a 35” tire at most. So you may need to relocate the spare mount when upgrading to 37 inch tires.

How Does a Lift Kit Affect the Jeep Gladiator Suspension?

Installing a lift kit allows you to run larger 37” tires on a Jeep Gladiator, but it also impacts the suspension performance:

• The altered suspension geometry from a lift gives increased articulation and wheel travel for better off-road capability.
• However, it can worsen ride quality on pavement and cause bump steer if suspension alignment isn’t addressed.
• A higher center of gravity also decreases stability and increases risk of rollovers.

To correct any issues after lifting, an alignment and adjustments to the track bar, control arms, and/or sway bar should be performed by a qualified shop.

High quality lift kits come with the required adjustable components for realigning the suspension. Upgraded adjustable control arms can also be installed to maximize performance.

What is the Best Lift Height for 37″ Tires on a Jeep Gladiator?

As mentioned earlier, a 3 inch lift is about the minimum needed to run 37 inch tires without major rubbing or clearance issues.

With a budget 2 inch lift, you may only be able to fit slightly smaller 37s in the 35-36 inch range. While better than stock, the ground clearance and suspension geometry benefits will be limited.

Stepping up to a 4, 5, or 6 inch lift kit allows safely clearing true 37″ or even larger tires. The greater height also increases axle clearance and improves off-road articulation.

But lifts over 3 inches can require more supporting modifications, put strain on CV axles, and cause excessive body roll. Not to mention worse fuel economy and on-road manners.

For most Gladiator owners, a 3 inch suspension lift paired with 1-2 inch body spacers is the best compromise. This provides enough height for unrestricted 37 inch tires, while minimizing drawbacks.

Do I Need Other Upgrades With a 37″ Tire Upgrade?

Along with a quality lift kit, upgrading to massive 37 inch tires on a Jeep Gladiator may require other modifications:

• Drivetrain – A gear swap to 4.56 or 4.88 ratios maintains power and traction.
• Brakes – Larger rotors and calipers improve braking for the increased wheel weight.
• Fenders – Trimming inner plastic can provide extra tire clearance.
• Bump stops – Extended bumps prevent over-extending the suspension.
• Wheels – As mentioned earlier, wider 20-22” wheels are needed for stability.
• Speedometer calibrator – Corrects speed readout for the larger overall tire diameter.

Not all of these are mandatory, but they allow your lifted Gladiator to perform properly with massive 37 inch tires. Consulting a qualified mechanic is recommended when upgrading.

Will 37″ Tires Reduce Gas Mileage on a Jeep Gladiator?

Yes, upgrading to larger 37 inch tires will negatively impact fuel efficiency on a Jeep Gladiator. Stock models with their original 255/75R17 or 255/70R18 tires achieve up to 22 mpg highway.

With proper gear ratios, you can expect a decrease of around 15-20% in MPG after switching to 37s. That puts realistic fuel economy in the 18-19 mpg highway range.

The specific reduction will depend on the tire brand, tread pattern, inflation level, and driving habits. Installing a lift kit also adds weight and aero drag that lowers MPG further.

Properly inflating your 37 inch tires and keeping them balanced can help recoup 1-2 mpg. But a sizable hit in fuel economy is unavoidable when going so large. Make sure to account for increased fuel costs.

How to Install 37″ Tires on a Lifted Jeep Gladiator?

Once you have your Jeep Gladiator lifted with upgraded wheels, follow this process to mount massive new 37” tires:

1. Remove the existing wheels and tires from the vehicle using a jack and lug wrench.
2. Inspect each new wheel closely and clean the mounting surface.
3. Apply a tire lubricant paste to the tire bead and wheel to prevent damage during mounting.
4. Using a tire mounting machine, mount the new 37 inch tires onto the wheels. Inflate to proper PSI.
5. Balance each new wheel and tire assembly to prevent vibrations at speed.
6. Mount the new assemblies on the Gladiator and torque the lugs to spec (140 ft-lbs).
7. Have your speedometer recalibrated by your dealer or installation shop to account for the larger overall diameter.
8. Perform a vehicle alignment to correct any suspension changes from the lift kit.
9. Do a test drive and full vehicle inspection to check for proper clearance, steering, and acceleration. Enjoy your lifted Gladiator with massive new 37s!

The Best 37″ Tire Options for a Jeep Gladiator

Ready to transform your Jeep Gladiator into a legitimate off-road beast? Here are some top-rated 37 inch tire options to consider:

BFGoodrich KM3: An ultra-rugged mud terrain tire with sidewall guards, great for rocks. Aggressive tread provides traction in mud. Downside is increased road noise.

Toyo Open Country M/T: Excellent all-around 37 inch tire choice that balances traction, low noise, and tread life. Deep tread lugs give good mud performance.

Nitto Trail Grappler: Hybrid tread combines off-road capability with quiet highway manners. Stone ejectors resist damage. Reasonably priced.

Goodyear Wrangler MT/R: Features Kevlar reinforcement and durable, self-cleaning tread. Excellent wet traction but only average life expectancy.

Falken WildPeak A/T3W: Impressive all terrain option that handles well on-road but still tackles off-road conditions. 65k mile tread warranty. Not the cheapest.

Consulting tire experts and other Jeep Gladiator owners can help narrow options further. Shop around for the best deals once you’ve selected the right 37” set.

Conclusion

• A 3-4” lift kit is mandatory to fit 37” tires without rubbing on a Jeep Gladiator
• Upgraded wheels, drivetrain modifications, and recalibration required
• Expect around a 20% reduction in fuel economy
• Multiple rugged all-terrain and mud-terrain options available
• With right upgrades, 37s transform Gladiator into off-road monster

So is running true 37″ tires on a Jeep Gladiator a crazy idea? Provided you install the proper lift kit, wheels, and supporting mods, it’s very doable. Just be ready for the compromises in ride quality, mpg, and cost. But if maximizing your Gladiator’s off-road performance is the priority, 37s can be well worth it!