Larger tires have long been a hallmark of Jeep customization, with 37-inch diameters representing a popular upgrade for serious off-roaders. However, the question of whether these massive tires are suitable for daily highway use remains hotly debated. This article provides detailed expert analysis of 37-inch tire performance on paved roads, covering everything from ride quality and safety to fuel economy and legal compliance.

Understanding 37-Inch Tire Characteristics

37-inch tires are typically classified as extreme off-road or mud-terrain (MT) designs. Their oversized dimensions and aggressive tread patterns deliver superior traction in loose dirt, rocks, and mud, but these same features create significant trade-offs on paved surfaces. To understand highway suitability, it helps to examine four core characteristics of these tires:

Tread Design and Rubber Compounds

Most 37-inch tires use deep, widely spaced lugs with large voids between tread blocks. This design is optimized for self-cleaning in mud and gripping rocks, but on asphalt the large tread blocks can squirm and deform, reducing contact patch stability. The rubber compounds in off-road tires are also harder and more heat-resistant to withstand rough terrain, but they do not provide the same grip as softer highway compounds when braking or cornering on wet pavement.

Weight and Rotational Inertia

A single 37-inch mud-terrain tire can weigh between 70 and 90 pounds, sometimes more. Combined with a heavy wheel, total corner weight may exceed 100 pounds. This dramatically increases unsprung mass and rotational inertia. Heavier wheels and tires make the suspension work harder to maintain contact with the road, resulting in a harsher ride and reduced responsiveness. The extra rotational mass also demands more power to accelerate and decelerate, straining drivetrain components.

Sidewall Construction

Off-road tires designed for 37-inch applications often feature reinforced sidewalls with multiple plies (E-rated load range) to resist punctures and sidewall cuts. While this adds durability for rock crawling, it also makes the tire stiffer laterally. On highways, a stiff sidewall transmits more road imperfections into the cabin and reduces the tire's ability to absorb small bumps, contributing to a rougher ride.

Rolling Resistance

The combination of heavy tread blocks, thick rubber, and aggressive tread pattern creates high rolling resistance. A 37-inch mud-terrain tire can have rolling resistance 20–30% higher than a comparable all-terrain or highway tire. This directly translates into lower fuel economy, additional heat generation, and accelerated wear when driven at highway speeds for long distances.

Expert Opinions on Highway Performance

Automotive engineers, off-road specialists, and experienced Jeep builders offer nuanced perspectives on running 37-inch tires on highways. Their consensus is that while it is technically possible, it requires careful consideration of several factors.

Handling and Stability

According to a Tire Rack technical article, larger diameter tires alter a vehicle's steering geometry and scrub radius. On a Jeep Wrangler or Gladiator, a 37-inch tire significantly changes the caster angle, which can lead to wandering or loose steering at highway speeds. Experts recommend adjustable control arms and a proper alignment to mitigate this. Even then, the vehicle's center of gravity rises, increasing body roll during lane changes and emergency maneuvers. Many off-road shops advise that a 2-inch or higher lift kit is mandatory to maintain safe suspension geometry with 37-inch tires.

Braking Performance

Stopping distance increases noticeably with 37-inch tires. The heavier wheel assembly requires more braking force to slow down, and the reduced contact patch (per square inch) can lead to longer stopping distances, especially on wet or slick roads. MotorTrend testing has shown that vehicles with oversized tires often require 10–15% more distance to stop from 60 mph compared to factory tire sizes. Upgrading to larger brake calipers and rotors is frequently recommended for safety.

Noise and Ride Comfort

All-terrain tires are noisy on the highway, but mud-terrain 37-inch tires are louder. The aggressive tread pattern produces a constant hum and drone at speeds above 50 mph. Many owners report that interior noise levels become fatiguing on long trips. Some premium mud-terrain tires, like the BFGoodrich KM3 or Toyo Open Country M/T, incorporate noise-reducing features such as variable pitch tread blocks and sound-absorbing foam, but they still produce more noise than highway tires. Experts suggest that drivers who frequently take 2+ hour highway trips may find the noise unacceptable.

Fuel Economy Impact

Fuel efficiency suffers markedly. A Jeep Wrangler equipped with 37-inch mud-terrain tires can see a drop of 3–5 mpg compared to stock tires. For a daily driver covering 15,000 miles per year at $3.50 per gallon, that translates to roughly $500–$900 in additional fuel costs annually. The added rolling resistance and aerodynamic drag (wider, taller tires increase frontal area) are primary culprits.

Vehicle Modifications Required for 37-Inch Tires

Running 37-inch tires on a Jeep requires significant modifications beyond simply bolting them on. These modifications directly affect highway safety and legality.

Lift Kit and Fender Clearance

Most Jeep Wrangler models (JK, JL, JT) need at least a 3-inch suspension lift to clear 37-inch tires without rubbing. This includes installing longer control arms, track bars, and bump stops. Inadequate lift can cause tire contact with the fenders, sway bars, or frame during turns or suspension compression, which is dangerous at highway speeds. Additionally, the increased ride height raises the vehicle's roll center, requiring upgraded sway bars to limit body lean.

Axle and Drivetrain Upgrades

The stock Dana 30 front axle and Dana 35/Dana 44 rear on older Jeeps may not handle the stress of 37-inch tires, especially with lockers or hard off-road use. Experts recommend upgrading to Dana 60 axles or at least chromoly axle shafts and stronger differential covers. The added weight and rotational mass also stress the transmission, transfer case, and driveshafts. Regearing the differentials to a lower ratio (e.g., 4.88 or 5.13) is essential to restore acceleration and keep the engine in its efficient RPM range. Without regearing, highway driving becomes sluggish, and the transmission may hunt for gears.

Speedometer and Gearing Calibration

A 37-inch tire has a circumference roughly 18% larger than a factory 32-inch tire. This means the vehicle's speedometer will read about 10–15% slower than actual speed unless recalibrated. Modern Jeeps (2018+ JL/JT) can be calibrated using a programmer such as the Superchips FlashCal or dealer-level scan tool. Failure to recalibrate can lead to inaccurate speed readings, transmission shift issues, and even ABS or stability control malfunctions.

Real-World Experiences from Owners

Online Jeep forums (e.g., JL Wrangler Forum, WranglerTJForum) are filled with firsthand accounts. Many owners who daily drive on 37-inch tires emphasize that it is doable but not ideal for everyone. A typical comment: "I've had 37" KM3s for two years. The looks and off-road capability are amazing, but you feel every bump, the highway drone gets old, and I lost about 4 mpg. I'd only recommend if you off-road at least once a month." Others mention that adding a high-quality lift, adjustable shocks, and upgrading the steering box greatly improved highway manners. Some owners have returned to 35-inch tires for daily use, citing comfort and cost.

Alternatives to 37-Inch Tires for Mixed Use

If highway performance is a significant priority, experts suggest considering alternatives that offer a better balance.

35-Inch Performance All-Terrain Tires

35-inch tires provide much of the off-road capability of 37s with substantially lower weight, rolling resistance, and required modifications. Modern all-terrain tires like the BFGoodrich KO2 or Falken Wildpeak AT3W offer excellent highway ride quality, reduced noise, and up to 50,000-mile treadwear warranties. They can fit most Jeeps with a 2.5–3 inch lift and minimal trimming, requiring less drivetrain regearing. The fuel economy penalty is typically only 1–2 mpg.

37-Inch All-Terrain Options

For those set on 37-inch diameter, all-terrain tires exist but are rare. The Falken Wildpeak AT3W in 37x12.5R17 is one example. These tires have less aggressive tread than mud-terrains, offering better highway comfort and lower noise while still providing decent off-road traction. However, they still require the same lift and gearing as mud-terrains. They are a compromise for frequent highway users who need 37s for clearance.

Hybrid Tire Designs

Brands like Toyo (Open Country R/T) and Goodyear (Wrangler Duratrac) offer "rugged terrain" tires that straddle the line between all-terrain and mud-terrain. They feature more aggressive sidewalls and tread than standard ATs but with smaller voids and variable pitch patterns that reduce highway noise. These are a good option for drivers who encounter moderate off-road conditions but still commute long distances.

Many regions have laws regarding tire protrusion beyond the fenders. Most states require tires to be fully covered or have mud flaps at a certain width. 37-inch tires often require aftermarket fender flares to comply. Additionally, some insurance policies may deny coverage for accidents involving modifications that affect safety (e.g., improper lift, inadequate brakes). It is wise to check with your insurance provider about coverage for large tires and lift kits.

Expert Recommendations

The final word from most Jeep builders and off-road experts: 37-inch tires are not optimal for a daily-driven highway Jeep. They are a dedicated off-road choice that can be made tolerable for highway use with extensive modifications and a willingness to accept compromises in comfort, fuel economy, and handling. If you rarely venture off paved roads, stick with 33–35 inch all-terrain tires. If you need 37s for serious off-roading, consider a second set of wheels and tires rated for highway use, or accept that the highway experience will be distinctly compromised.

For those determined to run 37-inch tires on the highway, the experts strongly advise: regear the axles, upgrade the brakes and steering, fit a proper lift with quality shocks, and always maintain proper tire pressure (typically 30–35 psi on-road). Regular tire rotations and alignments are critical to extend tire life. With these measures, a 37-inch tire can be used for mixed driving, but expectations should be managed.

Conclusion

Jeep 37-inch tires can be mounted and driven on highways, but the suitability depends heavily on your tolerance for noise, ride harshness, fuel costs, and safety trade-offs. Experts unanimously agree that they are not ideal for primary highway use without substantial vehicle modifications and performance sacrifices. For a daily driver that sees occasional trails, 33–35 inch tires are far more practical. However, if you are committed to the off-road capability of 37s and can accept the highway compromises, the technology and aftermarket support exist to make it work. As always, consult a trusted tire specialist and off-road shop to configure your Jeep for your specific driving mix.