Upgrading to 37-inch tires on your Jeep is one of the most impactful modifications you can make, dramatically transforming its off-road prowess, ground clearance, and aggressive stance. However, this upgrade is far from a simple tire swap. It involves a cascade of compatibility considerations, significant costs, and necessary supporting modifications that can make or break your experience. Whether you drive a Wrangler JL, a Gladiator, or an older JK, understanding what it takes to run 37s—from suspension lifts and re-gearing to wheel offset and brake upgrades—is essential before you spend a dime. This comprehensive guide covers everything you need to know about compatibility, costs, and long-term ownership so you can plan your build with confidence.

Understanding Compatibility: More Than Just Clearance

Slapping 37-inch tires onto a stock Jeep is rarely a viable option. These tires are roughly 6-7 inches taller than factory 31-33 inch tires, which affects almost every aspect of your vehicle’s geometry and drivetrain. Compatibility extends far beyond clearing the fender wells.

Suspension Lift Requirements

For most Jeep Wrangler and Gladiator models, a suspension lift is mandatory when stepping up to 37-inch tires. The lift provides the necessary spring and shock travel to prevent tires from contacting the body, fenders, and suspension components at full articulation. The typical lift height for 37s ranges from 2.5 to 4 inches, depending on the Jeep generation and wheel setup.

  • JK (Wrangler 2007-2018): A 2.5-inch lift with proper bump stops often clears 37s, but trimming the front lower control arm brackets and using flat fenders may still be required.
  • JL (Wrangler 2018+) and JT (Gladiator): A 2.5‑3.5 inch lift is the sweet spot. Higher clearance helps with full flex, but excessive lift can introduce driveline vibrations and poor handling.
  • Lift Type: Coil spring lifts with adjustable control arms are preferred for optimal geometry. Budget spacer lifts might work on pavement but will limit articulation and ride quality off-road.

It is crucial to consider your suspension type—long-arm vs. short-arm—because long-arm kits offer better ride quality and articulation but are more expensive and labor-intensive to install.

Wheel Size, Offset, and Backspacing

Wheel choice directly affects how 37-inch tires fit. The most common wheel diameters for 37s are 17 and 18 inches. 17-inch wheels are favored for off-road driving because they allow more sidewall flex for airing down, which improves traction on rocks and sand.

  • Width: An 8.5 to 9.0 inch wide wheel is ideal. Too narrow and the tire bead may unseat; too wide and the tire’s sidewall becomes vulnerable to damage.
  • Offset and Backspacing: Negative offset (more aggressive) pushes the tire outward, increasing stability but also placing more stress on steering components and bearings. For JK/JL/JT, a 4.5 to 4.75 inches of backspacing (or 0 to -12 offset) is typical for 37-inch tires to avoid rubbing on the frame or suspension at full lock. However, this often requires aftermarket fender flares for legal coverage.

Avoid using wheel spacers to correct offset on a stock wheel; they increase the risk of lug nut failure and can cause premature wheel bearing wear. Invest in properly spec’d wheels from the start.

Re‑gearing and Performance

One of the most overlooked aspects of the 37-inch upgrade is the effect on your Jeep’s effective gear ratio. Larger tires multiply the final drive ratio, which means your engine has to work harder to maintain the same speed. The result is sluggish acceleration, loss of towing capacity, and transmission hunting for gears.

  • Ideal Gear Ratios: For a 3.6L Pentastar (JK/JL/JT), 4.88 or 5.13 gears are recommended for 37-inch tires to restore near-stock driving performance. Diesel owners (EcoDiesel) can often get away with 4.10 or 4.56 gears due to higher torque.
  • Transmission Considerations: The 8-speed automatic in JL/JT (850RE) shifts more efficiently than the older 5-speed (42RLE in TJ) or 6-speed manuals, but it still benefits from re-gearing. Overdrive can become unusable without proper gear set.
  • Speedometer Calibration: Larger tires throw off your speedometer and odometer. A tuner (like Superchips Flashcal or Tazer JL Mini) will re-calibrate and also allow you to adjust shift points.

Re-gearing costs between $1,200 and $2,000 per axle, depending on whether you use aftermarket lockers at the same time. This is one of the largest hidden expenses of running 37s.

Fender Trimming, Bump Stops, and Body Modification

Even with a lift, 37s can still rub during extreme flex. Trimming the factory fenders or installing aftermarket flat fenders (like Metalcloak or Poison Spyder) creates extra clearance. Adjusting bump stops is critical—without them, the tire can contact the fender at full compression and cause damage. Many off-roaders also remove or relocate the front sway bar disconnect links to prevent binding.

If you are on a budget, you may be able to fit 37s with only a modest lift by aggressively trimming the pinch welds and inner fender liners, but this approach compromises aesthetics and resale value.

Cost Considerations: Budget for the Whole Package

The sticker price for a set of 37-inch tires ranges from $1,200 to $2,500, but that is just the tip of the iceberg. A complete 37-inch build typically costs $5,000 to $12,000, depending on the quality of components and whether you do the labor yourself.

Detailed Cost Breakdown

  • Tires: All-terrain tires (e.g., BFGoodrich KO2, Nitto Ridge Grappler) run $350–$500 each. Mud-terrain tires (Toyo Open Country M/T, Cooper STT Pro) are $400–$600 each. Load range matters: at least Load Range C (if available) for Jeep weight, but many 37s are Load Range D or E, which are heavier and harm ride quality.
  • Wheels: Steel wheels start at $100 each, while quality aluminum beadlock-capable wheels like Methods or KMCs range from $250 to $500 each. Five wheels (including spare) adds $500–$2,500.
  • Suspension Lift: Budget lifts (springs + shocks) cost $800–$1,500. Mid-range kits ($1,500–$2,500) include adjustable control arms and better shocks (Fox, Bilstein). High-end long-arm kits run $3,000–$4,500.
  • Re‑gearing: Parts and labor for front and rear differentials: $1,200–$2,500 depending on ring and pinion brand (Yukon, Revolution) and lockers.
  • Speedometer Calibrator: $200–$300 for a Tazer or similar tool.
  • Alignment and Installation: Professional installation costs $400–$800 for mounting, balancing, and a four-wheel alignment. If you also need re-gearing, expect at least $1,000 in labor.
  • Additional Modifications: Aftermarket fender flares ($300–$800), adjustable track bars ($200–$400) to center the axle, and driveshaft upgrades ($300–$1,000) are often necessary to prevent vibrations.

Hidden costs include increased fuel consumption (10–20% drop in MPG), accelerated brake wear (due to added unsprung weight), and potential need for brake upgrades (larger rotors or calipers) to maintain stopping distances.

DIY vs. Professional Installation

Installing a suspension lift and re‑gearing requires specialized tools and knowledge. Lift kits are doable for an experienced DIY mechanic, but ring and pinion setup is best left to a professional due to the precision required for gear pattern and backlash. Mistakes can destroy differentials within miles. If you pay for everything, total cost for a turn-key 37-inch build easily exceeds $10,000.

Choosing the Right 37-inch Tires for Your Jeep

Not all 37-inch tires are created equal. Tread design, rubber compound, weight, and load rating all affect on-road manners and off-road capability.

All-Terrain vs. Mud-Terrain

All-Terrain (A/T): Best for daily drivers who see mostly pavement. They offer lower road noise, longer tread life (40,000–50,000 miles), and adequate off-road grip for gravel, dirt, and light rock crawling. Popular options include BFGoodrich KO2, Falken Wildpeak AT3W, and Nitto Ridge Grappler (hybrid). However, A/T tires may struggle in deep mud.

Mud-Terrain (M/T): Aggressive tread with large lugs for maximum bite in mud, rocks, and loose terrain. They are noisier, heavier, and wear faster (30,000–40,000 miles). Top picks: Toyo Open Country M/T, Cooper STT Pro, and Milestar Patagonia M/T. For hardcore rock crawling, consider sticky compound tires like BFGoodrich KM3 or Project X.

Tire Load Range and Weight

Most 37-inch tires come in Load Range D (8-ply) or Load Range E (10-ply). For a Wrangler or Gladiator, Load Range D is usually sufficient and offers a more compliant ride. Load Range E tires are extremely heavy (85–100 lbs each) and can lead to chronic wheel bearing failures, poor acceleration, and a harsh ride when not aired down. Always check the actual weight per tire—some 37s weigh as much as 40-inch tires.

Brand Recommendations

  • Nitto Trail Grappler: Excellent balance of highway manners and off-road traction; moderate weight.
  • BFGoodrich KM3: Legendary rock traction, decent road manners, but expensive.
  • Toyo Open Country R/T: Rugged-terrain hybrid that is quieter than M/T but aggressive enough for moderate trails.
  • Mickey Thompson Baja Boss M/T: Lightweight for a 37-inch M/T, with great mud performance.

Check manufacturer websites for actual mounted diameter—some 37-inch tires measure 36.2 inches, while others run over 37.5 inches. The variation can affect clearance and gearing calculations.

Performance and Handling After the Upgrade

Once the 37-inch tires are installed, expect noticeable changes in how your Jeep drives.

On‑Road Manners

Larger tires increase unsprung mass, making the suspension react slower to bumps. Highway stability may decrease if the lift geometry is not aligned properly. Expect more steering wander, especially with aggressive M/T treads. A high-quality steering stabilizer (like Fox ATS) can help. Ride quality suffers if you use Load Range E tires at high pressure—run them at 28–32 psi for daily driving to soften the ride.

Off‑Road Gains

37-inch tires provide massive ground clearance (around 3 inches more than stock), allowing you to clear larger rocks and obstacles. The larger contact patch improves traction in sand and snow. However, be extra cautious on tight trails—the wider track can lead to body damage from trees or rocks.

Braking and Steering

Stopping distance increases significantly. Consider upgrading to larger brake rotors or high-performance pads. If your Jeep has a Dana 44 front axle (common on Rubicon), the additional weight may strain the unit bearings—plan for replacement every 30,000–50,000 miles.

Running 37-inch tires may violate local laws regarding vehicle height and fender coverage. In many states, tires must not extend beyond the factory fenders. Aftermarket flares are often required to remain street legal. Furthermore, raising the vehicle more than 2–3 inches can trigger headlight aim issues—aim them down after the lift to avoid blinding oncoming traffic.

Some states require a speedometer recalibration certification, and others have specific bump steer rules. Check with your local DMV or off-road shop to remain compliant.

Safety-wise, ensure that your spare tire mount is rated for a 37-inch tire (~100 lbs). Stock carriers on many Jeeps cannot handle the weight and can fail, causing the spare to detach. Upgrade to a reinforced carrier (e.g., Teraflex or Smittybilt) or use a bumper-mounted swing-out carrier.

Maintenance and Longevity of 37-Inch Tires

Larger tires demand more frequent maintenance. Rotate tires every 5,000 miles to encourage even wear. Check air pressure monthly (cold psi) because underinflation leads to excessive sidewall flex and heat buildup that can cause blowouts. Given the added weight, monitor wheel bearings for play during every oil change—replace them proactively.

Because of the aggressive tread, 37-inch M/T tires can develop cupping if alignment is off. A quality alignment after the lift is non-negotiable.

Final Thoughts: Is the 37-Inch Upgrade Worth It?

Upgrading to 37-inch tires is transformative for off-road capability, but it is a major investment that affects cost, daily drivability, and mechanical reliability. If you are willing to spend $7,000–$12,000 beyond the tires themselves and accept the trade-offs in ride quality and maintenance, the reward is a Jeep that can conquer nearly any trail with confidence. For those who drive their Jeep primarily on pavement or only on light trails, a 35-inch tire set might be a more practical choice—requiring less lift, fewer modifications, and lower costs. Always consult with a reputable off-road builder to plan your build and ensure you get the correct components.

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