Why Install BFG KO2s on a 4-Inch Lifted Jeep

A 4-inch suspension lift is a transformative modification for Jeep Wrangler (TJ, JK, JL) and Gladiator (JT) owners. It provides the necessary ground clearance and suspension travel to tackle serious off-road terrain while maintaining a functional, road-legal package. The true potential of this lift, however, is unlocked when you pair it with the right set of tires. The BFGoodrich All-Terrain T/A KO2 has been the gold standard for light truck tires that need to perform in mud, snow, and rock without sacrificing highway stability. Installing BFG KO2 Mud Terrain tires on a 4-inch lifted Jeep is a strategic upgrade that enhances traction, sidewall durability, and overall off-road confidence.

This guide provides a production-ready, step-by-step installation process. Whether you are mounting the tires on a brand-new set of wheels or your existing factory rims, following these procedures will ensure a safe and precise installation that maximizes the lifespan and performance of your new tires. We cover everything from selecting the optimal size and load rating to the critical post-installation torque checks.

Selecting the Correct BFG KO2 Size and Load Range

Before you lift a finger on the installation, you must verify that your chosen tire size and load rating are appropriate for your specific 4-inch lift kit and Jeep model. A 4-inch lift typically provides enough clearance for tires ranging from 33 inches to 35 inches in diameter.

Common Fitments for a 4-Inch Lift

  • 33 x 12.50 R17: A highly popular size for JK and JL models. It offers excellent off-road grip with minimal modifications. You will likely not need to adjust bump stops or trim fenders.
  • 35 x 12.50 R17: This is the "sweet spot" for a 4-inch lift on most Wranglers. It provides a massive visual upgrade and serious tire contact patch. However, it often requires aftermarket bump stops, extended brake lines, and offset control arms to prevent rubbing at full flex or full steering lock.
  • 35 x 12.50 R15: Common for older TJ and YJ models running 15-inch wheels. Ensure your wheel backspacing is adequate (typically 3.5 to 4.5 inches).

Understanding Load Range (C vs. D vs. E)

The BFG KO2 comes in various load ranges, which dictate the tire's maximum pressure and weight capacity. For a lightweight Jeep used primarily for overlanding and daily driving, a Load Range C or Load Range D tire is ideal. It provides a compliant ride and enough sidewall flex for airing down on the trail. A Load Range E tire, while extremely durable, has a very stiff sidewall that can negatively impact ride quality on a lighter vehicle like a Wrangler. Always check the tire's sidewall for the recommended cold tire pressure (usually 35-37 PSI for Jeeps).

For a comprehensive fitment guide, consult resources like ExtremeTerrain's lift and tire calculator to cross-reference your specific lift kit and wheel offset.

Tools and Materials Checklist

Gathering the correct tools before you start will prevent unnecessary trips to the hardware store and ensure a safe workflow. You will need:

  • BFG KO2 Tires (matched set of 4 or 5).
  • Floor Jack with a minimum 3-ton (6,000 lb) capacity.
  • Jack Stands (x2) with a matching 3-ton rating. Never rely on a jack alone.
  • Wheel Chocks for the rear wheels.
  • Breaker Bar (1/2-inch drive) and a Torque Wrench (1/2-inch drive, capable of 100-150 ft-lbs).
  • Correct Socket Size (Common sizes for Jeeps: 13/16", 7/8", or 21mm for modern JL/JT models).
  • Anti-Seize Compound (critical for preventing steel lug nuts from fusing to aluminum studs).
  • Wire Brush for cleaning hub mounting surfaces.
  • Tire Pressure Gauge and Air Compressor (or visit a local gas station).
  • Torque Extensions (if needed for aftermarket deep-dish wheels).
  • Optional: Impact gun (for quick removal), TPMS rebuild kit (if swapping to new wheels).

Step 1: Prep and Safety

Safety is the primary concern when working with heavy tires and jacks. Park the Jeep on a flat, level, concrete surface. Engage the parking brake fully. Place wheel chocks securely behind the rear tires (if lifting the front) or in front of the front tires (if lifting the rear).

Using a breaker bar, break the lug nuts loose on the wheel you are removing while the Jeep is still on the ground. Do not remove them completely—just crack them free. This prevents the wheel from spinning while you try to loosen the nuts later.

Step 2: Removing the Old Tires

  1. Lift the Vehicle: Position the floor jack under the designated axle lift point (usually the differential housing or a reinforced frame rail). Jack the vehicle up until the tire has enough clearance to slide out, then place a jack stand under the axle's spring perch or specified lift point. Lower the jack slightly until the vehicle rests securely on the stand. Repeat for the opposite side if doing both front or both rear.
  2. Remove Hardware: Remove the loosened lug nuts completely. Place them in a container (a magnetic tray is ideal) to avoid losing them. Grip the tire at the 9 o'clock and 3 o'clock positions and pull it straight off the hub. If it is stuck, carefully tap the back of the tire with a rubber mallet or use a penetrating oil like WD-40 around the hub centric ring.
  3. Inspect the Hub: Use a wire brush to thoroughly clean any rust, dirt, or old anti-seize from the wheel hub and the back of the brake rotor. A clean mounting surface is essential for preventing vibration.

Step 3: Preparing the BFG KO2 Tires for Installation

If you are having the tires mounted and balanced at a shop (highly recommended for proper bead seating and balancing with a road-force balancer), you can proceed directly to mounting the wheel/tire assembly. If you are mounting the tires onto the wheels yourself, pay attention to these details:

  • TPMS Sensors: Ensure your tire pressure monitoring system sensors are properly installed and programmed to steer the vehicle. For Jeeps, this usually involves programming the sensor IDs using a TPMS tool or an aftermarket programmer (like a Tazer or Flashcal).
  • Bead Seating: After inflating, seat the beads fully. You will usually hear two loud pops. Inflate to the recommended maximum pressure listed on the sidewall to ensure a solid seat, then immediately deflate to your desired cold tire pressure (typically 35-37 PSI for daily driving).
  • Directional Tread: The BFG KO2 has a specific tread pattern designed for forward rotation. Ensure the arrows on the sidewall point in the correct direction of rotation for each corner of the vehicle. Sometimes tires are mounted backwards by mistake, leading to poor mud shedding and road noise.

Step 4: Installing the New Tires and Wheels

  1. Apply Anti-Seize: Apply a thin layer of anti-seize compound to the wheel studs. This is critical for Jeeps, especially those driven in salt or snow, to prevent the lug nuts from seizing to the studs. Do not get anti-seize on the rotor surface.
  2. Mount the Wheel: Align the wheel with the hub. Hang the tire on the studs gently to avoid cross-threading. If the wheel has a tight fit, use a rubber mallet to gently tap it into place around the hub centric ring.
  3. Hand-Tighten: Thread the lug nuts on by hand until they are snug. Do not use an impact gun for final tightening as it can easily over-torque the studs or cross-thread them. Make sure all nuts are seated flush against the wheel.
  4. Tightening Sequence: Lower the vehicle from the jack stands so the tire is on the ground but not bearing full weight. Use a torque wrench to tighten the lug nuts in a star pattern.
  5. Torque Specifications:
    • Jeep Wrangler TJ (1997-2006): 90-100 ft-lbs.
    • Jeep Wrangler JK (2007-2018): 95-125 ft-lbs (check your specific model year sticker on the glove box).
    • Jeep Wrangler JL & Gladiator JT (2018+): 130 ft-lbs.
    Tighten in stages (e.g., first pass at 50 ft-lbs, final pass at the spec value).

For a comprehensive torque spec chart for your specific vehicle, always consult a reliable source like Jeep's official site or a trusted aftermarket parts retailer.

Step 5: Post-Installation Inspection

Once all four tires are installed, perform a series of critical checks before and after your initial test drive.

Clearance Check

With the vehicle on the ground, turn the steering wheel to full lock in both directions. Listen and feel for any rubbing against the fender liners, sway bar, or control arms. If you hear rubbing, you may need to adjust bump stops or trim the fender liners. A 35-inch tire on a 4-inch lift often requires an off-set control arm alignment to clear the lower control arm mounts.

Air Down Procedure

If you are heading directly off-road, lower the tire pressure to around 15-18 PSI for rock crawling or 20-25 PSI for overlanding terrain. Always carry a portable air compressor to reinflate before hitting the highway.

Speedometer Recalibration

Larger tires require a speedometer recalibration. Without it, your speedometer will read too fast, and your transmission shift points will be off (important for JL/JT automatics). Use an aftermarket tuner (Superchips, Diablosport, Tazer) or dealer-level software to adjust the tire size in the PCM. Learn more about recalibrating your Jeep's computer in this guide to speedometer recalibration.

Step 6: The 25-Mile Torque Re-check

This is the most overlooked step in tire installation. After driving for approximately 25 miles (a mix of street and highway driving), the thermal cycles and settling of the wheel against the hub can cause the lug nuts to loosen. Retorque every lug nut to the manufacturer's specification in the proper star pattern. Repeat this check again after 100 miles. Failure to perform this re-check can lead to catastrophic wheel separation.

Caring for Your BFG KO2s

To maximize the lifespan of your tires, adhere to a strict maintenance schedule. Rotate your tires every 5,000 to 7,000 miles. For a Wrangler, a 5-tire rotation is highly recommended to ensure the spare wears evenly and can be used in an emergency. Always check tire pressure when the tires are cold (after sitting overnight) for the most accurate reading.

Avoid sidewall punctures by inspecting the "Sidewall Armor" layer. While the KO2 is incredibly tough, rocks can still chip the lugs. If you notice excessive chipping, it often indicates that the tire pressure is too high for the terrain you are running.

Conclusion

Installing a set of BFG KO2 Mud Terrain tires on your 4-inch lifted Jeep is one of the most impactful modifications you can make. It immediately improves your off-road capability, handling, and aesthetic appeal. By following these precise steps—from selecting the correct load range to the critical 25-mile retorque—you ensure a safe, professional-grade installation that will perform flawlessly for thousands of miles. Whether you are crawling over rocks in Moab or navigating a snowy mountain pass, the combination of a proper lift and a proven all-terrain tire is the foundation of a highly capable adventure vehicle.