Considering swapping to the popular off road tires 285/70r17

Things to consider when changing tires sizes, like the popular off road tires 285/70r17, on a Jeep

Upgrading to off road tires 285/70r17 on your Jeep can enhance performance, but it’s important to consider how these changes affect various aspects of your vehicle. From speedometer accuracy to gear ratio adjustments, this guide covers key considerations when changing tire sizes.

1. Understanding Tire Sizing

Tire sizes such as 285/70r17 follow a specific format:

• 285 – Width of the tire in millimeters.

• 70 – Aspect ratio (height as a percentage of the width).

• R17 – Radial construction with a 17-inch wheel diameter.

Larger tires increase ground clearance and enhance off-road capability, but they can also affect handling and acceleration.

2. Effects on Speedometer and Odometer

Larger tires affect speedometer accuracy. Since the tires cover more ground per rotation, the speedometer may show a lower speed than the actual speed.

How to Recalibrate:

• Use an OBD-II tuner to adjust speedometer settings.

• Install an aftermarket speedometer calibrator .

• Visit a dealership for professional recalibration.

According to AAA , incorrect speedometer readings can result in misreported mileage , impacting maintenance schedules and resale value.

3. Impact on Fuel Efficiency

Larger tires often reduce fuel efficiency due to increased rolling resistance and weight.

Factors Affecting MPG:

• Increased rotational mass: Heavier tires require more energy to move.

• Aerodynamics: Lifted vehicles face more wind resistance.

• Tread design: Aggressive off-road tread increases drag.

A study by the National Highway Traffic Safety Administration (NHTSA) found that switching to larger tires can decrease fuel economy by up to 10% .

4. Suspension and Lift Requirements

Jeep suspension must accommodate larger tires. The 285/70r17 tire size often requires modifications to avoid rubbing against the fender.

Recommended Modifications:

• Leveling Kit (1-2 inches) – Prevents minor rubbing.

• Lift Kit (2.5+ inches) – Necessary for off-road articulation.

• Wheel Spacers – Improve stance and clearance.

Neglecting proper clearance can lead to suspension damage and uneven tire wear .

5. Gear Ratio Considerations

Larger tires change the effective gear ratio, impacting acceleration and towing capacity.

Gear Ratio Adjustments:

• Stock Jeeps (3.21-3.73 gears) may struggle with larger tires.

• Recommended Ratio for 285/70r17: 4.10 or higher for improved torque.

• Re-gearing helps maintain performance , especially when towing.

According to Jeep Performance Research , properly adjusted gear ratios restore factory-like acceleration and efficiency .

6. Off-Road vs. On-Road Performance

Larger off-road tires improve grip on rough terrain but can impact road handling.

Trade-Offs:

Selecting tires based on driving needs prevents excessive wear and performance trade-offs.

7. Legal and Insurance Implications

Altering tire sizes may affect legal compliance and insurance policies.

Potential Issues:

• Local Lift Laws: Some states regulate maximum tire size and suspension height.

• Insurance Adjustments: Modifications must be reported to avoid claim denials.

• Warranty Considerations: Unauthorized modifications can void manufacturer warranties.

According to the Insurance Institute for Highway Safety (IIHS) , failure to disclose modifications can impact claim approval in accidents .

Final Thoughts

Upgrading to off road tires 285/70r17 enhances a Jeep’s rugged capabilities but requires thoughtful planning. By considering speedometer accuracy, fuel efficiency, suspension modifications, and legal factors, you can ensure a safe and effective upgrade for your Jeep.