Why Does an SUV Power Liftgate Fail After Installing a Rear Spare Tire Carrier?

Rear spare tire carriers are common upgrades for off-road SUVs, overland vehicles and expedition builds. They improve exterior storage and help prepare the vehicle for long-distance travel.

However, once a spare tire carrier is installed on the tailgate, the factory power liftgate system may no longer work correctly.

The Short Answer

Installing a rear spare tire carrier can increase the overall tailgate weight by approximately 30–60 kg, depending on the vehicle model, carrier structure, tire size and mounting position.

The factory power liftgate system is designed and calibrated according to the original tailgate weight, original center of gravity, factory hinge geometry and standard motor load.

After the spare tire carrier is added, the tailgate load distribution changes significantly. The center of gravity may move farther away from the hinge axis, increasing the torque required to open, hold and close the tailgate.

As a result, the electric tailgate struts, lift motor, hinges, brackets and control system may be forced to operate beyond the original OEM design range.

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Why Does a Spare Tire Carrier Create More Stress?

Power liftgate performance is controlled by torque, not weight alone.

A simplified engineering relationship is:

Required hinge torque = load force × horizontal distance from center of gravity to hinge axis

This means two SUVs with the same added weight may still require different liftgate force if the spare tire carrier position, tailgate size or hinge geometry is different.

When the spare tire is mounted farther from the hinge axis, the torque load increases. This makes the liftgate system work harder during opening, holding and closing.

Common Power Liftgate Failures After a Rear Spare Tire Carrier Upgrade

When the factory system is overloaded, these problems may appear:

• The power liftgate cannot open completely

• The tailgate drops automatically after reaching the fully open position

• The electric tailgate struts become bent or deformed

• The power liftgate cannot perform repeated opening and closing cycles

• The drive motor becomes overloaded

• The system makes abnormal noise during operation

• The tailgate reverses unexpectedly during closing

• Hinges or mounting brackets experience excessive stress

• The power liftgate motor fails prematurely

These issues are usually caused by a mismatch between the modified tailgate load and the original power liftgate design.

Why Replacing Only the Electric Tailgate Struts Is Not Enough

Many workshops first try to solve the problem by replacing the original struts with stronger electric tailgate struts.

This may improve lifting force temporarily, but it does not always solve the root cause.

A power liftgate is a complete system. If only the struts are upgraded, other components may still remain overloaded, including:

• Drive motor

• Gear transmission

• Tailgate hinges

• Mounting brackets

• ECU control parameters

• Anti-pinch calibration

• Latch engagement

• Vehicle body mounting points

In some cases, stronger struts without proper system calibration can create new risks, such as difficult manual closing, inaccurate obstacle detection, excessive bracket stress or unstable tailgate movement.

What Should a Heavy-Duty Power Liftgate Solution Include?

A reliable heavy-duty electric tailgate system for SUVs with rear spare tire carriers should be designed as a complete engineering upgrade.

Key components may include:

1. Heavy-Duty Electric Tailgate Struts

The struts must provide enough support for the modified tailgate while maintaining smooth and controlled movement.

For some heavy-duty SUV applications, the closing force requirement may reach:

F2 ≥ 1500 N

This value should be treated as a project-specific reference, not a universal standard for all vehicles. The final force must be selected according to the actual tailgate weight, center of gravity and installation geometry.

2. High-Torque Drive Motor

The motor must provide enough torque to support repeated opening and closing cycles without overheating or premature failure.

For certain heavy-duty power liftgate configurations, the motor stall torque may reach:

Stall Torque ≥ 12 N·m

However, stall torque alone is not enough to evaluate the system. Engineers should also review rated operating torque, current consumption, thermal protection and cycle durability.

3. Vehicle-Specific ECU Parameter Calibration

After the tailgate load changes, the control system must be recalibrated.

Important calibration areas include:

• Opening speed

• Closing speed

• Anti-pinch force threshold

• Motor current limit

• Soft-start and soft-stop behavior

• Height memory function

• Auto-reverse logic

• Manual emergency operation

Without correct ECU calibration, even a stronger mechanical system may still operate unreliably.

4. Structural and Vehicle-Level Validation

Before production approval, the complete system should be tested on the modified vehicle.

Recommended validation items include:

• Repeated opening and closing cycle tests

• Hold-position stability test

• Slope operation test

• Anti-pinch safety test

• Motor current and temperature monitoring

• Hinge and bracket stress inspection

• Noise and vibration evaluation

• Latch closing reliability test

• Manual operation test

Engineering Data Required Before Customization

Before selecting a heavy-duty power liftgate system, engineers should confirm:

• Vehicle model and production year

• Original tailgate weight

• Final tailgate weight after modification

• Spare tire carrier weight

• Spare tire size and weight

• Mounting position of the carrier

• Tailgate center of gravity

• Hinge geometry

• Original strut dimensions

• Required opening angle

• Required opening and closing speed

• Electrical system capacity

• Environmental and durability requirements

This data allows the system to be designed based on real vehicle conditions instead of guesswork.

Conclusion

Installing a rear spare tire carrier changes more than the appearance of an SUV. It changes the mechanical load, center of gravity and torque demand of the entire tailgate system.

For off-road SUVs, overland vehicles and professional modified vehicles, factory power liftgate systems may not be suitable after the tailgate weight increases by 30–60 kg.

A reliable solution requires a complete heavy-duty power liftgate system, including heavy-duty electric tailgate struts, high-torque drive motor, reinforced structure and vehicle-specific ECU calibration.

TOMASTER is a professional manufacturer of custom power liftgate systems, providing heavy-duty electric tailgate solutions for SUVs equipped with rear spare tire carriers, armored vehicle conversions and off-road vehicle modifications.