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7 Reasons a Zero Turn Mower Won’t Drive Straight (SOLVED)

Your zero-turn is no longer driving straight and has begun to pull to one side. Sometimes you can compensate for this by slightly adjusting the steering levers to make it drive in a straight line, but this isn’t the ideal situation.

It’s best to find and fix the cause of the problem not only to get the mower to no longer pull to the left or right, but just in case the cause can result in a more significant issue if it isn’t repaired.

A zero-turn may not drive straight and have a steering problem due to the tire pressure being wrong, the dampers failing, or air in the hydraulic system.

The zero-turn may only need a tracking adjustment or an attachment is throwing the mower off-balance.

Zero turn won't drive straight

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

Zero Turn Pulls to One Side or Won’t Drive Straight

1. Incorrect Tire Pressures or Wrong Size Tires

The first thing to check when your zero-turn begins to pull to one side is the tire pressure. A low tire will cause the mower to not drive straight.

In addition to making sure the tire pressures are correct and equal on each side of the mower, confirm the tires are the same size. Using two different-sized tires can also contribute to a mower continuing to pull to one side.

SOLUTION: Confirm the tire sizes are the same for the left and right drive tires. Then check the tire pressures and ensure the tires are filled to the manufacturer’s specifications.

The tire pressures must be equal on each side of the zero-turn.

2. Tracking Adjustment

The zero-turn may require a tracking adjustment if the mower no longer moves forward in a straight line and veers to the left or right.

You will find linkages from the steering levers to a plate on the hydraulic motors. Adjustments vary by manufacturer and model. Consult your operator’s manual for tracing instructions.

SOLUTION: Adjust the speed adjustment bolt to change the rotation speed of the tire so each tire moves at the same speed. Refer to your operator’s manual.

3. Brake is Hung Up

Check the brakes on your zero-turn. The brake can fail on one side causing the tire to drag and not move.

SOLUTION: Follow these steps to identify a wheel that won’t spin freely because the brake is hung up.

  • Place the mower on a flat surface and set the parking brake.
  • Chock the front wheels so the mower doesn’t roll forward.
  • Raise the rear drive tires off of the ground using jack stands.
  • Disengage the hydros by releasing the transmission bypass levers.
  • Release the parking brake.
  • Spin each drive wheel to check for resistance.
  • If you find resistance in one of the wheels, remove the wheel and inspect the braking system. This will vary by zero-turn. Consult a parts diagram to identify the brake parts on your zero-turn. Make necessary repairs.

4. Air in the Hydraulic System

Air in the hydraulic system will not only cause the mower to move slower, but it can also cause it to pull to one side.

Your zero-turn has two independent hydraulic pumps and wheel motors: one for each side of the mower. If air is trapped in the hydraulic system on one side of the mower, it can cause the wheel on that side to move slower.

SOLUTION: Remove air from a zero-turn hydraulic system:

Air can be removed from the system on most zero-turn mowers by placing the mower on a flat surface.

  • Secure the front wheels using wheel chocks to prevent the mower from rolling forward.
  • Raise the rear drive tires off of the ground using jack stands.
  • Release the bypass levers so they are in the OPEN position.
  • Start the engine and remove the parking brake.
  • Using the speed levers, move the levers forward and backward about 6 times.
  • Stop the engine and engage the parking brake.
  • Close the bypass levers so they are in the CLOSED position.
  • Using the speed levers, move the levers forward and backward about 6 times.

Repeat these steps as necessary until you don’t hear excessive noise and the wheels move at normal speeds. When air is removed from the system, the oil level goes down. Check the hydraulic oil level and add more oil as needed so it is at the full level.

Refer to your operator’s manual for detailed steps to remove air from your model’s hydraulic system.

5. Bad Dampers

If you are experiencing a jerky movement when operating your zero-turn, the steering dampers may be loose or bad.

The steering dampers, often referred to as shocks, are used to absorb negative feedback from the hydro pumps that cause the jerky movement that can cause the mower to pull to one side.

You will find a steering damper on each side of the mower.

The dampers (sometimes referred to as steering shocks) will wear over time. You will find a damper on each side of the mower attached to the bottom of the steering arm.

Like other parts, the damper can become worn and no longer function correctly.

SOLUTION: Replace a bad steering damper(s).

6. Weak Transmission

If you have checked the items above and find you the mower is still pulling to one side, it may be due to a weak transmission.

Your zero-turn runs two independent transmissions. So, if one side becomes weak and begins to fail, the mower will pull to the side and no longer drive straight.

SOLUTION: Consult your lawn mower dealership for repair. Your dealer can diagnose a pump and wheel motor failure and replace it if needed.

7. Attachment Making Zero Turn Off-Balance

Some people choose to tow a small trailer or other items behind their zero-turns. If you are one of them, if the load you are pulling is not balanced at the rear of the mower, it can cause the mower to pull to one side.

SOLUTION: Balance the load.

Take caution when pulling items with your zero-turn. Do not exceed your zero-turn’s towing capacity. The transmissions are not designed for pulling heavy loads. This can damage them and result in a costly repair.