What is a suspension tie rod?

In this brief article, we will discuss the suspension Tie rod and symptoms and causes for failure of a tie-rod.

What is a suspension tie rod?

A Tie Rod is a slender rod, usually of hollow circular cross-section, which connects the steering mechanism to the leaf and the right wheel knuckles.

In the case of an independent front suspension, the steering rack has one tie-rod at each end, left and right, that connect to the left and right wheel knuckles respectively. In the case of a rigid axle front suspension, the Tie-rod is a single bar that connects the left and right wheels.

The connection between the Tie-Rod and the knuckle is through means of a Ball-joint. Tie-rods are of two-piece threaded design, generally adjustable in length. The two pieces of the toe-rod are joined by a male-female thread along with a lock-nut to prevent it from loosening after adjustment.

How does a Tie Rod work?

There are two types of steering systems, namely, 

  • Rack-and-pinion steering system, and
  • Recirculating ball or mechanical steering. 

A rack-and-pinion steering system operates in a very simple linear way. When the steering wheel is turned, a pinion gear, attached to the steering shaft, rolls along the length of the steering rack. The steering rack moves either left or right, according to how the wheel is turned. The tie rods are attached through ball-joints to the steering rack on one side and to the steering arm at the other. The Tie Rod is responsible for transmitting the force back and forth between the steering rack and moving the wheel.

What are the uses of a tie rod?

  • The Tie Rod’s primary purpose is to transfer Steering forces back and forth between the steering system and the road wheels.
  • The Tie-rod is almost always of Adjustable length and therefore used for adjusting the Static toe-setting in the front wheels.

Is the Tie rod part of suspension?

Yes, the Tie Rod is part of the Suspension as well as the steering system. By definition, a suspension arm transmits forces from the road to the chassis. The Tie rod does fulfill this function by giving feedback of the tire forces back to the steering rack and the steering wheel. On the other hand, the Steering forces from the steering rack are transmitted to the wheels through the tie rod. 

What are the types of Tie Rod ends?

There are basically 2 types of Tie Rod end Ball joints, namely, the Serviceable and Non-Serviceable type. The Non- serviceable type of ball-joint comes with a Rubber boot that seals the ball-joint grease and protects it from leaking out of the joint.

The serviceable Type of ball-joint is a sort of older, but more durable type of ball-joint. Here, the ball-joint is provided with a grease-nipple, through which the joint can be greased at the stipulated intervals.

The serviceable ball-joints, if greased regularly, will last longer than the non-serviceable ball-joints. The reason being that the non-serviceable ball-joint outer rubber boot is subject to weathering and cracking over time. Once the rubber boot cracks, it no longer protects the ball-joint and allows grease to escape. After the Rubber boot fails, the ball-joint is not repairable and has to be replaced.

What are the symptoms of a bad tie rod?

The symptoms of a bad Tie Rod are:

  • Continuous Knocking noises while driving over =normal roads as well as rough roads
  • Uneven Tire Wear issues
  • Steering wheel Vibration at high speed
  • Poor handling at high speeds, the steering feels vague and handling response is poor

In order to verify if the tie rod is bad, get the car body lifted with the wheel hanging. Hold the tire with both hands in a 3 o’clock – 9 o’clock position and try to steer the wheel side to side with your arms. If you hear a knocking sound, then it is almost sure that the tie-rod ball joints are worn out.

What are the causes for Tie-Rod failure

The tie rod comes with 2 ball joints; one at each end. These ball-joints can either be of the serviceable or unserviceable type. The ball joint is basically a sliding joint, wherein a socket slides over a ball, to provide a swivel movement. This type of joint functions only when it is sufficiently lubricated. Many times, the ball-joint is serviceable, or the joint is enclosed, but has an inlet to pump grease into the joint and provide lubrication to the sliding surfaces. 

In other cases, the ball-joint is a ‘sealed-type’ meaning that the lubrication has been filled at the factory and cannot be replenished. Such types of joints are protected by an outed rubber boot that acts as the seal that prevents the lubrication from escaping. Once the rubber boot fails, it lets the lubrication escape, thus leading to the ultimate failure of the joint.

How much does it cost to replace a tie rod?

The Tie-rod is not a very expensive part. The part can be replaced at the cost of $50 to $150, depending on the make of your car. The replacement procedure is quite easy and does not require you to jack the vehicle. The replacement can very well be done on a parked vehicle.

Conclusion

In this brief article, we have discussed the suspension Tie rod and symptoms and causes for failure of a tie-rod.

In case of any queries or comments, please feel free to ask.

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