Vehicle designers use tie rods to connect the steering linkage to the wheels of a vehicle. Tie rods are very durable and require little attention. Should they fail, we may lose our steering. Occasionally inspecting the condition of our tie rods can easily prevent a catastrophe.
Tie rods similar to small ball joints and allow up and down movement and rotation of the steering components. A tie rod can both turn and pivot which maintains the connection between steering and wheels as the suspension moves.
Tie rods normally come in pairs, an inner and an outer. The inner tie rod will be closer to the center of the vehicle and the outer tie rod is nearer the wheel. They normally use threads to connect the inner and outer tie rods. Turning threaded portion of the tie rods causes them to tread in and out of one another. This changes the distance between the two rod ends. This adjustment changes the angle to the tires and is the way we set the toe with a wheel alignment.
Torn tie rod boots and lubrication
Tie rods need to turn and move while loaded. Lubricant is necessary to prevent wear. Tie rods hold lubricant in and debris out with the flexible rubber boot around the tie rod base. Damage to the boot means the lubricant leaks out and contaminants get in to wear the joint. This often happens with improper service. In time the rubber may also dry rot and tear. Once the protective boot fails, the joint inevitably fails as well. Replacing most boots is not possible, so boot failure means a new tie rod.
Some tie rods have provisions to be greased but most today are sealed. While greasing may seem like a great idea, over greasing a tie rod end is as bad as not lubricating it at all. Too much grease causes the protective boot to tear. When the tie rod boot starts to expand, we have added enough grease. Continuing to add grease does not help and may rupture the protective boot. Over greasing can also be dangerous. Excessive grease from an outer tie rod end may get on the brake rotors and interfere with braking.
The fitting where we add grease is called a zerk fitting. Both the zerk fitting and the grease gun nozzle must be clean, before attempting to add lubricant. Not wiping dirt away from the fitting, before lubrication, allows debris that is on the zerk fitting to enter the joint along with the lubricant.
The lubricant used must also be correct for the application. An improper grease may not offer adequate protection and could attack the rubber in the protective boot. Always check service data for the proper lubricant, if there is any doubt.
Worn out tie rods
Eventually tie rods can wear out. As the tie rod wears it develops slack in the ball and socket. This slack allows the toe to change and the vehicle will wear the tires. Vehicles that seem to get out of alignment, often have worn tie rods. This is sometimes accompanied by a squeak noise when turning and a loose feeling in the steering.
A broken tie rod is extremely dangerous, as this is the link between the driver and the tire. When the rubber seal fails, the lubricant is lost. Debris enters the joint and rust may form. This quickly destroys the tie and a quick pull may cause it to separate. When this occurs, we lose control of the steering.
Spring loaded tie rod ends
Many tie rods are also spring loaded. A very powerful spring pushes the ball into the seat as the joint wears. This provides a joint that is shock resistant as well as wear tolerant.
Care must be used in checking tie rods for wear. Many good tie rods are needlessly replaced, sometimes with inferior aftermarket parts. The old method of squeezing the joint with a pair of pliers should never be used. This can damage the spring and quickly ruin a good tie rod. Unscrupulous operators have used this "tactic" for years to make good tie rods appear to have slack.
Properly checking tie rods
Properly checking tie rods is best done on a wheel alignment rack. The wheel is supported so that it is free to move, but still at normal height. When properly supported the tie rods are not hanging down, rather running at their normal angles. Checking tie rods that hang at an angle may give a false indication of being bad. Pushing in and out at the front of the tires will quickly show if there is slack in the tie rods. Inner tie rods are sometimes covered by a rubber cover on rack and pinion steering. In this case the cover is squeezed so that any slack can be felt.
How tie rods lock into place
Because of their extreme importance to safety, tie rods are always very securely fastened to the vehicle. Many use a taper lock to hold the joint firmly in place. This taper on the tie rod end, matches the taper in the mating component. When the parts are pulled together by tightening the nut, the tapers lock together. There is also a castle nut with a cotter pin to prevent the nut from coming loose.
Removing tie rods from their mounting is best done with tools made for the purpose. Beating on the tie rod or thread will only damage the part. Wedge shaped tools, driven between the tie rod and mount will destroy the boot and should only be used when the tie rod is going to be replaced.
Symptoms of bad tie rods include:
A squeak noise when turning or hitting bumps
A loose feeling, like slack in the steering
Shaking in the steering wheel on bumps
Tire wear to one side or the other
Properly greasing tie rods that can be greased and replacing tie rods that wear will assure years of problem free driving.