Tie rods transfer and control motion between components in machines and motor vehicles. Each front wheel on most automobiles has its own tie rod to connect it to the power steering unit. Six or more tie rods may also control the motion of each of the four wheels in sophisticated automotive suspension systems to deliver high-performance handling along with a smooth ride. Tie rods usually have pivoting or ball joint ends that allow the parts they connect to swivel, rock, or turn in whatever positional orientation is necessary to accomplish their function.
These bars are also used as connecting rods to resolve linear motion into rotating motion with crankshafts and crank wheels on machines and appliances. They allow one motor or transmission output to actuate a number of functional levers, arms, or shafts connected to it. A tie rod usually has a threaded length adjustment section that allows the rod to be tailored to the exact needs of a mechanical application. Since they can transmit large forces, they are usually made of high-strength tempered steel and plated to protect against corrosion.
Tie rods are extensively used for steering control on many modes of transportation besides cars and trucks. On boats and ships, they move outboard motors, stern drives, and rudders. Airplanes of all types use tie rods to connect mechanical and hydraulic actuators to flight control surfaces on wings and stabilizers. They also help raise and lower landing gear, open and close doors and hatches, and control the motion of seats and seat backs.
Riding lawn mowers, snow throwers, and many other powered implements, including farm tractors and harvesters, use the tie rod mechanism extensively to control the motion of their functioning parts. This can include height adjustments and horizontal and vertical orientation. In the living room, the tie rod allows the recliner to tilt to that just-right position for a nap. It would be practically impossible to create those exciting amusement park rides without tie rods securely connecting major components.
Tie rods play a key role in automotive performance and safety, and should be carefully inspected during periodic maintenance. While they are designed to perform reliably for many years, driving too hard over obstacles such as curbs and potholes can bend a tie rod, or pound its ends loose. While some car makers use maintenance-free tie rods, some do recommend lubrication each time the oil is changed.