Urethane is a synthetic polymer with elastic and stretchy properties, superior to rubber due to high load capacity, tear resistance, and tolerance to grease, oil, and ozone. Urethane bushings are used in heavy trucks’ suspension, steering mechanisms, and towing hitches for their durability and vibration reduction benefits.
The polyurethane polymer, or urethane, belongs to a family of chemical compounds which has characteristics similar to natural rubber; it is both elastic and stretchy. Urethane has advantages beyond those of rubber because it has a high load capacity, a better compression set, and significantly stronger tear resistance. It is also tolerant to grease, oil and ozone and has increased abrasion resistance. The compound is fully synthetic and can be molded into a very soft or hard material. Urethane bushings are frequently used in automotive parts and industrial equipment, particularly due to their advantages over rubber and their ability to be molded into unique designs.
Heavy trucks use urethane bushings in their suspension. The main types of bushings they use are a moving spoke end bushing, a moving radius center bushing and a torque arm bushing. All bushings on this type of vehicle use a polyurethane polymer. The bushing itself is made up of three layers: an outer part of the bushing, an inner part of the bushing and a polyurethane bushing part placed between the outer and inner part of the bushing, which extends the life of both the bushing part and the truck suspension. Before using urethane bushings, heavy trucks used a rubber interface, which had a shorter life span, instead of the polyurethane bushing.
Another type of urethane bushing is used on the joint that connects a tie rod to a lever arm as part of a vehicle’s steering mechanism. This joint must be constructed so that there is angular deflection and no stiffness in the mechanism. It must also be robust against excessive wear and tear if a driver uses it often. Ball joints were once used because they gave the mechanism good angular deflection, but they were expensive to build and repair. Urethane bushings are cheaper, simply constructed, have a longer life, and don’t wear as much as ball joints.
Towing hitches, like steering gears, also once used swivel joints. These types of joints attached two vehicles, allowing them to rotate at an angle relative to each other when turning left and right. The knuckle, however, wore out quickly and any shock from one vehicle was transferred to the connected vehicle, for example from the trailer to the driver’s vehicle. A different mechanism using urethane bushings reduces wear on the binding mechanism and distributes the shock effect over an extended time interval. This is also known as vibration reduction, which is a benefit for the driver.
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