Smoother Roads Ahead

| August 02, 2001

Right Time to Rebush
A walking beam suspension is designed to let the axles float out sideways as many as three inches during tight turns. Worn center bushings permit even more lateral movement, which causes tires to rub on the suspension frame hangers. Signs of scrubbing appearing on the inside sidewalls of tires mean the center bushings should be replaced to avoid severe tire damage, Hendrickson says.

Select the right bushing material for your application. For standard-duty service, rubber center bushings are recommended and require no maintenance. For more severe service, if the bushings are wearing prematurely, Hendrickson recommends high-confinement rubber bushings, bronze or fully bonded rubber bushings for extended service life.

Rubber load cushions are used instead of leaf springs on the Hendrickson RS Series suspensions. The cushions should be checked for damage and swelling at least once a year. Saddles and frame hangers can cut into the rubber and reduce the effectiveness of the cushions. Replacement cushions are available in a range of hardness ratings for different applications.

Hendrickson’s vocational suspensions use transverse rods to provide lateral support. They keep the axle centered laterally and control axle walkout while cornering. Torque rods keep the axle housing from twisting during braking and accelerating to help maintain optimum driveline angles and absorb leaning and cornering forces. The torque rods should be checked for looseness and badly worn bushings.

Air-ride suspensions use inflatable air bags or air springs – typically two per axle – to absorb road shock. The bag is a rubber/fabric bellows with a column of compressed air, which provides force and supports the load.

Air bags come in variety of sizes and shapes, including single, double and triple convoluted types and reversible sleeve models for different types of applications. Mounting brackets secure the bags to the frame rails ahead of the axles. Each bag supports a trailing arm, which is attached to the frame and allows the axle to move.

The bags are prone to damage and should be inspected regularly. Listen for the characteristic hissing sound to detect air leaking from tears, holes and abrasions, advises Firestone Industrial Products Company, whose Airide air springs are on more than half the vehicles equipped with air suspension. Misalignment can damage a bag as can overextension of the air spring. That can result in the bag pulling away from the metal top plate or from the lower mount.

The style of air spring most commonly found on heavy-duty trucks and trailers is the Firestone 1T or reversible sleeve type, a large diameter air spring that rolls up and down on a piston mounted to the bottom. Identification of the proper replacement assembly requires determining the bellows type, the bead plate and piston type used. You also need to determine if the spring includes an internal bumper, Firestone says.

The 1T style spring is available as a complete assembly, including the piston, or as a service assembly, with bellows and bead plate only. Before buying a service assembly, Firestone advises close inspection of the piston to be reused. A slight imperfection or buildup of corrosion or dirt on the piston can cause a new bellows to wear out prematurely.

Raydan Manufacturing sells Air Link, a retrofit kit to convert spring pack and rubber block suspensions from Hendrickson, Neway Anchorlock International, Ridewell Corp. and other manufacturers into an air-ride suspension. Retrofitting a Hendrickson spring pack, rubber block or solid mount walking beam suspension takes about 20 hours, Raydan says. It entails removing the original suspension, except for the walking beams, and bolting the Air Link to the frame in its place. The retrofit adds two air bags above each walking beam.

According to Raydan, Air Link offers the highest roll stability of any air-ride suspension, rivaling that of spring and rubber block suspensions, while providing a smoother ride.

Shocks Wear Out
Shock absorbers play an important role in the suspension system by dissipating axle rebounds and adding stability to the vehicle. Shocks are designed with a specific service life and should be replaced when they don’t work anymore. When a shock absorber is doing its job, the bottom section feels warmer than the upper section. When in doubt about the condition of the shock absorber, check the resistance by disconnecting it at the bottom bracket and working it with your hand. Oil leaks, excessive rust and deep dents are visible signs that shocks should be replaced.

Smoother Roads Ahead

| August 02, 2001

Right Time to Rebush
A walking beam suspension is designed to let the axles float out sideways as many as three inches during tight turns. Worn center bushings permit even more lateral movement, which causes tires to rub on the suspension frame hangers. Signs of scrubbing appearing on the inside sidewalls of tires mean the center bushings should be replaced to avoid severe tire damage, Hendrickson says.

Select the right bushing material for your application. For standard-duty service, rubber center bushings are recommended and require no maintenance. For more severe service, if the bushings are wearing prematurely, Hendrickson recommends high-confinement rubber bushings, bronze or fully bonded rubber bushings for extended service life.

Rubber load cushions are used instead of leaf springs on the Hendrickson RS Series suspensions. The cushions should be checked for damage and swelling at least once a year. Saddles and frame hangers can cut into the rubber and reduce the effectiveness of the cushions. Replacement cushions are available in a range of hardness ratings for different applications.

Hendrickson’s vocational suspensions use transverse rods to provide lateral support. They keep the axle centered laterally and control axle walkout while cornering. Torque rods keep the axle housing from twisting during braking and accelerating to help maintain optimum driveline angles and absorb leaning and cornering forces. The torque rods should be checked for looseness and badly worn bushings.

Air-ride suspensions use inflatable air bags or air springs – typically two per axle – to absorb road shock. The bag is a rubber/fabric bellows with a column of compressed air, which provides force and supports the load.

Air bags come in variety of sizes and shapes, including single, double and triple convoluted types and reversible sleeve models for different types of applications. Mounting brackets secure the bags to the frame rails ahead of the axles. Each bag supports a trailing arm, which is attached to the frame and allows the axle to move.

The bags are prone to damage and should be inspected regularly. Listen for the characteristic hissing sound to detect air leaking from tears, holes and abrasions, advises Firestone Industrial Products Company, whose Airide air springs are on more than half the vehicles equipped with air suspension. Misalignment can damage a bag as can overextension of the air spring. That can result in the bag pulling away from the metal top plate or from the lower mount.

The style of air spring most commonly found on heavy-duty trucks and trailers is the Firestone 1T or reversible sleeve type, a large diameter air spring that rolls up and down on a piston mounted to the bottom. Identification of the proper replacement assembly requires determining the bellows type, the bead plate and piston type used. You also need to determine if the spring includes an internal bumper, Firestone says.

The 1T style spring is available as a complete assembly, including the piston, or as a service assembly, with bellows and bead plate only. Before buying a service assembly, Firestone advises close inspection of the piston to be reused. A slight imperfection or buildup of corrosion or dirt on the piston can cause a new bellows to wear out prematurely.

Raydan Manufacturing sells Air Link, a retrofit kit to convert spring pack and rubber block suspensions from Hendrickson, Neway Anchorlock International, Ridewell Corp. and other manufacturers into an air-ride suspension. Retrofitting a Hendrickson spring pack, rubber block or solid mount walking beam suspension takes about 20 hours, Raydan says. It entails removing the original suspension, except for the walking beams, and bolting the Air Link to the frame in its place. The retrofit adds two air bags above each walking beam.

According to Raydan, Air Link offers the highest roll stability of any air-ride suspension, rivaling that of spring and rubber block suspensions, while providing a smoother ride.

Shocks Wear Out
Shock absorbers play an important role in the suspension system by dissipating axle rebounds and adding stability to the vehicle. Shocks are designed with a specific service life and should be replaced when they don’t work anymore. When a shock absorber is doing its job, the bottom section feels warmer than the upper section. When in doubt about the condition of the shock absorber, check the resistance by disconnecting it at the bottom bracket and working it with your hand. Oil leaks, excessive rust and deep dents are visible signs that shocks should be replaced.

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