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Check spring wear pads in the hangers and equalizers. Worn pads should be replaced before the springs damage the hanger walls.  Wear will allow axle shift and cause misalignment and premature tire wear.


Check springs for broken or missing leaf sections, misalignment or wear.  Replace broken springs.  Do not weld on any spring.  Do not replace individual leaves and do not operate with broken spring leaves.


Check frame, hangers and equalizer for cracks, breaks or broken welds.  Repair or replace according to the suspension manufacturer’s specifications.  Weld all cracks before adding reinforcing plates to insure the cracks do not start again and cause failure of the repair.



Air spring suspensions, currently utilize air pressure in a rubberized, reinforced fabric bag to cushion the trailer/cargo weight transfer to the road.  The bags can be located behind, over or in front of the axle.  Some designs replace the rear spring hanger with an air bag while others have fabricated trailing arms, which pivot in a hanger and support the axle with an air bag. All air ride suspensions control the ride height with a height control air valve, which maintains the axle to frame mounting height, at any load in the trailer. Always exhaust the air in the air bags before backing the trailer to a dock for loading or unloading to reduce the tendency for “dock walk”. A trailer that has an air bag road failure can be moved slowly, for short distances, with the air totally exhausted from the air system. The axles will be supported by internal stops in the bags.

Regular periodic inspection and checks are required to insure achieving satisfactory performance.  Regular checks should be made at least every 12 months, or at once if any abnormality, poor operation or unusual wear is found.  Frequency of the checks and servicing will depend on the severity of the operation.  After a short initial break-in period of 1000 to 2000 miles, check the suspension components and verify the alignment and torque on all suspension mounting bolts and nuts per the table at the end of this section.


Check axle alignment. Also check alignment after replacing any suspension parts or if the trailer does not track behind the tractor or if unusual tire wear is noted. Move the trailer forward to a flat, level surface. Inflate the tires to the rated pressure and check the kingpin to the front axle end dimensions. The dimensions must be within plus or minus “0” to expect maximum tire mileage. Adjust using the suspension manufacturers procedures as needed. Check the front to rear axle end dimensions. These must be within plus or minus “0” to expect maximum tire mileage.


Check all bushings for wear. Replace any worn bushings and re-torque the mounting bolts and nuts to the manufacturers recommended specifications or refer to the table at the end of this section.


Check the airlines for leaks and repair or replace any parts, which cause the suspension lines to leak air.


Check the air bags for wear, leaks, deterioration, cracks, folded or misaligned sections. Replace bags that have the internal reinforcing fabric showing. Clearance around the air bags should not be less than 1-3/4” when the bags are inflated. If there is less clearance check for any deterioration or loose or misaligned parts that are the cause.


Check the hangers, trailing arms, axle seats and frame for cracks, breaks, deformed surfaces or broken welds. Repair or replace according to the manufacturers recommendations.

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