Steerable Lift-axle Suspension

steerable lift-axle suspension

The Hendrickson COMPOSILITE steerable lift-axle suspension system is engineered for enhanced durability and performance.

Although the engineering on the steerable lift-axle suspension system means that little is required other than regular lubrication, fastener and component inspection, there are events to consider. Suspension damage, component replacement or excessive tyre wear may necessitate carrying out a toe in wheel alignment. 

(Caution: Ensure that the vehicle manufacturer’s safety instructions are followed when working on the vehicle.)

Inspection

Cleaning the lift axle and tie rod prior to the inspection will improve the ability to inspect the condition of structural components. Ensure inspection is carried out on flat level surface.

Note: Do not grease the tie rod assembly before performing the inspection because the grease may mask any actual wear.

Drop lift axle and drive the vehicle one to two metres straight ahead, ensuring the axle is on a straight-ahead path. Allow vehicle to roll to a stop (do not apply service brakes) and then set parking brakes.

Turn engine off and chock the wheels on the axles other than the COMPOSILITE axle.

Raise the lift axle and support with jack stands.

On both the left- and right-hand side of the COMPOSILITE axle, measure the distance from outboard bolt head of the stabiliser to inboard bolt head of the stabiliser. If both measurements are not within 13 mm of each other it may be necessary to replace the coil-over steering stabilisers. 

steerable lift-axle suspension

Check for damage, cracking or tears in the tie rod end boots. Replace the entire tie rod end if a boot is damaged.

Check that the tie rod end nuts appear tight and secured with a split pin.

Position yourself directly below the tie rod end. Using both hands, grab the tie rod as close to the tie rod end as possible. Apply hand pressure with reasonable effort vertically up and down in a push-pull motion several times (using approximately 20 to 40kg of force). Check for any movement or looseness at both tie rod ends. 

steerable lift-axle suspension

If there is any noticeable movement in the tie rod assembly, install a magnetic based dial indicator on the Ackermann arm and measure vertical movement. Replace tie rod if there is more than 1.5mm in movement using the same force as in previous step.

Check that grease nipples are installed and in serviceable condition. Replace any damaged grease nipples with new ones.

Lubricate suspension, including tie rod ends, once inspection is complete.

Remove jack stands and lower the lift axle with the ride air springs set to the recommended operating pressure.

Adjustment

Using suitable equipment, measure suspension toe in and compare to specification.

Specification: Toe In, 1.6 to 3.2mm (1⁄16″ to 1⁄8”).

If it is not within specification, loosen the tie rod clamp fasteners on both ends and rotate the tie rod to achieve the recommended toe-in specification. Tighten the tie rod clamp bolts to 70Nm (52 ft. lb), ensuring clamp position will not foul lower shock mount at full wheel cut.

steerable lift-axle suspension

Remove alignment equipment and wheel chocks.

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steerable lift-axle suspension

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