Auxiliary Axle

The CTR functions as both a tie rod and a return spring:

• As a tie rod, it delivers the industry’s first ‘passive steer’ Ackermann and does so maintenance free (no zerk fittings for lubrication). Ackermann is the technical term for optimal steering geometry and specifically highlights the amount that the inside tire turns with respect to the outside tire considering an axle’s proximity to the rear drive axle.
• The torsional wind of the bushings, in conjunction with the restoring force of the leaf spring, work together to center the steer axle, when lifted. Since these items do not fatigue over time, the result is improved performance compared to the centering and restoring action of the traditional coils over spring approach.

During installation and when the vehicle is parked straight, the leaf spring x-bar is straight and in its free state (not bent) and the bushings have zero initial windup. As the truck turns, the auxiliary axle will track with the truck turning the steering knuckles about the kingpin. At this time, the leaf spring x-bar begins to deflect into a slight S-shape and the natural rubber in the end connection winds up as the knuckle turns. The wheels then return to center due to the end connection bushings unwinding and the leaf spring x-bar straightening back to their natural positions. This logic follows for axles in the lifted position, for instance, when lifted in a turn.

The natural rubber end connection has been designed considering best practices for optimal field performance. Natural rubber is a resilient material used as a standard design approach on many Hendrickson heavy truck suspensions. It is tested to achieve >250,000 lock-to-lock turns (±31°), which is equal to over 65 fully reversed turns a day for ten years. Note that most vehicles typically achieve 10-20° wheel cut in normal maneuvers.

The CTR system does not require lubrication whereas traditional tie rods have zerk connections on the ball housing. Further, the steering dampers have been designed without the coil spring, which is a high maintenance item due to the coil spring becoming de-caged. Estimating a customer replacing (2) steering dampers and (1) tie rod per year provides an estimated annual savings of:

No. CTR with PerfecTrak Technology is a Hendrickson system with unique components that have been engineered to work together and are not backward compatible into previous generations of product.

The leaf spring x-bar is made of the same high strength spring steel used on other Hendrickson front and rear suspension products.

Yes. The leaf spring x-bar is painted before installation.
The spring is painted prior to install (vendor or Hendrickson) into the suspension and then all auxiliary axles go through our paint booth, so essentially, it is painted twice.

No. The leaf spring x-bar is parallel to the axle during installation and when the wheels are straight.

No. The steering damper is not a new design. Consider this steering damper as being the same twin tube construction as its predecessor without the coil spring. We worked with the vendor on this application and optimized the valve codes specifically for use on an auxiliary axle to dampen shimmy and optimize road feel.

Compliant Tie Rod

Customers that experience coil over damage or had systems that failed to return to center will see reduced warranty. The system comes with a 3 year warranty and will not experience the normal failure modes of other steering systems (i.e. – coil spring disengagement and tie rod deformation and end wear)

Toe setting will be simplified out of the gate and should be inspected per traditional maintenance practices. No atypical inspection required. Hardware is grade 8 (bolt) and grade c (nut) respectively with traditional coatings and should not require replacement when following typical torque procedures and maintenance practices.