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6/99 - Tech Tips

Suspension Maintenance: When It Comes To Re-Bushing, It's As Easy As One, Two...And That's It

WOODRIDGE, IL - Time to re-bush your suspension? If so, William Adlaf, manager of technical services at Hendrickson Truck Suspension Systems, offers some helpful advice. According to Adlaf, there's a significant amount of misconception in today's trucking industry regarding how and when to re-bush the center bushings of a heavy-duty suspension. Luckily he adds, adhering to two relatively simple yet highly important keys, will go a long way in maximizing the effectiveness of this essential maintenance program. The keys are: knowing when to re-bush, and, selecting the right bushing material.

Knowing when

Signs of excessive axle walkout are a sure signal of impending trouble. If axles fail to re-align themselves after maneuvering through a curve, for instance, it's a good bet that re-bushing is necessary. That's because beam center bushings control the lateral movement of the axles during cornering. Also during cornering, a good center bushing should allow for up to three inches - and no more - of lateral movement under load.

Worn center bushings can result in increased lateral movement of the axles on turns, often well beyond the allowable three inches. This will then cause the inside walls of the tires to rub on the suspension frame hangers. To avoid serious tire damage, the center bushings should be replaced.

Once the need for center bushing replacement has been established, the next - and even more important - decision should focus on selecting the proper bushing material. And that decision is, more often than not, based on the severity of application and vehicle weight. Hendrickson offers four center bushing options. All have been designed for specific applications and getting the best possible suspension performance.

Center bushing selection - rubber vs. high confinement, rubber vs. fully bonded vs. bronze

Most rubber center bushings perform well when placed in standard duty applications. Accordingly, Hendrickson recommends the use of rubber bushings as a highly economical component that requires no maintenance while providing long life in a variety of vocations.

However, when rubber bushings appear to be wearing prematurely, Hendrickson's high confinement rubber bushings are available. These products serve as a fine intermediary between rubber and bronze, with no sacrifice to ride quality - a drawback often associated with urethane bushings. High confinement bushing also are an inviting option for many maintenance professionals, simply for the extended service life they provide.

For extra heavy loads or highly severe applications, Hendrickson has two options - fully bonded rubber bushings or bronze bushings. While the fully bonded bushing requires the use of transverse rods, it still requires no maintenance and typically results in long service life under the most severe of trucking applications. Bronze should be the choice when vehicles are expected to encounter a large amount of tight cornering conditions. As an added benefit, these products are more resistant to axle walkout. Note that preventative maintenance is required with bronze bushings, but extended service life can be the fortuitous result.

Regardless of application, summarizes Adlaf, timely service and the use of genuine parts when re-bushing a suspension system, will go a long way in maintaining the useful life of this important heavy truck component.

Hendrickson, with 21 facilities worldwide, is one of the largest international suppliers of truck, tractor and trailer suspensions, lift axles, springs, bumpers, and stamped components to the commercial transportation industry. Having manufactured more than two million truck suspensions, Hendrickson has been meeting suspension needs for more than 70 years. Hendrickson Truck Suspension Systems, a certified QS-9000 supplier, is headquartered at 800 South Frontage Road, Woodridge, IL 60517-4904.