Bendix Spicer Foundation Brake’s continued fleet testing of its Bendix Versajust LS Slack Adjuster with the WearMax Clutch has shown that the automatic slack adjuster can extend lining life by up to 16% and brake drum life by up to 30%, while improving safety and compliance. Launched in 2011, the Versajust introduced key enhancements to automatic slack adjuster technology with its WearMax clutch, which allows for a gradual, continuous, and more precise adjustment of the running clearance between the brake shoe and drum.
“Versajust’s unique adjustment rate enables a tighter running clearance, which provides the maximum brake chamber reserve stroke and creates a quicker response time for brake application. This makes it a valuable component, especially in today’s environment of Compliance, Safety, Accountability (CSA) scoring and the Reduced Stopping Distance (RSD) mandate,” explains Gary Ganaway, Director of Marketing and Global Customer Solutions at Bendix Spicer Foundation Brake LLC (BSFB).
“In addition to bolstering the safety proposition for fleets, Versajust can save fleets money by extending lining and drum life, while lowering the maintenance costs associated with brake adjustments,” Ganaway says. “In contrast to Versajust, most slack adjusters on the market – while attempting to achieve this tight clearance – adjust prematurely as the drum heats and expands during normal braking. When the drum cools down again, that running clearance is reduced – or even eliminated – which can result in a dragging brake, higher brake temperatures, and accelerated wear.”
According to Ganaway, dragging brakes mean reduced fuel economy and maintenance costs can increase by creating the need for frequent brake adjustments. He states that fleets may not be aware that they have an issue with dragging brakes, and may believe they are experiencing typical lining and drum life. However, if they regularly need to back off the slack adjuster during maintenance, or are unable to rotate a tire or remove a drum, it may be a strong indicator of over-adjustment by the slack adjuster.
Although some slack adjuster manufacturers create a larger running clearance to help avoid the problem of dragging brakes, doing so increases the necessary “free stroke” – the amount of adjuster arm movement that’s needed to move the brake shoes against the drum. This increases brake timing and reduces the brake’s effective chamber stroke, reducing the vehicle’s margin of safety and increasing the risk of roadside inspection violations. In contrast, the Versajust’s longest free stroke is just five-eighths of an inch, which maximizes both brake reserve and the compliance margin.
“Because brake stroke has a direct impact on braking performance and highway safety, it is a focal point during roadside inspections,” Ganaway says. “In 2013, during the Commercial Vehicle Safety Alliance-sponsored Roadcheck inspections in June and its Brake Safety Week inspections in September, more than 5,500 vehicles – or nearly 1 in 10 trucks in the United States and Canada – were removed from service due to brakes being out of adjustment.”
In addition to the WearMax Clutch, the Versajust slack adjuster features patented bronze friction rings, increased corrosion resistance, and a stronger seal to provide durability across a range of environments and duty cycles. It is also engineered for easy installation and maintenance without the need for special tools, attachments, templates or brackets.
