The ‘shocking’ evolution of a smooth ride

Parts Jason Cannon February 27, 2013

While their function has barely changed in generations, the technology that goes into manufacturing shocks has evolved significantly.

Essentially, a shock absorber is only four pieces: a piston, a cylinder, a piston rod and a lubricant.

But while its engineering may seem simple, advancements have brought the components a long way.
Most manufacturers use split shock eye rings, but in the mid-90s, Gabriel launched a deviation from the standard: a solid steel eye ring.

“That provides reinforcement when the ring is welded to the rod,” says Gabriel Marketing and Communications Manager Christine Fisher. “With a split eye ring, any misalignment of the two sides of the split to the top of the rod will result in a weaker or reduced weld.”

Marketplace demands drive many component improvements. For instance,

Tim Bauer, director of Undercarriage Products at Meritor, says consumer feedback prompted his company to enter the shock absorber market this year with innovations of its own.

“It all came down to some of the fleet issues, and we wanted to solve those issues,” he says.

Among the most oft-referenced fleet concerns were excessive shock misting and leaking.

Misting is a normal and necessary function of a shock absorber, but excessive misting can lead to a rough ride, premature wear or be an indicator of other problems.

Misting occurs when the hot piston rod is drawn out of the shock body and the microscopic film of hot oil on the rod turns to vapor. This vapor, or mist, condenses when it reaches the cooler outside air and forms a film on the outside of the shock body.

Throughout this mechanical process, by design, the shock’s piston rod carries a film of oil through the rod seal to lubricate the seal lips. With one small alteration in this step, Bauer says, Meritor virtually eliminated excessive misting and leaking concerns.

“In our premium adjustable (shock), the hydraulic fluid has different viscosity,” he says. “As the fluid heats up, it doesn’t pass the seal lip.”

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