Bearing up - WIP - Brief Article

Automotive Design & Production, Sept, 2002 by Kermit Whitfield

The integration of electronics into the chassis of vehicles has imbued even what were once considered simple components with intelligence. Case in point: wheel bearings. These long ago evolved from the heavily-greased variety dear to the shade tree mechanic to sealed assemblies. Now the bearings are part of wheel end modules that incorporate internal sensors capable of measuring loads and performance and feeding that information back to the central processing units of anti-lock braking systems. The Timken Company [Canton, OH] pioneered the modules back in the early 1990s with the introduction of its Sensor-Pac, and now holds the lion's share of the market it essentially created for pick-ups and SUVs. A key to the success of the Sensor-Pac, and the many variations that have sprung from it, is that Timken was able to place sensors within the sealed bearing assembly itself, replacing externally mounted ones that were subject to dirt and debris. The resulting reduction in both assembly and warranty costs got the automakers' attention and business.

Timken's latest wheel end module is the "Generation III." The main advance of this design is the integration of the bearing raceway with the hub, which reduces unsprung weight and narrows the overall package width. The smaller package allows designers to enhance durability by beefing up hubs, seals and mating components. It also leads to a reduction in the scrub radius (the distance from the point where the steering axis meets the ground, to the center of the contact patch of the tire) which improves braking and maneuverability. The Generation III is currently on the Dodge Ram 1500 series and is slated to go on an upcoming full-size truck and SUV program.

But even with advanced products like the Generation III, Timken officials say getting makers to switch from cheaper ball bearing-based designs to their tapered roller bearings is often an uphill battle. However, as vehicle weight and performance increases, Timken's products become an easier sell. One recent example: when Chrysler added a performance version of its PT Cruiser, it found that its ball-bearings couldn't handle the added strain, so it turned to Timken with a quick development request. A short nine months later the new bearings were ready. And Chrysler liked them so much that it made them standard equipment on all PT Cruisers.