Though you may never even see it, a wheel hub bearing unit is an important part of a car’s wheel assembly, enabling wheels to turn freely and playing a crucial role in the safety and handling characteristics of a vehicle. Made of precision-manufactured bearings, seals and sensors in one pre-assembled unit, a wheel hub bearing unit is critical to performance — from the smoothness of the ride, fuel efficiency and to the integrity of anti-lock braking systems. But you might say hub units are so expensive! What don’t people use these “value grade” units? Many manufacturers sell replacement hub bearings that are very low priced and may seem like a great value at first.
Unfortunately, with that low price, you’re going to get a low-quality hub bearing that is inferior to a premium, OE-quality hub bearing. The industry calls these hubs “value grade,” and experience has shown that these low-performing, value-grade hubs are no real value in the long run. In fact, many times these hubs last nowhere near what a premium hub does.
Another problem is their seals. A value grade hub’s seals can allow moisture and contaminants to enter and destroy the bearing prematurely. I mean, do you think your customer wants to replace a hub in as few as 10,000 miles? Some other problems? Value grade hubs can produce annoying wheel vibration and noise. They also can cause anti-lock braking systems to malfunction. And, in extreme cases, they can result in the wheel coming off — while the vehicle is in motion! Yikes!
So how do hub bearings affect braking safety? Hub bearings include the wheel speed sensor that controls the anti-lock braking system (ABS). This sensor sends a constant signal to the ABS control system, telling it how fast each wheel is turning. In an emergency situation, the ABS control system will determine if anti-lock braking is required. If the ABS sensor doesn’t work properly or fails, the ABS system fails, so the quality of this sensor — how it is made and protected from damage — is critical to braking safety. And a word about traction control.
You might wonder why hub bearings are critical to traction control systems? A vehicle’s traction control system uses a combination of electronic drivetrain controls in conjunction with the ABS system. Since it uses the same wheel speed sensors and components as the ABS system, it can be considered a subsystem and extension of that system. Together, anti-lock braking and the traction control system work to provide the driver with full control over the vehicle.