Which procedure must be done when servicing a wheel hub on a highway tractor equipped with antilock brakes?

When servicing a wheel hub on a highway tractor equipped with antilock brakes, it is critical to ensure that the speed sensor is properly positioned for accurate operation. Resetting the speed sensor depth is an important step because the speed sensor measures the rotational speed of the wheel, which is essential for the antilock brake system to function correctly. If the sensor is not at the proper depth, it may fail to provide accurate readings, leading to ineffective braking and compromising safety.

Ensuring the correct depth also prevents potential damage to the sensor, which can occur if it is too close to the tone ring or not in the optimal position. This procedure helps maintain the integrity of the antilock brake system, which is designed to prevent wheel lock-up during braking, helping to maintain steering control.

The other procedures, while related to antilock brakes, do not address the immediate need for correct sensor placement during a hub servicing task. Adjusting or replacing components like the tone ring or the wheel speed sensor would typically occur in other contexts, such as when replacing damaged parts or addressing specific fault codes, but they do not directly reflect the fundamental need to ensure proper sensor depth during routine hub maintenance.