Western-Star

Wheels: Dr. P. of Centerville asks, "I have an older BMW that has a navigation system. I recently saw a navigation system that used voice commands. Is it possible to upgrade my system through a software change to include this feature?"

Halderman: Most factory navigation systems can be updated to include new points of interest (POI) and streets. However, the voice command feature would require that a speaker and associated circuits be added, making the upgrade either very expensive or impossible. If the vehicle is equipped with a hands-free cellular telephone, the microphone may already be installed. BMWs, like some newer vehicles, use a communications network to operate almost all electrical and electronic components. The switches, such as the wiper switch, are simply a signal sent to the closest electronic control module. From the module, the request is sent through the communications network to the wiper module, which then operates the wiper motor. This means that there is more to it besides a software change to achieve the upgrade you would like to see.

Wheels: This sounds very complex. What can Dr. P. do if he wants a voice command navigation system?

Halderman: Dr. P. could check the BMW forum on the Internet for details about what upgrades are possible.

Wheels: Dr. P has another question, "My old BMW has been a lot noisier than in the past. I know tires can be the cause, but they were recently replaced. A friend said that a bad wheel bearing can be the cause. Is this true and, if so, how can I tell if the noise is caused by the tires or a wheel bearing?

Halderman: Good question. Noises are one of the most difficult faults for a technician to locate. In this case, determining if the noise is caused by a tire(s) or a wheel bearing is relatively easy.

- If the noise is the same on all types of road surfaces, then the most likely cause is a wheel bearing.

- If the noise changes while driving on different road surfaces, then the tires are the most likely cause.

According to automotive engineers, about 80 percent of the tire noise is transmitted through the chassis to the interior, leaving about 20 percent of the noise heard through the air. Wheel bearing noise is mostly transmitted through the chassis and is very similar to a noisy tire.

Wheels: Does replacing wheel bearings cost a lot?

Halderman: It depends on the type and location of the wheel bearing. Many wheel bearings are included as part of the hub assembly, while others are a simple replaceable part. Shops and dealers can give you an estimate after the diagnosis has confirmed the cause of the noise.

James D. Halderman is an ASE-certified master technician and the author of 12 textbooks. Submit your automotive care questions to Halderman via e-mail at jhalderman2@juno.com, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.