National Odometer Day

• Buying a car? Be careful about odometer fraud. You’ve seen the above video. It should get you thinking about how easy it is to “roll back” a used vehicle’s mileage. It’s illegal, but some experts estimate that 1 in 10 cars have had their odometers tampered with at some point. For mechanical odometers, if the odometer looks crooked, jagged or jiggles when you hit the dashboard, it may have been tampered with. Tampering with digital odometers is just as easy and more difficult to detect. Be sure to ask to see the title so you can compare the mileage with what the odometer says and also check maintenance records, which will usually show a car’s mileage. Especially ask for a Carfax report or get the Vehicle Identification Number (VIN) and look it up on the Carfax website.
• Versions of the odometer may have been around since the time of Alexander the Great. Written accounts include highly accurate measurements of distances traveled by Alexander’s army that may have been measured with mechanical odometers. Actual descriptions of odometers date back to 27 BC and can be found in works by Vitruvius and Hero of Alexandria.
• The Chinese also had their own version of the odometer. It is believed to have been invented by the prolific scientist and inventor Zhang Heng in the late first century or early second century AD. It used the Chinese measurement “li,” which was approximately 500 meters. Like most odometers of the time, it was based on the operation of road-wheels of chariots.
• The first odometer for automobiles appeared in 1903. It was developed by Arthur P. and Charles H. Warner and patented as the Auto-Meter. It used a magnet and a rotating shaft to measure distances and also measured speed.

How Odometers Work

Most mechanical odometers have a flexible cable made of a tightly wound spring. It moves the numbers by spinning inside its protective housing made of a metal tube inside a rubber tube. On cars, the odometer also includes a gear that engages the shaft and turns the cable.

Computerized odometers use a toothed wheel mounted to the transmission’s output unit. As it rotates, it periodically interrupts the magnetic field produced by a magnetic sensor. With each pulse, it updates the odometer readout. That information is transmitted to the odometer display. In fancy computerized cars, the odometer is part of a network that can also display information like climate control information and give you access to controls like the power windows, radio and braking system.

Odometers Around The Internet

Need something special for your car, motorcycle or all-around uber-cool vehicle? Here’s a few from reputable dealers around the Internet.