Size of Car Speedometers

Car speedometer sizes can vary, but most range from 3 1/8 to 3 3/8 inches. Other units have dimensions of 4 x 7.8 x 6 inches.

Overview

The speedometer is the instrument used to measure the speed of a car. It has a built-in display to indicate the results. The importance of this feature cannot be overestimated. It lets you know how fast you are going and if you are still within the speed limits. It is able to determine how quick the vehicle is by assessing the ground speed.

Development

Although various speedometer sizes have existed since the early 20th century, it was not deemed a requirement. It was after 1910 that the device became a fixture in cars. While their designs vary, their position has rarely changed. They are always placed close to the driver. Most are set at the back of the steering wheel.

Design

Many of the units sold today are digital. These display 2 or 3 numbers to indicate the speed. Other systems need a rotating arm. With these models, the arm goes from high speed on the right and low speed on the left. The device displays speed in miles and/or kilometers.

The maximum speed it can display depends on the product. Aside from cars, the device is also used in trucks, motorcycles and even airplanes. In planes, the device is known as an airspeed indicator.

Its equivalent in boats is the pit log. Older models have about a 10% error tolerance. Newer models have much lower levels thanks to improved technology.

Most of these devices work via a cable linked to the vehicle’s transmission. This indicates how fast it is going. The electronic variants are fitted with field sensors and magnets to indicate the drive speed. On bicycles, the device determines the time between the wheel revolutions.

Calibration

Calibration of the speedometer is performed on vehicles when they are constructed. This is necessary to authenticate the device’s output with the vehicle’s actual speed. The device is set to match with the pinion and ring ratio and tire dimensions.

A magnet is used to determine the speedometer’s value. The drive and gear ratio must be taken into account as well. A vehicle can only be mass produced if the calibration is correct.

Because its role is so vital, the speedometer sizes are crucial. They should be large enough for the driver to see. As stated earlier, the placement is also crucial.