A bicycle computer ( Swiss Velocomputer ) or bicycle speedometer is an electronic device for the continuous measurement of speed and the distance covered while cycling . Almost all cycle computers have additional functions, such as displaying the time and cadence .
With the advent of cycling , the desire arose to receive data on distances traveled and speeds achieved , especially during training . Simple mechanical solutions that were then developed were odometers and bicycle speedometers .
With the odometer , a driver attached to the spokes increased a counter by one count with each revolution. Since the distance covered with each wheel revolution is equal to the circumference of the wheel, suitable odometers were offered for different rim diameters. An inaccuracy resulted from the fact that tires with different rolling circumferences can be mounted on rims with the same diameter. Most odometers were attached directly to the front fork of the bicycle. Despite the large distance from the driver's face, most odometers were readable while driving. These mechanical counters were sometimes called cyclometers .
Mechanical speedometers , which also indicated the speed, were a further development . Here a transducer was attached to the axle of the front wheel, which was connected to the display unit usually attached to the handlebar by a flexible shaft with the transducer. These speedometers were also offered to match the rim size. The display unit was mostly the same for all wheel sizes, only the transmission ratio of the drive or transducer was adapted to the wheel size. Some models had a trip meter in addition to the odometer. Mechanically driven speedometers are still available today as “retro” items in various designs for common tire sizes.
With the development of microelectronics and LC displays , small computers with low energy consumption for mobile use could be produced from the 1980s. At that time the first cycle computers came on the market. The functional principle has remained the same in most cases to this day: A small magnet on a spoke induces a voltage pulse in a coil attached to the fork; alternatively, the spoke magnet triggers a magnetic switch . This signal is forwarded to the display unit, the actual computer. In the past, this was done exclusively with the help of a cable, since around 1995 (with an increasing trend) wireless systems have also been offered. The latest generation of bike computers uses coded digital signals that are hardly susceptible to electromagnetic interference. The pulses are counted electronically, processed and finally displayed in the desired units. The devices no longer need to be produced for a specific wheel size, as the wheel circumference can be set with millimeter precision.
The advancing development of electronics made it possible in the 1990s to incorporate numerous additional functions. Average speed and top speed are now standard.
Other common functions are:
- the measurement of the cadence via a sensor attached next to the crank
- determining the altitude above sea level (usually using a barometric altitude measurement )
- the measurement of ascent or descent including a summary of the altitude meters traveled
- the measurement of the heart rate via a chest strap
- the estimation of the energy consumed by the driver based on the heart rate, taking into account the gender and body mass of the driver
- the time display
- the display of the temperature
- the use of two bicycles with separate mileage and travel time counters
- The possibility of data storage and transfer to a PC , creating new ways of evaluating training.
The rolling circumference not only depends on the specified rim size (e.g. 26 or 28 inches), but also on the tire width, because the wider a tire, the higher its sidewalls. The following values can be used as a guide:
|Tire size (according to ETRTO )||Tire size (inch)||Circumference (mm)|
|47-305||16 * 1.75 * 2||1272|
|40-406||20 * 1.5 * 2||1527|
|47-406||20 * 1.75 * 2||1590|
|37-540||24 * 1 3 / 8A||1948|
|47-507||24 * 1.75 * 2||1902|
|23-571||26 * 1||1973|
|40-559||26 * 1.5||2026|
|44-559||26 * 1.6||2051|
|47-559||26 * 1.75 * 2||2070|
|50-559||26 * 1.9||2089|
|54-559||26 * 2||2114|
|57-559||26 * 2.25||2133|
|37-590||26 * 1 3/8||2105|
|37-584||26 * 1 3/8 * 1 1/2||2086|
|20-571||26 * 3/4||1954|
|32-630||27 * 1 1/4||2199|
|28-630||27 * 1 1/4 fifty||2174|
|40-622||28 * 1.5||2224|
|47-622||28 * 1.75||2268|
|40-635||28 * 1 1/2||2265|
|37-622||28 * 1 5/8 * 1 3/8||2205|
|18-622||700 * 18C||2102|
|20-622||700 * 20C||2114|
|23-622||700 * 23C||2133|
|25-622||700 * 25C||2146|
|28-622||700 * 28C||2149|
|32-622||700 * 32C||2174|
|37-622||700 * 35C||2205|
|40-622||700 * 40C||2224|
GPS devices that are only slightly larger than wristwatches have been around since 2002 . The regular determination of the position enables the display of the basic data, i.e. the speed and the distance covered. Often the height is also displayed, but due to the principle it is quite imprecise. Better models have a more precise barometric altimeter. A recording is used to evaluate the journey later. Some outdoor GPS devices can also receive, display and record data from different sensors (speed, cadence, heart rate). If there is not a sufficient clear view of the sky due to buildings, trees, tunnels, etc., GPS reception may be significantly impaired and data may be corrupted or not available. GPS devices with stored maps compare GPS data with the map data and thus achieve sufficient accuracy.
Smartphones and PDAs
Some smartphones and PDAs are also suitable as bike computers with the appropriate software , equipment (especially GPS) and optionally with a cadence sensor. However, these devices are usually not protected from rain and often only have a short battery life. You should therefore pay attention to energy-saving functions when selecting the software. The runtime can be extended by taking additional or external batteries with you. Corresponding brackets are available from specialist retailers for secure attachment to the bike that is also protected from rain. As an additional function compared to dedicated bike computers, some apps for smartphones offer the display of the course of the trip on maps, navigation along recommended bike routes can be carried out, and the routes taken can be recorded. If necessary, a training computer or a heart rate monitor should also be carried for the pulse recording and the calculation of the energy expenditure.
- Michael Gressmann, Franz Beck, Rüdiger Bellersheim: specialist knowledge of bicycle technology. 1st edition, Verlag Europa-Lehrmittel, Haan-Gruiten 2006, ISBN 978-3-8085-2291-2
- Fritz Winkler, Siegfried Rauch: Bicycle technology repair, construction, production. 10th edition, BVA Bielefelder Verlagsanstalt GmbH & Co. KG, Bielefeld 1999, ISBN 3-87073-131-1