Bicycle odometer

Category: Archive Sports and Fitness

What is it for

There are many people who frequently get on a bicycle, both for sport and as a daily habit. For example, many use two wheels to go shopping, run small errands or – the luckiest – even go to work. The bicycle odometer is a small device that can be useful to all regular two-wheel users, from amateur athletes to simple amateur cyclists. Naturally, for professional athletes and for those who seriously dedicate themselves to this activity, the odometer is an indispensable accessory. There are numerous types of bicycle computers on the market, ranging from the simplest, equipped with basic functions, to the most technological and multi-parameter. The former can be considered as useful gadgets, while the others are expensive devices that contain many functions within them, sometimes quite complex. For the non-professional cyclist it is a small satisfaction to be able to monitor travel times, know how many kilometers you have cycled or the maximum speed reached. The odometer can provide all this information and more, and by spending just a few tens of euros you can purchase a model suited to your needs.

How does it work

The operation of most odometers is based on small magnetic devices capable of counting the number of revolutions made by the front wheel. To do this, a small magnet is attached to one of the spokes of the wheel, while a sensor is firmly attached to the fork. At each revolution of the wheel (or, in simple terms, every time it makes a complete revolution), the passage of the magnet is recorded by the sensor and the impulse is sent to a small computer which is fixed to the handlebars. The odometer is based on the previously set value relating to the wheel circumference and, based on the information transmitted, is able to calculate the distance travelled, the speed and other parameters depending on the specific characteristics of the device. The transmission of impulses can take place via an electric wire or, in more advanced odometers, be wireless. In order for the parameters reported by the odometer to be correct, it is essential to enter as accurate a measurement as possible of the wheel circumference. To do this, you need to mark on the ground the lowest point where, for example, the cap of the inner tube is located and, once you get on the saddle, pedal until the wheels make a full revolution. In order to obtain a precise measurement it is best to carry out several tests and then calculate the arithmetic mean; to carry out these measurements it is always better to get help from another person. It is important that the measurement is extremely faithful to reality, given that apparently infinitesimal deviations can turn into large errors over long distances. Much less empirically, higher-end odometer models are integrated with a small database that allows you to automatically set the circumference measurement based on the parameters of the wheel mounted. The same information can be obtained from the shop where the wheels were purchased or directly from the manufacturer.

Main functions

Here are some of the functions that can be found on an odometer or cycle computer:

  • instant speed : it is one of the most interesting pieces of information, and allows you to maintain a constant pace;
  • average speed : it is calculated on the basis of the instantaneous speeds recorded during the entire journey;
  • maximum speed : it is the recording of the highest speed reached. This parameter is fundamental for example for those who practice downhill;
  • pedaling cadence : measures the number of pedal strokes per minute, and is a parameter that allows you to choose the right ratio to maximize pedaling efficiency;
  • total distance (odometer): allows you to know how many kilometers have been travelled, a very important parameter for planning training sessions. This information is essential to know where you are when, for example, you travel along unknown roads following the directions of an itinerary;
  • partial distance : it is useful for the reasons described in the previous point but also to keep track of particular distances from one point to another or traveled in a unit of time;
  • watch : an obviously very useful function, which allows you to leave your wristwatch at home;
  • stopwatch : allows you to record the total time and, sometimes, also the partial times (such as, for example, lap times). With this parameter it is possible to plan workouts based on changes of pace capable of developing muscles and cardiovascular power. Many models are also equipped with a start/stop function and only measure the time actually spent in the saddle;
  • altimeter : measures the altitude at which you are and must be set before each use since atmospheric pressure conditions can vary from one day to the next. Many odometers store the distances of the route and allow you to calculate total and partial height differences.

Some odometer models are also equipped with an automatic shutdown function which, when not in use, saves battery life.

Which one to choose

Basically, choosing the "right" odometer depends on individual needs. For the city or occasional two-wheel user, a model that is capable of carrying out the basic functions, i.e. the calculation of the total distance travelled, the time taken and the speed, both instantaneous and average, may be sufficient. At the other extreme we find the odometers used by professional cyclists or those who practice triathlons which, for example, are equipped with a stopwatch capable of keeping in memory the partial travel times or the times of each lap of the track, in addition to the measurement of the pedaling cadence and, in some cases, even a GPS and an altimeter. Some of these models are even equipped with a system that warns the cyclist if his pedaling cadence is above or below average. For specific needs you can consider purchasing models with particular characteristics. For example, road cyclists who train in a group can choose particular models of wireless odometers whose pulses are transmitted with an encrypted signal that prevents their device from "reading" by mistake the signals sent by those of their companions. For those who love mountain biking, there are specific odometer models for this type of sporting activity and which allow accurate reading even when the speed is very low, for example on the most demanding climbs. Some odometer models are made of very light materials, and are essential when every single gram of extra weight can affect their performance. This feature is indispensable for some professionals, but for the majority of two-wheel users the weight of the odometer is absolutely irrelevant.


However, odometers, especially those in the lower price range, have a certain margin of error that must be taken into account. For example, when traveling along a mountain dirt road or, on the contrary, an asphalted stretch, the difference in friction can cause the alteration of the measurements. The same happens when the road surface is wet, or when the cold causes the "contraction" of the wheel. However, these are minimal differences, completely irrelevant for the majority of cyclists. Although odometers are designed to withstand different weather conditions, not all of them are able to withstand heavy rain and in this case it is best to refer to the specifications in the instruction booklet. To avoid unnecessarily discharging the battery and ruining the device, the odometer should never be left under direct sunlight if not in use. Most odometers are mounted on a support that allows you to attach and detach the device according to your needs (and of course to avoid theft or vandalism). It is not essential to equip each bicycle you use with its own specific odometer: you can in fact purchase models that can be used on all types of bicycles. This choice is particularly suitable if during the week you usually ride a city bike, while on weekends you use a mountain bike for some trips to the countryside or mountains. Finally, a word about safety. The statement "the more functions, the better" is not necessarily valid: if the odometer is too complicated or excessively redundant with information, you run the risk of becoming unnecessarily distracted during the journey and finding yourself in dangerous situations!

Published: 2011-11-16From: Redazione

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