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Bicycle computers, speedometers and cyclometers

A basic bicycle computer (cyclometer or cyclocomputer) will indicate the bicycle’s speed (speedometer) and distance traveled (odometer). More sophisticated units can give information on temperature, heart rate, pedaling speed (cadence) and road slope angle (incline).

Bicycle computers, speedometers and cyclometers

More information isn’t always better. Too much information can be distracting, causing the cyclist to be less aware of road hazards.

Popular brands include Cateye, Strada, Sigma, Schwinn and Blackburn (Delphi, Neuro).

How Bicycle Computers Work

A magnet is fixed to a bicycle spoke. A sensor is triggered once every time the magnet passes by as the wheel turns. The sensor needs to be close to the magnet, a few millimeters. Mounting the sensor too far away is a common cause of malfunction. A shim may be required to position the sensor closer to the magnet.

The diameter or circumference of the wheel is entered beforehand into the computer. From this, the computer can calculate the bicycle’s speed and distance traveled. Because this calculation is straightforward, most cyclometers will have the same basic accuracy, limited by how accurately the wheel’s dimensions have been measured. Cyclometers will differ mainly in durability, waterproofing, display clarity and features.

Wired Versus Wireless Cyclometers

Wired and wireless cyclometers are similar. The difference is whether wires or a transmitter is used to send information from the sensor to the computer.

Wired cyclometers are cheap and reliable. A basic unit costs between $10 and $30. The main drawback is having to run wires from the sensor to the computer.

Wireless cyclometers cost more, about $50 for a basic unit. One drawback is that two batteries are needed, one for the sensor and one for the computer. There are no messy wires but interference is possible from:

Bicycle computers

neon lights
power lines
some electronic bicycle lamps
spark plugs (if mounted on a motorcycle)

Both wired and wireless units have limited range between the sensor and the computer, often 2 or 3 feet (wired units are limited by the length of the wires provided). This is enough for most situations unless the sensor is on the rear wheel, such as with a bicycle hooked up to a trainer.

Basic and Advanced Cyclometer Features

Basic cyclometers will display:

Current speed.
Average speed.
Maximum speed.
Total distance (odometer 1).
Resettable trip distance (odometer 2).
Resettable trip time.

Advanced cyclometer features include

Low-battery indicator.
Automatic power on and off.
Automatic pause during short stops (doesn’t affect average speed).
Support for 2 or 3 different bicycles. Selecting bicycle 1, 2 or 3 will select the wheel size. Odometers can be separate for each bicycle (example: road bike, mountain bike) or combined. A separate mounting kit is needed for each bike.
Remembering of settings between battery changes. Or enabling re-entry of odometer setting after a battery change resets all settings.
Heart rate display with chest strap monitor or wireless connection to popular third party wristwatch monitors.
Cadence display (pedaling rate) with second magnet sensor for pedal crank.
Temperature display (not accurate if cyclometer is in the sun).
Slope incline measurement (using built-in barometer to measure height).
Integration with power meters (Power Tap, SRM, Polar)

How to Choose a Cyclometer Display

bicycle gps

Cyclometers should be tested outdoors, under conditions similar to how they will be used. Sunglasses can make some displays hard to read. Polaroid sunglasses can cause streaks on the display to appear.

A large display allows information to be seen at a glance. Most displays show the current speed in larger numbers. Some cyclists may prefer to highlight cadence or other information instead but this isn’t always possible.

Most displays show 2 lines of information. Additional information is automatically rotated in and out of the display, or manually rotated by pushing a button. Some displays show 4 lines of information so less rotation is required, but the display becomes more cluttered.

A backlight is useful when cycling at night. Some backlights automatically turn off after a few seconds and cannot be kept on. The cyclometer can also freeze the display when the backlight is on. This makes it easier to read, but updates are not shown.

The refresh rate of the display should not be too slow. A noticeable lag between changes in speed and updates in the displayed speed, is annoying.

Cyclometers can display speeds in increments of 1 mph or 0.1 mph. Some use 0.5 mph increments, which can also be annoying.

The Best Bicycle Computer

Watching the miles pile up on the odometer can be strangely addictive, encouraging even casual cyclists to exercise more. A basic cyclometer will be enough for most cyclists. More information can mean too much time looking down instead of looking up at the road for hazards or enjoying the scenery.

Serious athletes can make the most of the more advanced features such as cadence display. Cyclists should also consider a GPS cyclometer.