Which computer, which numbers
A cyclocomputer calculates speed, distance and riding time from wheel revolutions or GPS position. This reference compares device types, matches sensors to riding goals and walks through the setup order: mount, set wheel size, pair.
| Device type | Measurement source | Sensor radio | Setup effort | Battery / recording | Typical numeric range |
|---|---|---|---|---|---|
| Wired cyclocomputer | Spoke magnet, fork sensor | None | Mount, enter 2110 mm wheel size | Replaceable cell | Speed from wheel math |
| Wireless cyclocomputer | Spoke magnet, wireless fork sensor | Proprietary 2.4 GHz or ANT+ | Mount, align magnet, enter 2110 mm | Replaceable cell | Cadence band 60–100 rpm |
| GPS head unit | GPS position | ANT+ and Bluetooth | Mount, pair each sensor | 12–20 h recording per charge | Speed from position |
| GPS + cadence | GPS position + crank sensor | ANT+ | Mount, pair cadence sensor | 12–20 h | Cadence 60–100 rpm |
| GPS + heart rate | GPS position + strap | ANT+ | Mount, pair strap | 12–20 h | Heart rate 120–180 bpm |
| GPS + power | GPS position + power meter | ANT+ | Mount, pair power meter, calibrate | 12–20 h | Power 100–250 W |
Choose by data source: spoke magnet, paired sensor or GPS position.
Wired and wireless units count wheel revolutions: a spoke magnet passes a fork-mounted sensor, and speed equals wheel circumference multiplied by revolutions per second. The wheel circumference — about 2110 mm for a typical 700x25c road tyre (ETRTO 25-622) — must be entered correctly or every distance and speed reading drifts.
GPS head units fix position instead, record rides as FIT files, a compact data format created by Dynastream Innovations and now maintained by Garmin, and advertise roughly 12 to 20 hours of recording per battery charge.
Sensor radio is the practical divider. Classic units use a reed switch on the fork; modern units pair ANT+ or Bluetooth sensors for cadence, heart rate and power.
Speed and distance come from wheel math; cadence, heart rate and power come from paired sensors.
Speed is wheel circumference multiplied by revolutions per second. Cadence counts crank revolutions per minute: a steady club rider pedals at about 80–90 rpm, and units typically display a 60–100 rpm working band.
Heart rate is reported in beats per minute, near 120–150 bpm for a club rider on moderate terrain and up to about 180 bpm at effort. Power is reported in watts — roughly 100–250 W sustained — and needs a dedicated power meter.
Each quantity has its own unit, so a screen showing rpm next to bpm next to W is reading three different sensors, not three views of one measurement.
ANT+ is a low-power wireless sensor protocol developed by Dynastream Innovations, a Canadian company acquired by Garmin in 2006.
Dynastream also created the FIT file format used by GPS bike computers to record rides; Garmin maintains the format after the acquisition.
Cateye, founded in Osaka, Japan in 1954, produced some of the earliest widely sold electronic cycle computers in the 1980s, which is why the spoke-magnet layout still looks the way it does today.
Standards matter when mixing brands: an ANT+ cadence sensor pairs with any ANT+ head unit, and a FIT file opens in most ride-analysis tools.
Only three dated milestones are on record for the protocols and makers referenced here.
Each quantity has its own unit, sensor and mounting point.
Protocol and format origins (ANT+, FIT) and maker milestones (Cateye, Dynastream, Garmin) as stated in the reference material behind this page.