I am having trouble navigating the formidable variety of cyclocomputers on the market.

I am not asking for product recommendations. A recommendation will in any case almost surely not be helpful. Each product seems to last very few years on the market. The barrier to entry is also small, and so many brands appear to be ephemeral, or at least have no distribution networks. And that's before noticing that during this pandemic even normally well-stocked and very large exercise/cycling stores routinely run out of stock in bike components.

The products backed by any sort of name-brand are many, and they are based (or at least have headquarters) in various places:

I'm after something quite modest, having a cadence meter in addition to speed and mileage. I've so far managed with just the last pair (and would gladly remain loyal to the well-built products from the Japanese maker, if I could spot a device for an upgrade), but on a road bike I like to think that there is something more that can be gleaned from knowing the "RPM" as well, especially since on a road bike I have access to speeds I could only until now dream of, and cadence seems to be the most critical point for keeping my knees healthy, and generally looking after the well being of my leg joints. I've eliminated the need for a HRM, as much as that can be helpful to push oneself and keep track of progress, because I don't think I will tolerate a firm chest band. This is likely going to be a separate product, possibly in the form of a watch from some Cupertino-based brand. (At the risk of digressing widely, I'll mention that even the last edition, the Apple Watch Series 5, which uses electric rather than optical sensors, may not function as a cycling heart rate monitor, since the second electrode is in the crown. Note that the two-electrode feature in the Series 5 produces not just a heart rate, but an electrocardiogram. Hence this watch may be an overkill for cyclists' need, in addition to not being usable unless one dismounts to manipulate the two electrodes. I'm not aware whether they kept the optical sensor while adding the electric ones.)

Now, someone who aims for the wireless option to avoid running cables all over the bike, will have the choice between a published (but not open/free to use) protocol, ANT+ (owned by Garmin), and closed, or at least proprietary, protocols, devised by the various manufacturers. An ANT+ sensor can only be replaced with another ANT+ sensor. Any other must be replaced with a component from the same manufacturer, and even then possibly from a specific line or for a specific product.

One intriguing recent innovation is in a (speed or cadence) sensor that comes in one part only. This is not just easier to install. It's also considerably easier to maintain, since there is no gap to worry about. Judging by these products coming from only one maker (Wahoo), this may well be patent protected, and so this feature is likely available only from that one maker.

Do the above few lines correctly summarize how a shopper can navigate the many products available in 2020? The innovations here are not that frequent, and so this discussion will likely remain relevant for a few years. It's puzzling that in other product categories very few makers eventually succeed in nailing how to build the right product. Yet in this arena it seems the competition is much more varied. As a shopper I oddly find that this variety is not at all helpful.

I believe I got all the details right. So basically this is a true/false question. Did you catch a mistake?

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    I'd eliminate any make that uses a proprietary protocol, since you will be stuck with their own sensors that may no longer be replaceable. With those that can handle ANT+ and Bluetooth you will always be able to add a sensor from a different make should one die on you. Also get a device where the batteries are user-replaceable, others do exist. – Carel May 30 '20 at 11:17
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    So, what's your question? "is this shopping comparison correct?" is probably not a great fit for the site. You might consider Bicycles Chat for a less-structured discussion. – Criggie May 30 '20 at 11:36
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    What's the point with "the Japanese maker" and "some Cupertino-based brand"? It's not like they're Voldemort and even Voldemort isn't real. – ojs May 30 '20 at 12:38
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    Big question is in 2020, 'What is a bike computer?' With the ability to connect to bike specific sensors, then you have to look every smart watch manufacturer as well. – mattnz May 30 '20 at 20:53
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    Please remove the update and ask as a new question. It may help you to understand how this site works if you Take the tour – mattnz Jun 4 '20 at 1:09

Heuristically, bike computers can be split into non-GPS and GPS computers. If all you want is speed, distance, and optionally cadence, your needs might be met with a cheaper non-GPS computer. Many of them have wires to a speed sensor mounted on the fork. In the past, some of these units may also have had wires to a cadence sensor by the cranks. An older wireless protocol for these exists (example product: the Cateye Padrone), but I'm not sure if wireless cadence sensors for this type of computer are widely available anymore.

In my view, an exact cadence measurement isn't critical for experienced cyclists. It is possible to train yourself to maintain a high cadence. If the concern is knee health, then I believe that strength and mobility exercises plus correct bike fit are probably a bigger priority than raw cadence (unless you have typically maintained very low cadence).

GPS units and connectivity

Entry-level GPS units are not that much more expensive than non-GPS computers. The GPS functionality can sometimes be useful, e.g. helping you navigate an organized ride that posts GPS files. You can arrange for the unit to upload your ride info automatically to sites like Strava. You can take or leave the informal competition and social media aspects, but the GPS data allow you to see where you went on a map and possibly plan alternative routes in the area, and it can allow you to log mileage more conveniently.

All GPS units can connect to both ANT+ and Bluetooth sensors. To my knowledge, most current GPS units have both ANT+ and Bluetooth capability. There are a panoply of sensors available. In principle, any sensor should be able to connect to any GPS unit (sometimes called a head unit), but sometimes there are specific incompatibilities. You may wish to check with the sensor manufacturer. For example, Wahoo says that (emphasis mine)

Wahoo cycling sensors are designed for use on any cycling computer that is able to accept an ANT+ or Bluetooth 4.0 (or newer) connection.

Speed and cadence sensors

First, a GPS head unit does not need a separate speed sensor. It will measure your speed from the GPS functionality. However, this is arguably less accurate than a bike-mounted speed sensor.

You referred to a combination speed and cadence sensor, usually mounted by zip tie to the chainstay. You would mount a magnet on the rear wheel, and a magnet to the crankarm or pedal spindle. This type of sensor uses reed switches: when the magnet passes the sensor, it closes a switch and completes an internal circuit. The sensor records the frequency of the resulting electrical pulses. NB: almost all the non-GPS units I'm aware of rely on this type of functionality. The sensors involved can either be wired to the fork or they use an older wireless protocol (i.e. not ANT+ or Bluetooth).

You can also have standalone cadence or speed sensors that measure cadence or speed via accelerometer. You can Google the physics involved if you're interested.

The statement that only Wahoo makes these types of sensor is wrong. I know that Garmin and Lezyne do also. I believe that a number of lesser-known Chinese companies do as well. I have not checked if any of the other manufacturers on the list offer these types of sensors, but I would not be surprised if they do.

Categorizing GPS units

How can users categorize GPS units?

Entry level GPS units often are not compatible with power meters. For example, the Lezyne Macro Easy (MSRP US$80) has Bluetooth connectivity, but its description omits any mention of power meter compatibility. Similar units include the Wahoo Elemnt Mini and the Garmin Edge 25. They retain GPS functionality. The majority of all GPS units can accept power meter or heart rate monitor input, so this is a very limited differentiating point.

Some higher-end GPS units are explicitly aimed at providing better navigation functionality. Examples include the Garmin Edge 1030 and Wahoo Elemnt Roam. Because GPS head units are more specialized than cellphones, they usually lack the computing power and input interfaces necessary to help you navigate properly, but the trade-off is that their battery life is much longer. These limitations still apply even to GPSes with navigation functionality, but they are more able to display maps and re-route you to a pre-planned course than lower-tier units.

Regardless of tier, what would differentiate GPS units from different manufacturers? Most likely build quality and usability. Note that usability includes the software interface as well as how well the manufacturer maintains and updates the software. Garmin may have a past reputation for software issues. Wahoo's units are generally regarded as more user-friendly than Garmin, although Wahoo's mapping functionality lags Garmin's.

Other types of sensors

You didn't ask, but there are many other types of sensors you can link to a head unit. The list is not exhaustive because I'm not even aware of all the stuff you could link.

  • Power meters are the most common other sensor you'd link to a head unit (NB: almost all have integrated accelerometer-based cadence measurement, and the few that lack accelerometers will use reed switches and magnets)
  • Muscle oxygenation sensors, e.g. Humon
  • Tire pressure sensors, e.g. Quarq Tyrewiz
  • Heart rate monitor, usually chest strap, e.g. Wahoo Tickr
  • Possibly you can link a smartwatch and its optical heart rate monitor to the head unit, but I haven't investigated
  • Lights: Garmin units can remote control some specially designed lights. In principle, the ANT+ protocol for lights is open source, but it may be non-trivial to implement, and I am not aware of other head units that have implemented it. For example, I am certain that Wahoo has not yet done so. Lezyne may have a separate protocol.
  • Rear-facing radar: the Garmin Varia is a radar linked to a light that warns the user of incoming rear traffic and transmits the signal to a head unit. The protocol for this is open source. Garmin units have this functionality. Wahoo recently implemented it as well. I have not investigated, but other companies may also have implemented this.
  • Cameras, e.g. GoPro units.
  • Electronic shifting systems can be linked to the head unit to display gearing or battery information. Shimano Di2 does require a separate wireless transmitter, but SRAM eTap or AXS do not. I believe but haven't confirmed that Campagnolo EPS has wireless function integrated into its latest version.

Other miscellany

A side note about non-GPS units: some ultra-distance races in remote areas may require you to have a non-GPS unit on your bike. These types of races will often hand out paper cue sheets at checkpoints, and you must arrive at a checkpoint by a certain time to be allowed to proceed on the course. In my subjective opinion, some organizers give off an attitude that seems snobby and retro-grouchy to outsiders. However, for these rides, you may not have reliable GPS reception. You will need an accurate distance measurement to use the cue sheets. In addition, many of these events want to conceal the route from the riders so that some of them don't arrange for external logistical support; this levels the playing field among all riders. Last, there's always the possibility that you a GPS unit could run out of power.

  • A quick sequel question: is it an option to connect a pair (speed + cadence) of Wahoo, Garmin, or Lezyne sensors to a smartphone, perhaps paired to a shrink-wrapped mobile app from the same vendor? – Sam May 30 '20 at 22:41
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    @Sam I am not familiar with this as I have a head unit, but it appears that at least Garmin have that functionality. www8.garmin.com/manuals/webhelp/cadencespeedsensors2/EN-US/… – Weiwen Ng May 31 '20 at 0:29
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    I can use my Garmin watch to broadcast its HR data to my Garmin Edge during an activity – Paul H Jun 2 '20 at 20:28
  • Great answer, but I doubt that magnets are sensed by reed switches in bicycle computers and such; I'd think that Hall-effect sensors, which sense magnetic fields, or inductive sensors, which sense changes in magnetic fields, would be much more likely to be used instead. Those sensors are much more rugged and reliable over the long term than reed switches, and probably cheaper too. – rclocher3 Jun 3 '20 at 18:49

Wireless bicycle computers have more problems than wired. The transmitter battery is much more expensive. Passing under high voltage power lines can reset the computer. Outside radio interference can confuse the computer.

For the few the bicycle computer companies you listed, Cateye has been making bike computers the longest. Since the 1970s.

Most new smart phones and fitness watches have acceleromters built in and that can provide more accurate speed and distance data than GPS and it works in doors, in caves, under bridges and every where on the planet. There are parts of the world that GPS does not cover.

People believe their smart phones to be the ultimate in data collection devices. They can store all the waypoints from a ride to upload to Strava and other maping sites and software. A low cost app on a smart phone can do what most traditional bike computers do and so much more. They can include mapping and turn by turn voice directions. A handlebar mount for the phone and an app will cost less than many bike computers and you still have your phone for other tasks like weather radar and finding the nearest tavern.

For all bicycle computers that use wheel mounted magnets for the sensors, mounting the magnet and sensor on the back wheel will be more accurate. The front wheel weaves side to side as a rider steers to maintain balance and so it covers more ground than the bike or rear wheel.

Most bike computers allow the user to input the wheel size. Some to the nearest centimeter, others to the nearest millimeter which can be up to 10 times more accurate. Many have preprogramed tire size options but those are just general estimates as each tire size will not be exact. Air pressure, rider skill in riding a straight line and rider weight will affect the accuracy.

Event time cut offs at certain check point is purely about logistics. When the organizer has to provide support, it's quite unreasonable to ask volunteers to wait at those check points for many extra hours or days to accommodate the slowest of participants. Most of these events are races so there is some expectation of speed. The SPOT tracker is a commonly used or required device. It uses gps to collect location data and transmits such data to earth orbit satellites every 5 minutes and is forwarded to central computers for evaluation and mapping on the internet. The Spot units also include an SOS button for emergencies. Some models include pre-set outgoing text messages.

Lasty, possibly the most important sensor on your bike could be the accelerometer in your helmet. The one that detects that you crashed and instructs your phone to call 911 for you. Just don't disable your location tracking. Your average speed or distance traveled becomes really useless information at that point.

We have too many cyclists getting run over by auto drivers too focused on their electronic devices, why add distractions yourself. Pay attention to the world around you instead of a screen and stay alive longer.

  • Very incisive comments. Re safety: A cyclocomputer can also be a safety guard. In one instance I recall that the wheels that I had thought were perfectly true at the occasional 45-50kph, were in fact far from it once I hit 65kph (downhill). I felt one wheel might fly off. Hence a speedometer can act as a deterrent: cross your prior peak speed, but only in small increments, also to test the quality of your reflexes. – Sam Jun 1 '20 at 22:54
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    How exactly does speed and distance tracking based on cell phone accelerometer work on bikes? – ojs Jun 2 '20 at 9:38
  • @ojs good point. The accelerometer should track steps but not your cycling speed and position. However, maybe the Op meant the phone GPS. – Weiwen Ng Jun 2 '20 at 21:11
  • Almost the same thing. Adding to the confusion, at least Suunto has algorithms that do quite decent job of tracking position using accelerometer and gyroscope when walking or running, but they depend on the walking motions to work. – ojs Jun 3 '20 at 8:50
  • Great start - keep up the good work! – Criggie Jun 3 '20 at 20:36

Yes, several.

To start with, "I'll mention that even the best designed smartwatches may not help much as a cycling heart rate monitor, since the second electrode is in the crown." is so nonsense it's not even wrong. There exists an entire category of non-smartwatch sports watches that use optical sensor, not electrode, for heart rate.

In addition to ANT and possible other proprietary protocols, there are open Bluetooth profiles for heart rate, cycling speed and cadence, cycling power etc. I would not call them secret or proprietary, but there are reasons why Garmin sellers don't tell you about it. Also, with wireless sensors you trade the hassle of setting up cables to the hassle of replacing batteries or charging sensors.

Also, you somehow managed to miss Suunto from the list of manufacturers.

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    However, heart straps (even cheap from Aliexpress) are much more accurate than the optical sensor on my TomTom. Hence, I often carry a compatible strap, most of the time one does not really notices it. Even in sports where one moves the uper body much more. – Vladimir F May 31 '20 at 7:19
  • Yes, the chest strap is more accurate, but that doesn't make the claim that wrist HR has electrodes in watch face and crown any less ridiculous. – ojs May 31 '20 at 7:31
  • I’d ask you to refrain from calling the OP’s assertions ridiculous. It’s possible to make the point that the OP is wrong without going ad hominem. – Weiwen Ng Jun 2 '20 at 22:49
  • Normally I'd have been more polite, but the idea is just too much over the top. To start with, you can't detect electric field from heart with two electrodes at one wrist. On the other hand, if you see a sports watch in person or even in a photo, you'll notice that there is the thing with LEDs and apertures that might be an optical sensor. If you read any product descriptions, they will tell the same thing. And last, there's the detail that the other electrode would be in watch crown even though most sports watches don't have one. – ojs Jun 3 '20 at 8:46

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