Garmin Speed & Cadence Sensors V2 with ANT+/Bluetooth Smart: In-Depth Review


In the highly unlikely event that you didn’t get enough Garmin news today with the announcement of two brand new head units (the Edge 530 and Edge 830, see reviews at those links), you’ve also got yourself some new sensors to toss on the to-read pile.

This post will be part ‘finally!’, and part ‘as expected’. Today Garmin finally announced dual ANT+/Bluetooth Smart variants of their magnetless speed and cadence sensors, which had previously been ANT+ only. An update was somewhat expected however, given Garmin’s announcement of a dual ANT+/BLE heart rate straps three months ago. The goal of all these new sensors is making it easy to use them with apps like Zwift or TrainerRoad on smartphones, or Apple TV.

However, what might be unexpected here is that the magnetless speed sensor actually has a bit of a party trick: It can record rides even when you don’t have an app or device actively connected to it. Yup, the little pod gained a brain and can now remember any rides you complete sans-GPS, transferring them to Garmin Connect (or even Strava) afterwards – perfect for bike commuters.

I’ve had media loaners of both sets of pods for…well…a lot of months now, so plenty of time to get into the details and nuances of how they all work (actually, way…way…way more time and detail than I ever wanted to know). Once I’m done with the flotilla of them that I now have, I’ll get them back to Garmin here in the new feature – and most likely go out and get my own to equip some of my bike fleet here. But more on my plans a bit later.

Oh, and typically I don’t release in-depth product review threesomes all at the exact same second on this site. But, sometimes things planned for one time period get shifted to an entirely different period. Thus, a threesome happens. Today’s that day.

What’s in the boxes:


I like simple boxes. Because it means I get to write less text and focus on eating more cookies. Starting with the speed sensor box, it’s grey – like the weather outside my window here in Amsterdam:


Inside here’s what you’ve got after shaken onto a table.


First, there’s a small manual. It explains how to use a rubber band twelve times. Once for each of the twelve language sits written in:


Next, there’s a small safety guide. It also repeats everything twelve times. Specifically it tells you not to eat the batteries, and to consult a TV technician if your cadence or speed sensor isn’t working. Really, I’m not kidding.


Oh, and then there’s a bag with the speed sensor itself. This is it:


Next, there’s the cadence sensor box:


And the stuffs inside:


It too has the exact same paper stuff. In fact, it’s the same manual and safety papers for both.


Except unlike the speed sensor, you get two baggies here. One includes two rubber bands, depending on your crank arm size. If you’ve got a large crank, you’ll use the larger rubber. If you’ve got a smaller crank, you’ll need a smaller rubber (and maybe an oversized truck to compensate).


And then here’s the cadence sensor all in put together. It looks super similar to Garmin’s past magnetless sensor, albeit an itty-bitty-bit different in terms of some slants.


Oh, and if you happen to buy the combo box? Yup, all the exact same stuff in a single consolidated box – saving the world an extra box an an extra set of manuals telling you how to consult TV technicians and use rubber bands:


And now my unboxing job is done. Overkill, yes. Unnecessary, absolutely. But done.

How it works – Speed Sensor:

We’ll start with the speed sensor first. Getting it installed requires either consulting with one of the twelve language iterations in the manual, or, using common sense. You can choose to install it on your front or rear wheel hub. If you install it on your rear wheel hub, then it’ll work while on most trainers (assuming your wheel stays on your bike of course).  In my case however, my rear wheel has a PowerTap power meter hub in it. As such, there’s some known magnetic interference there – so I just stick it on the front wheel instead:


The same is true of our cargo bike which I’m also using it on – since the rear wheel is simply too big for it.




And what if your rear wheel hub is too big for the band (as was my other commuter bike)? Well, in that case I just used a secondary rubber band. It’s hardly ideal, but it does work.

In any case, with all that done you’ll want to pair it up in Garmin Connect Mobile. You’ll go to add devices in the app, and as long as you’ve rotated your wheel a few times to wake it up, it should find it immediately.

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Next it’ll ask for the tire size and even will allow you to enter what’s written on the sidewall exactly as its written:


It only takes a second to add it, which then will show up in the devices menu, and allow you to tweak some settings, notably your weight and wheel size. Also, you can check for firmware updates and see the battery status, as well as learn about the sensor indicators:

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Now, before we get to this sensors little trick – let’s take a step back and talk a more normal configuration – pairing it to a bike computer. Here’s it paired as an ANT+ sensor to a Garmin head unit. Simply go into the sensors menu and either search for all sensors, or more specifically search for just speed sensors. Then add it (add the ANT+ variant if available, so you don’t eat up any of the Bluetooth channels, as there’s unlimited ANT+ channels but only two Bluetooth Smart channels):




You can specify your wheel’s circumference, which is required for it determining distance. Alternatively, Garmin head units (and most others as well), will automatically calculate the wheel circumference if left blank, using GPS. So on your next ride, usually about 1/4th to 1/2 a mile later it’ll give you a little pop-up message that says “Wheel size calibrated”. I’d recommend doing this on roads where the GPS signal is good. Don’t do this at the start of a trail-head on a bunch of switchbacks.


Now, since the main thing of this sensor over others is the ability to see it via Bluetooth Smart, here’s it is with a Suunto Spartan Trainer:


And just fine with the Wahoo Fitness app:

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In fact, like Garmin’s new HRM-DUAL, this device supports two concurrent Bluetooth Smart connections (plus ANT+). Thus in total sensor can sustain three+ concurrent connections:

A) ANT+: It can sustain an unlimited number of connections via ANT+
B) Bluetooth Smart #1: The first available Bluetooth Smart connection channel
C) Bluetooth Smart #2: The second available Bluetooth Smart connection channel

Of course, the main reason you’d use this sensor is to display speed and distance on your bike computer, most likely off-road. For the most part, GPS is more than accurate and stable enough these days on-road for most cyclists.  Whereas off-road mountain-biking in dense forest or with switchbacks, that’s where you’d probably want a speed sensor to give you better distance accuracy and better pace stability.

But Garmin decided to add a unique feature to this new speed sensor that gives it ‘value’ for on-road cyclists: Offline caching of your workouts.

This feature means that the sensor will automatically start a new workout (sans-GPS) every time you start pedaling. And then a few minutes after your bike stops moving, it’ll end the session. This is super interesting for bike commuters that may not really care about starting a GPS session for their daily rides, but are interested in the totals being accounted for.

So I did exactly that – I put the sensor on our cargo bike, which I use as my day to day getting around town bike and how we get the kids moved around the city (we don’t have a car, it’s Amsterdam after all).

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This meant that every time I went somewhere it’d simply record the ride. No need for me to open an app on my phone or bring a Garmin GPS device along.  After the ride it quietly saves the file, but doesn’t sync it to your phone until the next time the sensor wakes up. So for most people that means your morning ride to work would sync in the evening when you started pedaling.  Of course, you can always go wake up the sensor and sync it whenever you want.  This results in rides that look like this in Garmin Connect Mobile:






In fact, these rides are also transferred to platforms like Strava too. The only downside I suppose is if you use your bike a lot during the day for errands as I do – this is what your day looks like. A random Friday in my case:




Which in turn means I had all these also in Strava. These are considered legit workouts from a file standpoint, no different than a 5 hour ride.  My suggestion to Garmin would be to allow me to set a minimum distance threshold for sync to 3rd party services. Just don’t sync those.


Garmin says they’ll consider it, but that in the meantime you can turn off the activity creation bit altogether if you want. Or, you could just disable the pairing to Garmin Connect Mobile. Either way.

Still, it’s a cool solution – and honestly, I’d love to see Garmin consider expanding it.  For example, what if that sensor actually activated GPS on your phone and recorded the GPS track. Just like Fitbit’s ‘Connected GPS’ feature’. Obviously that’d be user configurable, but again for bike commuters it’s one less step than having to start/stop a GPS session. Being able to just have it track that in the background would be nice – and likely not a huge hit for most people with short commutes.

Accuracy-wise I’ve been doing some longer concurrent rides with both the speed sensor and GPS side by side. Obviously, that’s somewhat imperfect because if I’m talking a 50KM ride, then I don’t truly know which is which. In this case though, I’m looking for it to pass the sanity test, which is to say that it should be ‘really darn close’, and not something wonky. Typically when I’ve seen magnetless sensor issues, the wonky is readily apparent in either looking at the files, or the resultant cumulative distances.

For fun, here’s Sunday’s ride:


Now, what actually happened there is that we stopped our GPS devices at the train station, then ran like hell to make the train (rolling the bikes next to us). Since the sensor is accelerometer driven, it actually never went to sleep – even on the train due to the bumps and us occasionally moving the bikes around to accommodate people.  So it then recorded the distance post-train ride, as I rode home.

So if I stop the distance at the same point as when I stopped the other units, here’s what I’ve got:

Garmin V2 Magnetless Speed Sensor: 58.53km
Garmin Edge 530: 58.52km
Garmin Edge 830: 58.47km
Polar Vantage V: 58.67km

Of course, there’s also some nuances there too. I rode a few hundred extra meters before I started the Edge devices which the sensor accounted for. So I tried to zap that from the beginning too by looking for the paused time.

Here’s how speed overlaid on that ride between the Edge 530, Edge 830, and speed sensor. Neither the Edge 530 or 830 were paired to the speed sensor. The speed sensor was simply doing its own thing and then synced the ride to my phone after the fact:


And, if you want to dig even further into the data fields, here’s the distance accumulation over time (also in my data set), which shows that the units are evenly adding distance. The Vantage does some weird data file stuff that hoses up the graph a bit with the dropouts, but otherwise, it’s following the same curve.


I’ve also down countless rides between my doorstep and office door, and ended up with near precisely the same distance each time. Given I usually take one of two bike paths the same exact way each time, it’s a pretty consistent test.  Though, I have been tempted to take the cargo bike out onto the local running track. But, I don’t think that’d be looked kindly upon.

How it works – Cadence Sensor:

Switching over to the cadence sensor, it’s even easier than the speed sensor. First, you’ll utilize those rubber band skills to attach it to your crank arm. The recommendation would be to place it on the inside of the crank arm, since that gives you a bit more protection from the outside of your bike where your shoe may swipe past it:


Note that it included two rubber bands depending on crank arm size. Also, do at least one rotation of your crank arm before you head outside, simply to validate there’s no clearance issues – especially if you have a super high-end triathlon bike with extremely low clearance to the frame. For this sensor you need 8.18mm of clearance:


Pro Tip: Always put it on your left crank arm.

Again, for 99% of bikes out there, that won’t be an issue. But for the 1%’ers, I included the info you need to know. Plus, you can slide the sensor closer to the bottom bracket if you need to – no issue there. Usually there’s more clearance down there.

Once that’s done, it’s time to pair it up to the devices of your choice. First up I gave it a whirl on the Polar Vantage V (wanting to differentiate as much as possible). No issues.


Here’s a ride using the Garmin cadence sensor with the Vantage V (but more on accuracy there in a moment):


And then meanwhile on Garmin for the cadence over ANT+ (though this unit can also do Bluetooth Smart):


I also did it via Bluetooth Smart on the Suunto Spartan Trainer, and that paired just fine. In fact, here’s the data from last month with it:


As you’d expect, you see cadence on your head unit while you’re riding. And, if you’re using a 3rd party app like Zwift, you’ll see it there too:

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So what about accuracy? At this point, things are all good. I had some initial quirks a while back that have since been resolved through the beta process (which, is what testing and beta processes are for).  As of the last week or so I’ve actually been riding mostly outside with it paired to a Polar Vantage V series unit. Here’s how the data compares side by side to the Stages LR (dual-sided) unit also transmitting cadence, in this case to an Edge 530:


However, that’s only a snippet of the ride. If I zoom back a bit and over to another section, then you’ll see there were some odd drops over Bluetooth Smart with the Vantage V:


The precision of those drops is odd. and I don’t know if that’s a Garmin or Polar issue. I haven’t seen any other drops on any other devices that I’ve tested with. So this is definitely a first. If I look at my previous Polar Vantage V ride on Friday, I don’t see any dropouts (below). While it’s plausible the dropouts aren’t actually dropouts, that seems unlikely given the near-precise nature of them happening at the exact same interval.


Again, not something I’ve seen with anything else I’ve tested – so really just a single ride artifact I think. Here’s a quick ride again, this time on Zwift via Bluetooth Smart, without any issues. In this case, I started off at normal cadence (80-100RPM), and then I slowly crept down to 21RPM, at which point it dropped out (as expected). Then I went all the way up to 180RPM steadily, no issues (obviously you’ll see slight single-second differences recording from four different head units, as normal). Here’s that data set:


In addition, towards the end I did some super quick spin-ups, upwards of 180RPM. In that case, we do see it overcommit towards 220RPM (well beyond what I can do, I usually top out in the 180RPM range). Though, seeing cadence issues at 180RPM isn’t unheard of, and frankly affects but a fraction of 1% of people out there.

Also of note was that I was recording the Garmin cadence on both the Bluetooth and ANT+ channels. The iPad for Zwift had it via Bluetooth Smart, while the Garmin Edge had it on ANT+.

As you can see, virtually identical.  Not that I expect any issues since this is basically proven tech just adding in Bluetooth Smart connectivity. However, there’s plenty of timing related nuances to broadcasting on any protocol, especially Bluetooth Smart, that can cause issues. The good news is those don’t appear to be an issue here.

(Note: All of the charts in these accuracy portions were created using the DCR Analyzer tool.  It allows you to compare power meters/trainers, heart rate, cadence, speed/pace, GPS tracks and plenty more. You can use it as well for your own gadget comparisons, more details here.)



I totally get it – sensors aren’t all that exciting. Especially ones that should have been released years ago. The good news here is that like the HRM-DUAL a few months back, these sensors become the baseline for new sensors included in various Garmin bundles. For example the new Edge 530 and Edge 830 units released today have these dual ANT+/Bluetooth Smart sensors in their bundled variants. That’s a lot better than ANT+ only sensors.  So ultimately, it’ll save you money in a bundle versus having to go out and buy a 3rd party sensor that costs more.

Still, we are seeing Garmin ever so slightly push the envelope here. Assuming one can envision an exciting manila sensor-laden envelope. There’s no other Bluetooth Smart cadence or speed sensor on the market that accepts dual Bluetooth Smart connections, let alone one that accepts dual Bluetooth Smart connections plus an ANT+ connection. So if you’re on something like a Polar or Suunto device and want to use Zwift concurrently, now you can actually do that….via Garmin products. Go figure.

Secondly, the automatic caching of rides in the speed sensor is cool for certain audiences – namely commuters. For most roadies or mountain bike folks, you’re probably going to have a head unit on the bike anyway. But for an around-town bike, it’s a nice little touch that you get your mileage added to Garmin Connect (and even Strava) each day.  The only downside is that if you use that around-town bike a lot each day (as we do), then it frankly kinda muddies the water a bit (again, you can turn it off if you want). Still, hard to complain about that.

If you’re in the market for new sensors for your bike, these seem like an obvious choice. Like the HRM-DUAL, Garmin is basically matching the competition and then adding in a tiny few extras that you’re like ‘Ok, it’s the same price, might as well just get this instead’. So while they’re (super) late to the party….at least they brought Timbits.

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Garmin Speed/Cadence Sensors (new ANT+/Bluetooth Smart ones)

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