Review (ette): Garmin Accessories

Garmin vivosmart HR
Garmin vivosmart OPTICAL HR

After you’ve bought your Garmin sports watch you can splash some more cash on one or more of the many, often highly useful, accessories.

Not all accessories will work on all Garmin models so you need to first check compatibility.

All Garmin sensors are ONLY ANT+ compatible, not Bluetooth. ie they will NOT work with many SMARTPHONES (some smartphones have ANT+…check).

I’ll say what I think about them as I’ve used them all and give you some Garmin alternatives.

Here is what you can get:

  • Heart Rate Monitor/Strap (optical, advanced metrics, underwater)
  • Footpod (instant pace and/or cadence)
  • ANT+ USB Stick (replacement for comms)
  • Speed and/or cadence Sensors
  • Power Meter
  • Power Pack
  • Handlebar and/or tribar-mount

Heart Rate Strap

These are not cheap. Your best bet is to buy one bundled with the original unit, often for a very small additional cost. Whilst the battery may well last you a year; IMO a strap+POD should last you 3+ years. The strap comprises a physical elasticated and adjustable ‘strap’ which has sensor pads to touch your skin. Then there is a clip on pod which sends the HR signal to one or many receiving devices. This clip-on pod may also do other exciting things such as detect and interpret movements such as your running cadence.


There are 4x iterations of the strap HRM1 (hard strap), HRM2 (‘premium soft strap that’s not great) and the HRM3. The HRM4 strap comes in 3 flavours HRM4-RUN, HRM4-SWIM and HRM4-TRI. You can guess the uses for each of these by the name. If you just run you buy the HRM4-RUN and if you just swim you buy the pool/lake-suitable HRM4-SWIM. the HRM4-TRI does it all, with the exception of lacking the chlorine resistance and super body adhesion of the HRM4-SWIM.

Garmin HRM4- SWIM & -TRI

HRM4-TRI and -SWIM both cache underwater HR data and later re-broadcast to the watch. Looking at your wrist underwater you will see a blank HR field – so it will not work for diving.


The HRM4-RUN and -TRI both provide the clever advanced running dynamics if your watch is able to handle that specific additional data. Garmin HRM straps will provide HR data to pretty much any Garmin watch and that will also be beat-by-beat RR data for HRV.

Problems: Generally the material straps will fail before the pod. Erratic readings are likely the fault of your strap. The hard plastic HRM and the new HRM4s seem good. The last iteration of the HRM3-RUN strap also seems to have good longevity.

Alternatives: There is no direct alternative to the HRM-TRI or HRM-SWIM. You might consider 4iiii Viiiiva or Wahoo TICKR-X. There is no alternative as a source for running dynamics although the TICKR-X will produce these metrics in the WAHOO app (also Bluetooth!).


Garmin are making forays into optical HR with a Fenix3 HR (2016) variant and also with running watches and the smart-band VIVOSMART HR. Only go for optical HR if you understand the benefits and pitfalls.

Note that all current and future Garmin optical watches are likely to also be able to connect to a normal chest strap as required.

Note also that the VIVOSMART HR wristband can be a source of optical HR for your Garmin sports watch on the other wrist. So you could use a VIVOSMART HR on one wrist with a 920XT on the other…if that’s your thing.

Optical HR is unlikely to deliver RR/HRV quality in 2016.

Problems: Inaccuracy. One more device to keep charged.

Alternatives: Personally I wouldn’t buy the VIVOSMART HR. Try the proven MIO LINK.

Speed and Cadence Sensors.

If you have a modern power meter it probably already provides cadence if mounted anywhere other than the rear wheel hub. Similarly a modern indoor turbo trainer will provide power, cadence and speed. Naturally a modern GPS watch will give you speed. So many of you will wonder why these extra sensors are needed.

Unfortunately not everyone has all this modern ‘stuff’ and so, compatibility permitting, the additional sensors can provide some or all of the data sources you are missing.


Garmin Speed, Cadence and GSC-10 Combined Sensor
Garmin Speed, Cadence and GSC-10 Combined Sensor

The classic Garmin GSC-10 (part: 010-10644-00) is a CHAIN-STAY mounted sensor that detects the passing of two magnets; one on the wheel (for speed) and the other on the crank arm (for cadence). This is a highly reliable unit in my experience with battery life of WELL over two years with at LEAST 3 hours use a week. It’s a pain in the derriere to install on my TT bike, less so on other bikes, and is VERY hard to change from bike to bike. However, once installed in place, it is extremely accurate and reliable. The GSC-10 does not know the wheel (tyre) circumference, it just detects revolutions. So you need to set the circumference in the watch/cycling computer otherwise the non-GPS based speed will be wrong. Various calibration methods will be used on various watches. Some have auto calibration.

The GSC-10 was ‘replaced’ in 2014 with the bike speed AND bike cadence sensor (part: 010-12104-00 owner manual link). Bands are used to fasten the speed sensor to the rear wheel hub and the cadence sensor to the crank arm. Position on the crank is unimportant. Set up of these is VERY easy. The data is accurate and your bike is very slightly more aero than with the GSC-10! You only need to get the sensor you require (speed 010-12103-00 or cadence 010-12102-00 or both 010-12104-00) and you can switch them between bikes very easily. The only downside I can see is that if the band deteriorates over time then you lose your sensor(s). Having said that the Garmin bands that hold the sensors on have 3 points of failure, so you should receive due warning before all 3 break.

Sensors are ‘waterproof’ to 1ATM or 10m. This means in reality that they are ‘highly’ splash proof and should not leak. I have heard reports of some that do but have never had that problem in many years of cycling.

Alternatives: Save up and buy a power meter to get cadence as well. I like the Garmin speed sensor. Wahoo make excellent alternatives and there are many NON-Garmin branded version that appear to be near-identical to the GSC-10.

Power Packs

The power pack for the Edge 810 is part: 010-10644-02. This can add about 20 hours of ride-time and comprises a solar charge and multi-country mains adapter. A battery is charged which in turn can be used to charge your device. So you can charge the battery whilst backpacking with solar panels on your rucksack and then leave your FENIX3 on charge all night from that battery.

Alternatives: Cheap USB battery packs abound for £/$5 or less. You’ll be lucky if you can charge whilst using your watch (check).


Foot pods are useful for indoor running on a treadmill, when you are under heavy tree cover or in a tunnel. Garmin running and triathlon watches are RUBBISH at showing your current/instant running pace. If you want to know how fast you are running NOW; then your MUST buy a footpod. I have 3! I use footpods EVERY time I run (outside or inside).

Footpods are best left to auto-calibrate over time (others will disagree). If you are performing a manual calibration it is best to run at the speed at which you intend to use the footpod (eg race pace).

Alternatives: These are expensive but invaluable bits of plastic. My advice is to stick with Garmin for these but others disagree.

Power Meter

Garmin sell the VECTOR power meter (v1, v2 and one sided versions). This are good but over-priced.

Alternative: Favero bePRO or Powertap P1.

ANT+ dongle

Garmin seem to be moving away from ANT+ communications with the PC. Instead they favour a USB connection with a proprietary cradle OR WIFI a BLUETOOTH SMART (v4) connection to your smart phone.

On that basis an ANT+ dongle is not much use except as a replacement.

You might however consider a USB dongle as a means of letting a PC convert your indoor bike’s trainer-speed into watts and then acting as a virtual/proxy power meter and sending it back to your top of the range triathlon watch or cycling computer (via the dongle). .

The images above show various flavours of ANT+ dongle. To be honest they are all fine to use and I’ve never had problems with any. Probably ones from other manufacturers are equally as good. I’ve never had cause to try one. Prices can vary significantly. I wouldn’t pay more than £10 myself. The micro one is quite handy for portables as it’s hard to snap when in use as it’s so small.

Other Accessories

Other accessories such as rear lights/proximity radar or action cameras are available as well as other even more obscure accessories.

Anyway if you found any of this info or info on the site useful please make your next purchase through one of these links…standard prices.

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1 thought on “Review (ette): Garmin Accessories

  1. Nice article about Garmin accessories!

    With regards to Footpods: The footpod from Adidas (part of the miCoach bundle is ANT+ and compatible with Garmin watches.

    On eBay you are able to find cheap used sets of those miCoach Pacer bundles. In connection with a marware sportsuit the perfect fit.


    Just to avoid the high price from Garmin.

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