Revision as of 15:03, 9 April 2017

The Garmin Fenix 5X is the top of the range of Garmin's running/outdoor watches. It has an impressive array of features, and it uses high quality materials to achieve a high-end look. It's only real weakness is its rather mediocre GPS accuracy, though this can be easily remediated by combining it with the Stryd. Of course, all this comes at a fairly hefty price, as the Fenix 5X retails for $700 (plus $200 for the Stryd.) Note: I'm still writing this review, so please consider it early access to my initial testing results.

1 Support This Site

Please support this site This review was made possible by readers like you buying products via my links. I buy all the products I review through normal retail channels, which allows me to create unbiased reviews free from the influence of reciprocity, or the need to keep vendors happy. It also ensures I don't get "reviewer specials" that are better than the retail versions.

2 Which Version?

There are four versions of the Fenix 5, one of which is branded as the Forerunner 935. (The 935 is a plastic bodied Fenix 5 for $100 less.)

Within each model, there are choices of wristband type, with a metal wristband adding $150 and sapphire glass adding $100. There are also a number of color choices, though the 5X is only available in gray. So, which to buy? I'd recommend getting the 935 as it's cheapest. The only reasons to buy the Fenix version are if you need maps (5X), WiFi (any with Sapphire glass), you want the Fenix look, or you want the smaller size of the 5S. Of course, with the release of the Fenix 5, you can get the Fenix 3 at a lower cost. The Garmin Epix is also worth considering as it has the maps of the 5X, but Garmin has stopped releasing firmware updates and it's nowhere near as attractive.

3 The Big Questions

For a simple evaluation of a GPS watch, I look at how well it can answer some basic questions. There are many things a runner might look for in a running watch, but I feel these four questions are critical.

• How far did I run? This is the most basic question, and the Fenix 5X has rather mediocre GPS Accuracy. For me, this amount of error in the distance would be unacceptable. For instance, on a 20-mile Long Run you could see an error of nearly a mile, which is enough to really mess up your training. The good news is that the Fenix 5X has great support for the Stryd footpod that gives awesome accuracy.
• How fast am I running? Knowing how fast you're running can be a nice to know, or it can be vital for your training or race performance. Because of the nature of GPS, watches that rely on GPS signal alone tend to have serious problems with current pace. The poor GPS accuracy of Fenix 5X tends to exacerbate this, with readings fluctuating by over a minute/mile regularly and up to two minutes/mile occasionally. So, if you want pace information you need to get a Stryd footpod.
• Where am I? The Fenix 5X has about the best navigation options available. The headline feature is the full color, preloaded maps. On top of this, there is a breadcrumb display of where you've been, the ability to load predefined courses, navigation to waypoints, backtracking your course, a magnetic compass, and an altimeter. A larger display would be nice, and I'd love to have this functionality with the Suunto Spartan Ultra's high resolution display and touchscreen, or the Leikr1's huge display, but the Fenix 5X does pretty well.
• What's my cadence? Cadence is one of the most critical and often overlooked aspects of running. If you get your Cadence right, many other things naturally fall into place. The Fenix 5X will get Cadence from its internal accelerometer, as well as from a Footpod, or the Running Dynamics heart rate strap/pod. There are alerts for Cadence, which is great, and even a metronome feature. I don't think it comes any better than this.

4 The Fenix 5X for Ultrarunning

The Fenix 5X claims 20 hours of battery life, and I tested it under optimal conditions and managed to get 23 hours. That's tough to achieve in the real world, as you have to avoid using the map display, backlight, or changing the display too often. With the map display in constant use, I was still able to achieve the rated 20 hours, which is pretty good. This makes the Fenix 5X a great candidate for shorter races (50 miles/100k). But if you hope to be still moving during the Second Dawn, then there are probably better options. You can charge the Fenix 5X on the run, but the position of the charging cable means you can't wear the watch while you're doing so (unlike the Garmin Fenix 3.) See Watches for Ultrarunning for more details.

5 Physical Characteristics

The Fenix 5X is a big watch, and it's larger than I'm comfortable with as a 24 hour/day activity tracker. However, on the run it fells okay even on my diminutive wrists. The watch straps rotate where they connect to the watch body, unlike the Polar V800 where they extend from the watch body and therefore don't conform as well. The materials are excellent quality, and while it doesn't have the simplistic elegance of the Suunto Spartan Ultra it's still very nice. The exposed bolt heads make the Fenix 5 look rugged and sporty, though it's a bit fussy visually. The only thing that feels a little cheap and tacky is the watch strap itself on the cheapest version. It's nothing like the silky smooth and soft watch material that Suunto use.

6 GPS Accuracy

I've tested the GPS Accuracy of the Fenix 5X with its initial release firmware, and it's possible that its accuracy will improve as the firmware matures. (I tested using the 4.20 version of the GPS firmware, which is included in the 2.40 version of the overall firmware.) So far, the Fenix 5X certainly has 20 of room for improvement. At best, the GPS accuracy could be described as mediocre, and I think it's bad enough that it could significantly mess up your training. If you look at the middle, curved section, you can see that the Fenix 5X is doing particularly badly here. This is a challenging section, and reveals any weakness in a GPS watch. The right most segment with the right-angle turn is a section of the most watches do reasonably well on, but the Fenix 5X is struggling here as well. The tracks don't look too bad, you can see that the Fenix 5X is not able to calculate the distance correctly. The Fenix 5X doesn't get too badly confused going under the bridge, actually looks a little better in that area than the two Suunto watches shown for comparison. The blue lap markers are rather widely spread, again giving more evidence of poor GPS accuracy. It's possible that other versions of the Fenix 5 might have different GPS accuracy. It's possible that the plastic 935 might do a little better, but without testing it's impossible to know. (I buy all my test gear through retail channels. This allows me to be brutally honest in my reviews, as I don't need to keep the manufacturer happy in order to continue getting free samples or early access. The downside is that I'm more limited in the array of watches I can test. Therefore, it's unlikely that I will test other versions of the Fenix 5 at this point.)

The GPS tracks from the Fenix 5X. This diagram has tracks color coded with green indicating good accuracy through to red indicating poor accuracy, and the lap markers as blue dots.

For comparison, here are the tracks from the Suunto Spartan Ultra, which had appalling GPS accuracy when it was first released, but the latest firmware has improved things.

Here's how the Suunto Ambit3's accuracy looks.

As with all the watches I test, I first left the Fenix 5X in its "ready to go" mode with a clear view of the sky for over 30 minutes. This is to ensure that the chipset has ample time to download the almanac from the satellites, which should only take about 12 minutes. I also give the Fenix 5X at least five minutes after it has got a satellite lock before starting my run. This is to give it the best possible chance of having good accuracy. (Like most modern GPS watches, the Fenix 5X will download information on the satellite orbits when it's synced, but this predicted information is not as good as the live for data transmitted by the satellites themselves.)

7 Optical Heart Rate Monitoring

I've not found any Optical Heart Rate Monitoring (OHRM) implementation that's good enough to be useful, and the Fenix 5X is no exception. I believe that you're better off having no heart rate data than bad heart rate data. While a chest strap based heart rate monitor can have accuracy issues, these are generally dramatic and obvious, whereas OHRM can be quite misleading. (The issues with a chest strap heart rate monitor are also usually fairly easy to remediate, either with some electrode gel or a new battery.) The accuracy of Optical Heart Rate Monitoring (OHRM) will depend on a number of factors:

• The watch needs to fit just right. Because of the sensor is measuring the expansion of the capillaries with each heartbeat, too much pressure will prevent this expansion. However, to lose and the watch won't get a good reading due to lack of contact. Getting this tension just right can be tricky, especially if you're wrist expands or contracts over time.
• Movement seems to confuse OHRM systems, possibly because it changes the papillary filling. Some users have noted that their OHRM systems seem to lock on to their Cadence rather than their heart rate.
• Temperature seems to be a huge factor, and most systems work better in warmer conditions. If you're a little chilled, your body will restrict blood flow to your capillaries to retain body heat, making it much harder for the optical HRM. Of course, because the system needs to be against the skin, it can be tricky to use them in cold conditions. I've cut a hole in a arm warmer so that I can see the watch face while preventing frostbite to the surrounding skin.
• It's possible that bright sunlight might also influence the accuracy, though I've not noticed any obvious correlation.

While it's possible to compare the graph of heart rate data from the Fenix 5X with a chest strap, such an approach doesn't provide very much data. Instead, I've gathered over 10,000 data points and an analyzed them. The two graphs below are taken during my runs with the Fenix 5X. The graph on the left plots the heart rate from the optical HRM of the Fenix 5X against a chest strap based reading. All of the points should lie along the pale green line, which represents the optical HRM reading the same as the chest strap. The two red lines represent an error of 25 bpm, and the blue line represents the regression line. The graph on the right is a distribution map of the errors. As you can see, the Fenix 5X optical HRM is a fairly close for a good portion of the time, but overall there are a lot of bad readings.

I thought that perhaps the Fenix 5X would do better when I'm not running. After all, it's able to read my heart rate continuously, so even if the optical HRM is useless for running, I wondered if it might be valuable for evaluating my activity the rest of the day. I was rather surprised, and more than a little disappointed, to learn that the Fenix 5X seems to do even worse when I'm sedentary than it does when I'm running.

I had rather limited hope that the Fenix 5X would be of any use overnight, but it actually did surprisingly well. I suspect that the darkness and the lack of movement made things a little easier for it. It's also possible that a much lower heart rate is easier to lock on.

8 Comparison Table

I evaluate running watches in three distinct ways. Firstly, you can use a watch on its own, without any kind of Footpod. This is probably the most common way runners use their watch, but you miss out on a lot. The second rating is with a standard Footpod that is available quite cheaply. These Footpod's can be reasonably accurate once the calibrated, but calibration is a little tedious. The final evaluation is with the Stryd Footpod, which is vastly more accurate than any other type of Footpod, or and more accurate than GPS. The table below looks at the score, and the value for money of each watch for each of the three conditions. (I’ve also tested the Apple Watch 3, but I’ve not included it in these tables as it’s not really a running watch.)

The score is the sum of how well each watch can answer the four basic questions (how far, how fast, where are you, what's your cadence), plus some bonus points.

1. The "How far you've run" will be based on GPS only for "without Footpod" and "with Standard Footpod", but based on Stryd if supported in the "with Stryd Footpod" table..
2. How fast you're running assumes you're using a Footpod if it's supported, otherwise the rating is 0-2 based on GPS accuracy.
3. The "Where are you?" is based on various navigation features such as back to start, breadcrumbs, and preloaded maps. For some watches, you have to turn GPS off to get the benefit of Stryd, so those watches have worse "where are you scores" with Stryd than without.
4. The cadence score uses 1 point for an internal cadence sensor, 2 points for footpod support, 1 point for support from chest strap cadence, and 1 point for cadence alerts.
5. I give 1-2 bonus points for application support, 1-2 bonus points for data upload, 1-2 bonus points for Optical Heart Rate Monitoring, and 0-1 bonus points for battery life.
6. Value for money is the score divided by the price (at the time I last updated the table.) Your needs may be different, so you might weight the different aspects of the watches differently, or be basing your decision on different criteria totally. Hopefully this table will give you a good starting point for your decision.

8.1 Score Breakdown without a Footpod

8.2 Score Breakdown with a Standard Footpod

8.3 Score Breakdown with a Stryd Footpod

8.4 Basic Features

9 Navigation Features

For "navigation":

• Color Maps gives you full color maps, rather like a smart phone, with roads and paths marked out.
• Track Outline is a display of where you've run, rather like a breadcrumb trail. If there are maps, the outline is superimposed otherwise this is just the outline on its own without any context.
• Course Outline is an outline of a route that can be downloaded. I've found this useful during ultras or in unfamiliar cities where I've needed to know where to go.
• Back To Start is a simple arrow point to your starting point, so it won't help you backtrack.
• Back To Waypoint returns you to a previously marked location using a simple arrow to point.
• Compass. A magnetic compass can help you orient yourself or the map. Without a magnetic compass you have to be moving for the GPS to give you a sense of direction.

(Older Reviews: Polar RC3 GPS, Soleus 1.0, Motorola Motoactv.)