April 14, 2014 (cycling)
Wahoo RFLKT and Strava

Original Post

This device is awesome if you like using your iPhone as your cycle computer. I sold my Garmin Edge 305 on eBay and bought this little device instead. So far I love it. I recently started using Strava to view and analyze my rides, mostly because it does such an excellent job at motivating you to improve your performance over segments of your ride. It automatically breaks up your ride into segments (you can also create your own) and then rewards you with medals and recognition when you climb the ranks and improve your own personal records. A great motivation, especially if you mostly ride alone. I also bought a Polar bluetooth heart rate monitor to use in the gym with my iPhone. I liked the Polar because it also works with many workout machines so you can see your heart rate constantly during the workout. However, it does not offer ANT+ compatibility, so I couldn't see my heart rate on my Garmin any more! (my Garmin HR strap broke) So what I ended up doing was using the Garmin Edge 305 on my bike to see speed, elevation etc. and my heart rate monitor and iPhone in my back pocket to record the ride. Not the most streamlined of setups. Enter the Wahoo RFLKT+ I decided to buy the '+' version because of the improved elevation data from the built-in barometer. It was about $130. Since I sold my Garmin for $80 on eBay, it was a $50 upgrade... The idea is that it does four things over low-powered Bluetooth 4.0:

  • acts as an LCD display for your iPhone's cycling app (many cycling apps can now display on the RFLKT)
  • source of accurate elevation data (the iPhone has to use maps to determine elevation and is not nearly as accurate)
  • bridge between ANT+ devices and your iPhone
  • controls the iPhone's music (start/stop) and also controls your workout on your iPhone (start/stop)

This means that you can now keep your phone in your back pocket with the display off, and use the RFLKT+ as a front-end to your iPhone throughout the whole ride! I tried out three different apps on my iPhone:

  • Wahoo's Fitness App - rudimentary cycling app with some good customizations for the pages on the RFLKT+
  • Strava - You can display some basic information, but cannot configure the RFLKT screens
  • Cyclemeter - fully fledged cycling computer with excellent customizations and syncs to Strava when your ride is complete.

I ended up liking Cyclemeter the best since it captures the most complete information, and I trust its elevation data smoothing algorithm more than the others, although it seems like it records about 10% less ascent feet than I see from Garmins. Also, the total feet climbed data on cyclemeter seems different from the total feet climbed once you upload your data to Strava... so there is definitely some Strava magic that is applied on the uploaded data. From this week-end's ride, for example, I saw the following:

  • 3,050 ft - from most Garmins (510 and 800) who did the same ride
  • 2,213 ft - from the RFLKT+ recorded on Cyclemeter
  • 2,622 ft - on Strava from my data uploaded to Strava from Cyclemeter (both .fit and .tcx file formats)

Tracking the resolution to this conundrum on the Strava support site

UPDATE 4/18/2014

OK, I did 4 calibration rides back to back.  Exact route 4 times. With a combination of Strava, Cyclemeter and Wahoo Fitness on my iPhone, with and without the RFLKT+ display.  I also uploaded some of the TCX files to Garmin Connect.  The results are shocking!

Ride #RecordedProcessedAscentDistanceLink
1Strava, no RFLKT+Strava Web1973.1http://www.strava.com/activities/131591431
2Cyclemeter, with RFLKT+Cyclemeter Web1793.11http://tinyurl.com/mgtp89l
Strava .FIT1973.1http://www.strava.com/activities/131597181
Strava .TCX (edited to use device)2423.1http://www.strava.com/activities/131610744
3Wahoo Fitness, with RFLKT+Strava Web2773.1http://www.strava.com/activities/131601357
Garmin Connect (TCX)2243.16http://connect.garmin.com/activity/482330359
4Strava, with RFLKT+Strava Web1983.2http://www.strava.com/activities/131606223

I have no idea who to believe!  These are massive differences. But just looking at the ride, I started at 100ft, climbed to 235ft, then down to 145ft and back with a slight climb back to 115ft at the end, so it should be at least (235-100)+(235-145)+(115-100)=250ft.  So the Strava corrected calc is too low... maybe the Wahoo with the RFLKT+ is the most accurate!

UPDATE 4/19/2014

I think I should return the RFLKT+.  I do not believe the elevation data coming from the RLKT+... I looked at some of the elevation data recorded by the RFLKT+'s barometer, and it is incredibly jagged .  +5m and -5m regularly from point to point, which is completely impossible for a smooth climb.  When looking at the data coming from a Garmin device , the elevation data is much more realistic. At this point I feel that the RFLKT+ just has a very poor barometer in it.  Bad data in = bad data out. I logged a support request with some of these observations on the wahoo site... let's see what happens:

The altitude data coming from the RFLKT+ looks way off. I am attaching the files uploaded from the app. I climbed a very even climb, and if you look at the "disp_altitude" field in the attached cdv file (same information in the GPX file...) there are these massive jumps... (6m in a second!) in some spots:
51.967692 <<<<<< 
This distorts my ascent information greatly. Is this a defect in the barometer? I bought the RFLKT+ instead of the RFLKT mainly because of wanting more accurate ascent information in my rides. The information, when uploaded to Strava, for example, is way off from others who ride with Garmins, for example.

UPDATE 5/16/2014

OK, I am now happier with my RFLKT+ using Cyclemeter and uploading to Strava.  The new release of Cyclemeter fixed the TCX upload to have the right device type so that Strava uses the altitude information from the RFLKT+