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Verdict: 
An affordable power meter, but we didn't find it to deliver useable data
Weight: 
11g
Contact: 
Arofly power meter
3 10

The Arofly power meter is lightweight and affordable but we've found that it simply doesn't provide measurements that are consistent enough that it can be considered a useful training tool.

Arofly is unique in that it attaches to the valve stem of your rear inner tube. It's larger than a dust cap but is still very small with a 20mm diameter and a weight of 11g, including the CR 1632 battery that lives in there and the Presta adaptor (if you need one, see below).

> Buy this online here

If you use a Schrader valve the Arofly just screws directly on to it. The valve pin needs to make a good contact with an 'Air Post' in the centre of the Arofly, beyond the thread, in order for you to get readings.

If you use a Presta valve you need to loosen the valve screw, then tighten an Arofly adaptor in place – just a small threaded piece – and finally screw the Arofly on. Again, the valve pin needs to contact the Arofly's Air Post. I've used the Arofly with Presta valves and found that it works easily on some but not on others. You need to find an inner tube with a tall enough valve pin. Once up and running it has stayed up and running without dropping out.

Then you need to download the Arofly app, available free for both Android (OS 4.3 or later) and iOS (iPhone 4S, 5, 5S, 6, 6 Plus or later), on to your smartphone and pair the device with the app via Bluetooth. You input a few details: the units you want to use, the type of bike you're using – road, mountain or small wheel – and so on, and you're good to go.

The Arofly will not talk to other head units so you can't have the power figure displayed on your Garmin, say, you have to mount your smartphone to your handlebar/stem. A basic smartphone mount comes as part of the pack, although you'd get better security with something like a Quad Lock Bike Kit.

The app must be open and running while you ride. It gives you this information as you go:

* Current speed

* Time of day

* Arofly's battery status

* Cadence

* Power

* Ride time

* Distance

* Heart rate (if you've paired a heart rate monitor with the app)

* Cumulative ascent

There's just one display page and it isn't customisable. You can't, for example, have your power as a 3-second or 10-second average, and there's no auto-pause function – you need to do that manually if you stop.

Assuming you do that, the app gives you this info when you're done:

* A map of your ride

* Ride time

* Ride distance

* Average speed

* Average cadence

* Average power

* Calories burned

It also gives you graphs that show:

* Speed

* Power

* Cadence

* Heart rate (it you've paired a heart rate monitor)

* Ascent

Those graphs are small on a smartphone and you can't zoom in on them so you're better off pressing the 'Upload to Strava' button and viewing the information over there. If you like, you can then export a TCX file of your ride from Strava and transfer it somewhere else.

How does it work?

Okay, let's go back a bit: a power meter that attaches to your inner tube valve – how does that work? 

"Originating from aerospace technology, Arofly is the result of years of research and cooperation between aerospace scientists and sports biomechanics professors, developing a patented air pressure differential technology based on the pitot tube design," according to Arofly.

'Through core and patented algorithm and advanced calibration technology the precise pedalling power is registered and with that the cycling performance.'

Hmmm, okay. That doesn't reveal a lot. Like me, your first reaction is probably scepticism. How could it possibly work? Fitting strain gauges in a chainset spider, crank arm, pedal or hub: that makes sense. Fitting a power meter to an inner tube valve? It's a mental hurdle, to say the least. The big question is, does the Arofly provide useful power data?

We always review power meters by comparing the results from one system to those of others. It's difficult to say categorically that one is right and one is wrong, but we can look for discrepancies.

I've used the Arofly alongside a CycleOps PowerTap hub and a Stages crank-based system. The results I've got from the Arofly are very different from those I've obtained from either of the other two.

Take this ride as an example, where I've ridden a bike with the Arofly paired up to an iPhone and a PowerTap hub paired to a Stages Dash head unit. I've transferred the data from both devices to GoldenCheetah in order to compare the results. The power readings from the PowerTap are in green, the power readings from the Arofly are in violet.

Arofly v PowerTap graph.jpg

Arofly v PowerTap graph.jpg

What I did on this ride was warm up, then do four hill reps of about 5:50mins each, riding downhill and on the flat for around 3mins between each, then rode home. In other words, it was a structured workout with definite start/finish points for every section.

The first rep starts at 11mins, the second one at about 20mins, the third one at 29mins and the fourth one at 38mins.

The PowerTap data shows what I'd expect: four periods of power with very little effort as I went back to the start between each of them.

The Arofly data for the first rep is hardly distinguishable from the warm-up in the main, although there's one peak at the end of the interval. It does indicate that there was less power in the rest period between intervals, but with several peaks in there that I can't explain.

> Tour Tech 2017: Power meters of the peloton

The second interval is clearer, although I was aiming to ride it in a similar way to the first (and that was reflected in the PowerTap data).

The Arofly picks up the rest period after the second interval and then the work during the third interval, although the peaks and troughs don't track those from the PowerTap particularly closely. Then there's quite a big spike in the Arofly's data halfway between the third and fourth intervals. I really couldn't tell you what that's about because I wasn't pedalling at the time... And so on.

I rode the first two intervals seated, and stood up on the pedals at times during intervals three and four to see if that made a difference to the data. That seems to have resulted in higher peaks from the Arofly.

Even trying to be generous, it's difficult to reconcile the Arofly measurements with those of the PowerTap to any great degree. The power graph goes up during the work intervals (well, it does for intervals two, three and four, at least) and drops during the rest intervals, but this was a very defined session and you'd be hard pressed to discern that from the Arofly's data.

Conclusion

I'd love to be able to tell you that, against all odds, Arofly supplies power measurement that's good enough to train by, but my experience is that it doesn't. I've not managed to use it as the basis of training sessions because the figures are too inconsistent. Sorry.

The team behind Arofly says that development has been continuing over the past few months and that it jumped the gun in sending us a product back in March.

> Buyer's Guide: How to choose a cycling power meter

It says that any shortfalls in performance are down to the app, which is being improved, and will be addressed by the Arofly+ which is a rechargeable head unit that's designed to work with the valve-mounted device. The Arofly+ will be unveiled at the Eurobike cycle show in Germany in a couple of weeks.

The team says it has ploughed a huge amount of money into the development of the system and it really believes that it has a 'game changer' of a product here.

There will have to be big changes in the results before I could think of recommending this product.

Verdict

An affordable power meter, but we didn't find it to deliver useable data

road.cc test report

Make and model: Arofly power meter

Size tested: One

Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

The Arofly is designed to be an inexpensive power meter.

Arofly says: "Arofly is an epoch-making innovation in cycling power meter.

"By its patented brand-new technology and measurement, Arofly provides most affordable and most user-friendly Power Meter to benefit general cyclists.

"Arofly provides a state of the art power meter which displays overall biking data in real time, for people who enjoy cycling and may have their own Arofly, at a very affordable price.

"Arofly assists the biker ride right to achieve and complete their goal with perfection."

Tell us some more about the technical aspects of the product?

Here's the spec as given by Arofly:

Size: diameter 2cm

Weight: 10g

Bike compatibility: Road bike, Mountain bike, BMX...

Operating temperature: -30 °C to + 85 °C

Water proof, Dust proof

Battery type: CR 1632

Transmission: Via Bluetooth version 4.0; Frequency: 2.4GHz

Compatible Smartphone: iPhone 4S, 5, 5S, 6, 6 Plus or later Android Smart phone Mobile OS 4.3 or later

Rate the product for quality of construction:
 
4/10
Rate the product for performance:
 
3/10
Rate the product for durability:
 
5/10
Rate the product for weight (if applicable)
 
6/10

It is very light, but something like a Stages or 4iiii power meter adds only a few grams to the overall weight of your bike.

Rate the product for value:
 
3/10

It doesn't cost a lot compared with other power meters, but in my experience it doesn't give useable power measurement.

Tell us how the product performed overall when used for its designed purpose

Poorly.

Tell us what you particularly liked about the product

The price... but only if it actually provided useable data.

Tell us what you particularly disliked about the product

The fact that the data isn't consistent.

Did you enjoy using the product? No

Would you consider buying the product? No

Would you recommend the product to a friend? No

Use this box to explain your score

The Arofly gets some points for picking up general trends in power (mostly) but my experience is that this device just doesn't give data that's consistent enough to be useable for training by power.  

Overall rating: 3/10

About the tester

Age: 43  Height: 190cm  Weight: 75kg

I usually ride:   My best bike is:

I've been riding for: Over 20 years  I ride: Most days  I would class myself as: Expert

I regularly do the following types of riding: commuting, club rides, sportives, general fitness riding

Mat has worked for loads of bike magazines over 20+ years, and been editor of 220 Triathlon and Cycling Plus. He's been road.cc technical editor for eight years, testing bikes, fettling the latest kit, and trying out the most up-to-the-minute clothing. We send him off around the world to get all the news from launches and shows too. He has won his category in Ironman UK 70.3 and finished on the podium in both marathons he has run. Mat is a Cambridge graduate who did a post-grad in magazine journalism, and he is a past winner of the Cycling Media Award for Specialist Online Writer.

22 comments

Avatar
peted76 [798 posts] 3 months ago
8 likes

Disappointing. Also struggling to see how something which does not do what it is supposed to do can score 3 out of 10 for 'performance' and 3 out of 10 for 'value'...  if it doesn't work it doesn't work.. there appears to be very little 'grey area, lets give it a few points for generosity' here...

Avatar
barongreenback [114 posts] 3 months ago
3 likes
peted76 wrote:

Disappointing. Also struggling to see how something which does not do what it is supposed to do can score 3 out of 10 for 'performance' and 3 out of 10 for 'value'...  if it doesn't work it doesn't work.. there appears to be very little 'grey area, lets give it a few points for generosity' here...

 

Or even the 1.5 star rating. If it doesn't perform its stated function then how can it get any stars at all?

Avatar
mylesrants [390 posts] 3 months ago
1 like

Love innovation. Fair play to the company and a good first step. Look forward to see how it evolves into a  useable tool

Avatar
ROOTminus1 [17 posts] 3 months ago
3 likes

I understand that as you push on the cranks, there's a measurable 'bob' that can be read as a change in tyre pressure that can theoretically be calculated back to the power you lay down, but surely there are too many variables for it to be an accurate method.

Those erroneous spikes and troughs are possibly explained by road surface imperfections, and how does the change in pressure as tyres warm up affect the readings? I imagine a shift in body position, changing your front/rear weighting would be enough to throw this gizmo off.

Avatar
brakeforcake [1 post] 3 months ago
1 like

Even if this did work perfectly, wouldn't adding another 11 grams to your valve stem knock your wheels noticeably out of balance? 

Avatar
davel [1988 posts] 3 months ago
2 likes
ROOTminus1 wrote:

I understand that as you push on the cranks, there's a measurable 'bob' that can be read as a change in tyre pressure that can theoretically be calculated back to the power you lay down, but surely there are too many variables for it to be an accurate method.

Those erroneous spikes and troughs are possibly explained by road surface imperfections, and how does the change in pressure as tyres warm up affect the readings? I imagine a shift in body position, changing your front/rear weighting would be enough to throw this gizmo off.

...and if you've got decent souplesse, you're less likely to spike power on the downstroke.

This prompted a pretty entertaining debate when it first came in. I'm skeptical, but even if they can iron out these imperfections, it's a prototype at the moment, not a product.

Sending one to road.cc and one to DC Rainmaker (his only registered speed a few months back) suggests to me that they're going the tried-and-tested route of throwing anything out there and get enough suckers to stump up cash for it (see Limits and SpeedX).

Avatar
RobD [539 posts] 3 months ago
0 likes

I can understand how this might work for riding on rollers where you have a consistant and smooth surface and aren't likely to shift your position around all that much. I guess if the unit has accellerometers in it it might be able to tell that the change is due to bouncing on the surface but it'd be pretty hard going.

I'd love for it to work but I just can't get my head around how it's possible even if they do improve the app.

Avatar
IanMunro [29 posts] 3 months ago
0 likes

Air pressure in tyres is a red herring. It doesn't measure tyre pressure. The only reason that it attaches to the inner tube stem is so that  people think something magical is happening.
The unit will work equally well or more accurately equally terribly if you selotaped it to a spoke.

The unit contains an an air pressure sensor that measures atmopsheric pressure rather than tyre pressure. It also contains an accelerometer to detect wheel rotations. The device gives a power estimate by calculating your forward speed and acceleration combined with climb rate. It then uses an arbitary value for your cda and crr combined with your mass to come up with a power figure. At best it will give a result similar to strava estimated power algorithm.
The schematics are here -
https://fccid.io/2AJGD-AROFLY01/Schematics/Schematics-3197365
It will never produce anything better than you get direct from strava.

 

Avatar
notfastenough [3728 posts] 3 months ago
0 likes

Despite the poor review, I'm hopeful for this, because most of the issues sound like algorithm matters. I also wonder whether there is any learning aspect to the software, because the measurements do improve as the session progresses.

One fundamental challenge I can see, though, is the multiple actors on the air pressure. Road surface, such as cobbles or gravel, would change the air pressure regardless of rider effort, as might cornering. 

Assuming these things are ironed out, compatibility with different head units and this price point would be great. 

Avatar
hawkinspeter [1135 posts] 3 months ago
0 likes
mylesrants wrote:

Love innovation. Fair play to the company and a good first step. Look forward to see how it evolves into a  useable tool

I'm a neophile as well, but this seems like they tried to get it to work, failed and are now just hoping to get back as much money as they can. I doubt very much that this will be improved at all.

Avatar
hawkinspeter [1135 posts] 3 months ago
0 likes
brakeforcake wrote:

Even if this did work perfectly, wouldn't adding another 11 grams to your valve stem knock your wheels noticeably out of balance? 

Bicycle wheels don't really spin fast enough for balancing to be much of an issue. Apparently, you may be able to feel a 'pulsing' if you're going really fast and the wheel is very out of balance. There are some specific wheel weights that you can buy if you ever notice an issue. I don't think 11g will make too much difference to a typical wheel when compared to the forces needed to deform the tyres.

Here's Jobst Brandt's opinion on it: http://yarchive.net/bike/wheel_balancing.html

Avatar
Simmo72 [672 posts] 3 months ago
0 likes

interested to see if the quality of results improve on a turbo or set of rollers, that is where I would want to use a power meter, for focused , not out on the road.

Avatar
IanMunro [29 posts] 3 months ago
5 likes
notfastenough wrote:

Despite the poor review, I'm hopeful for this, because most of the issues sound like algorithm matters. I also wonder whether there is any learning aspect to the software, because the measurements do improve as the session progresses.

It's not a case of algorithm matters. It lacks the fundemental measurement sources to be capable of producing accurate results.  
If you redoployed every software engineer in the world to work on the algorithm, it still won't produce accurate results.
I repeat it will *NEVER EVER* produce accurate results. 
Ye cannae break the laws of physics.

 

Avatar
racingcondor [238 posts] 3 months ago
0 likes

I'm with IanMunro. Without a direct accurate measurement of power how the hell is it going to output a good reading.

Measurement of cadence would have been easy to do accurately but it sounds like that's extrapolated as well suggesting that they're so price focussed that the additional cost for even basic real data was deemed too much. Doesn't bode well for the final product.

Avatar
DrG82 [201 posts] 3 months ago
1 like

It would be interesting to see how a Strava/Garmin estimated power output compares to the Aerofly output.  My guess is that they will be very similar.

Avatar
adamrice [8 posts] 3 months ago
5 likes

It's refreshing to read a negative review—they're scarcer than hen's teeth. So thanks for that.

Avatar
jollygoodvelo [1682 posts] 3 months ago
1 like

As above - on rollers, or maybe on track I could see how this might work.  On a road... just look at the graph.  It doesn't work.  1.5 stars for something that doesn't work, what would a product have to do to get less?

Avatar
Pub bike [253 posts] 3 months ago
0 likes
IanMunro wrote:

Air pressure in tyres is a red herring. It doesn't measure tyre pressure.

Thanks for the link.  I can see that the FBM320 can measure from 300-1100 hPa.  A tyre at 120 psi is 8273 hPa so connecting to a tyre would blow the little device up, unless they really have connected a pitot tube to the FBM320?

The device needs to determine the cadence from irregularities in the wheel motion.  Given that the wheel rotates quite slowly, the device will take many wheel rotations to converge on the correct value, so this is also not going to be very accurate.  The device would just about make a reasonable speedometer. 

A far better alternative is the PowerPod which uses wind speed and other sensors to estimate power, and broadcasts on ANT+.

 

 

Avatar
srchar [707 posts] 3 months ago
2 likes

It doesn't work, but seems to earn its 1.5 stars just because it's considerably cheaper than other options that do actually work.

I give the road.cc star system 1.5 stars.

Avatar
spen [199 posts] 3 months ago
0 likes

Strikes me that for this to work there would have to be a very good seal on the valve stem and it would be easy to fail to achieve that

Avatar
George2288 [2 posts] 1 month ago
0 likes

Arofly proposed “Arofly Device” in March, 2017. The original design was to incorporate with smartphone. 

However it was unable to reach the best performance due to limitation to GPS function from smartphone. This had led to some negative reviews for Arofly.

Our team have been spending near half year to improve this disadvantage from smartphone and further develop “Arofly A-Plus.” This has been launched in EuroBike - Germany September, 2017 and in InterBike - USA end of September, 2017 

Our team has been working really hard to check and evaluate every single review/advice/criticism before end of August and every criticism is precious for us. We take every review and advice seriously in order for our product improvement. 

*** Therefore please have re-evaluation of our updated product based on our launch in September, 2017 *** 

The following review is from a British user - Mr. Gordon Peel. Review was translated by manufacturer. Due to image right, we have Mr. Gordon’s permission to publish this review and photo. However we are still unsure about which person in the photo was Mr. Gordon Peel.

Below are two images from today's ride. We complete 80 miles, a hard day as there were a lot of hills. 

AROFLY A PLUS METER -  Review. In Gordon’s own words.                                                                                           Oct. 24 2017

The first item I fitted was the A-Plus meter which comes with a nice bracket that displays all the data in an easy to read format on the handlebars of the bike. I also attached the A-Pulse to my wrist, this is a heart monitor that sends data to the A-Plus Meter (display), so that you can view your heart rate as you ride. Finally I fitted the tiny Arofly Power Meter to the rear wheel of my bike. I wasn't sure how it would work but its a clever device that detects the tyre pressure and converts it into watts, in fact if you don't fit it correctly then the A-Plus Meter displays an on-screen warning that reads "low tyre pressure" a useful little feature.

I tested all three arofly devices over an eighty mile club ride, I especially wanted to see how the A-Plus meter could detect the wattage and cadence. From what I could see there was a definite correlation between the "effort I put in" against the Wattage displayed on the screen (A-Plus Meter). Going up hills I recorded 200/300/400 watts and yet this data seemed to be fairly accurate against the peddle resistance (effort), however, downhills the device recorded a zero as it should. Excellent I thought, but if this device works off tyre pressure then surely it would detect holes in the road? The good news is that it didn't. Some of the roads we ride on are not too good yet the A-Plus meter didn't appear to give any incorrect readings when riding over bad road surfaces. 

Having arrived back home I uploaded the data into the arofly "cloud". I was very surprise how effective the Arofly was, it provided a wealth of information about my ride. The gps had mapped my ride as you would expect but it can also be automatically uploaded from the arofly cloud directly into Strava, an essential feature in my opinion. Overall, I was surprised how well the arofly performed, its a great unit and I would imagine especially useful for Time-Trial competitors that wish to monitor data from training rides.

Regards

Gordon Peel

Avatar
George2288 [2 posts] 1 month ago
0 likes

Arofly proposed “Arofly Device” in March, 2017. The original design was to incorporate with smartphone. 

However it was unable to reach the best performance due to limitation to GPS function from smartphone. This had led to some negative reviews for Arofly.

Our team have been spending near half year to improve this disadvantage from smartphone and further develop “Arofly A-Plus.” This has been launched in EuroBike - Germany September, 2017 and in InterBike - USA end of September, 2017 

Our team has been working really hard to check and evaluate every single review/advice/criticism before end of August and every criticism is precious for us. We take every review and advice seriously in order for our product improvement. 

*** Therefore please have re-evaluation of our updated product based on our launch in September, 2017 *** 

The following review is from a British user - Mr. Gordon Peel. Review was translated by manufacturer. Due to image right, we have Mr. Gordon’s permission to publish this review and photo. However we are still unsure about which person in the photo was Mr. Gordon Peel.

Below are two images from today's ride. We complete 80 miles, a hard day as there were a lot of hills. 

AROFLY A PLUS METER -  Review. In Gordon’s own words.                                                                                           Oct. 24 2017

The first item I fitted was the A-Plus meter which comes with a nice bracket that displays all the data in an easy to read format on the handlebars of the bike. I also attached the A-Pulse to my wrist, this is a heart monitor that sends data to the A-Plus Meter (display), so that you can view your heart rate as you ride. Finally I fitted the tiny Arofly Power Meter to the rear wheel of my bike. I wasn't sure how it would work but its a clever device that detects the tyre pressure and converts it into watts, in fact if you don't fit it correctly then the A-Plus Meter displays an on-screen warning that reads "low tyre pressure" a useful little feature.

I tested all three arofly devices over an eighty mile club ride, I especially wanted to see how the A-Plus meter could detect the wattage and cadence. From what I could see there was a definite correlation between the "effort I put in" against the Wattage displayed on the screen (A-Plus Meter). Going up hills I recorded 200/300/400 watts and yet this data seemed to be fairly accurate against the peddle resistance (effort), however, downhills the device recorded a zero as it should. Excellent I thought, but if this device works off tyre pressure then surely it would detect holes in the road? The good news is that it didn't. Some of the roads we ride on are not too good yet the A-Plus meter didn't appear to give any incorrect readings when riding over bad road surfaces. 

Having arrived back home I uploaded the data into the arofly "cloud". I was very surprise how effective the Arofly was, it provided a wealth of information about my ride. The gps had mapped my ride as you would expect but it can also be automatically uploaded from the arofly cloud directly into Strava, an essential feature in my opinion. Overall, I was surprised how well the arofly performed, its a great unit and I would imagine especially useful for Time-Trial competitors that wish to monitor data from training rides.

Regards

Gordon Peel