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by Matt de Neef
September 20, 2013
There are more power meters on the market now than ever before and the iBike Newton is one such device. In this piece, Stephen Lane, a PhD candidate in training adaptation at RMIT University, reviews the iBike Newton and considers how it stacks up against some of the bigger names in cycling power meters.
I know a few people who had earlier versions of this device well before power meters became a near-necessity for competitive cyclists. I was always amazed at their positive feedback about the accuracy of the iBike but as a man of science I always questioned its validity and reliability based on its methods of calculating power. So here was my chance to put it through its paces.
The latest release in the iBike series of ‘power meters’ is aptly named after Sir Isaac Newton and his third law of physics: for every action there is an equal and opposite reaction.
After spending some time playing with this device I can say the ‘equal and opposite reaction’ does not only apply to opposing physical forces but also the psychological reaction the interface of this device can impart on the inexperienced user. But this may be a little hasty; the iBike Newton+ is actually a rather impressive device with some great features that far exceeded my expectations.
Left: The unit can display speed, power and energy expenditure on one screen. Right: Another screen shows the temperature and the time of day.
In comparison to the more familiar direct-force power meters (DFPM) such as Powertap, Quarq and SRM, the iBike calculates power using known physical and environmental variables. These include mass (rider + bike + accessories), speed of the object (rider), wind speed, rolling resistance, gradient and the drag co-efficient of the rider. Add all of these together into the correct formula and you get power which, in this case, is the amount of energy needed to overcome the forces mentioned above.
I think the biggest problem the iBike faces in gaining recognition as an equal to the more common power meters is the fact that most people don’t like what they don’t understand. In this case, unless you have a physics degree, you are likely left scratching your head in disbelief.
Installing the iBike is no major drama. It’s a matter of bolting it on and ensuring that the wind sensor is not obstructed. In saying that I could see it may present some problems on a TT rig but there are some after market adapters available to negotiate any possible problems.
Once on the bike it needs some setting up and here is where the frustration begins.
This problem stems from:
1. a lack of coherent and comprehensive instructions provided within the supplied manual
2. hard to understand screen abbreviations on the iBike itself, and
3. the range of parameters that need setting up.
I’d like to think that I’m relatively technically savvy but I had a traumatic experience trying to navigate the iBike menu and ensure everything was set up correctly. Apparently this process has been significantly improved since earlier versions but it is still a difficult task.
The use of the ‘ISAAC’ software does assist in making the process a little simpler and does work well to refine the calibration and improve its accuracy once you have a few rides worth of data. After you’ve done the initial set up, and once you become familiar with the near-over-simplified menu, the continuing use of the iBike and calibration is relatively simple.
Resuts of the calibration ride which requires an out and back 1.6km ride. Green is power, blue is the wind yellow is the amount of drafting, purple is heartrate, the brown graph shows coasting and braking, and the bottom field shows elevation.
The iBike has a relatively few display functions and features compared to what many of us are now familiar with. Yes, it measures and can display the standard parameters such as power, cadence, gradient, temperature, speed and heart rate but the integration of screens and the ability to select what you want to display is very limited.
Maybe it’s just that I am spoilt with the functionality and simplicity of the current generation of Garmin products but I just found the display options on the iBike a little prehistoric and difficult to navigate.
Furthermore, the unit doesn’t have GPS, which may be a drawback for the rider who uses such online tracking sites such as Strava or enjoys the mapping features of other products.
I think one of the biggest positive points for the iBike is that it can easily be switched from bike to bike and allows for several ‘bike profiles’ to be pre-set, allowing for an easy transition. I’d be particularly interested to see the accuracy of the device when used while mountain biking. This could be a real plus if it were accurate under these conditions.
Left: the iBike displays the strength of the wind striking the unit. Right: The unit is connected to a computer via a USB port on the back.
Is it valid? Is it reliable? These were my two biggest concerns.
Validity refers to whether the measurement is actually comparable to other power meters. If I’m riding at a known 250W does it display 250W?
Reliability is whether it accurately measures power under a range of external variables such as on a windy day, an undulating course or with repeated accelerations or sprints and does it do it accurately ride after ride?
The iBike runs ANT+ connectivity for pairing devices such as a heart rate strap, speed/cadence sensor (supplied) and a direct-force power meter. I have a Quarq on my bike so I was able to pair this up with the iBike (with some difficulty) to determine if the iBike accurately measured power over a series of rides compared to my Quarq. I have previously validated the accuracy of my Quarq using a few different methods.
Comparison of the iBike and my Quarq revealed a pretty good overall reliability. The Green line is the iBIke and the White line is my Quarq. The overall difference in average power for this 50km undulating ride was 5W. However, I believe that bigger differences may be evident when performing shorter steady intervals or intervals with repeated sharp accelerations.
This is where things started to look up. I was pleasantly surprised to see that on a few different rides the post-ride analysis using the ISAAC software showed my Quarq and the iBike were only a few watts different. The comparison graph (above) shows a pretty good overlap between the two power meters.
Although by eye it looks like a respectable comparison and proves that the iBike does have a good degree of validity, I think there are several conditions that may present problems to the accuracy of the iBike.
It appears to be reliable under steady conditions however larger variations may occur during sprinting and surging type efforts. This may be due to the nature of the measurement or the fact that subtle changes in variables such as mass (body mass + bike mass, which of course changes dependent upon bottles and typical extras), drag co-efficient (position and clothing) and rolling resistance (tyre pressure etc.) greatly influence the predicted power. If these don’t comply with the iBike’s ‘pre-set values’ an accumulation of measurement error is going to occur.
One feature that I didn’t get to experiment with is the ability to use the iBike on a stationary trainer. Within the set up you can select various types of trainer models and the iBike estimates power based upon the speed/power curve specific to your trainer.
It is a good idea but I was a little disappointed that no software update was available to include the LeMond Revolution, which is the trainer I have. Granted, you can do a ride on your trainer with the iBike and a direct-force power meter and the ISAAC software will calculate the speed/power curve for you, but again no detail is provided anywhere within the manual on how to actually do it.
The ISAAC software developed specifically for the iBike is actually quite good. Although it doesn’t run a calendar platform similar to WKO or the standard performance analysis it does allow easy exporting of files to other common analysis programs.
The ISSAC software provides the ability to analyse various aspects of cycling efficiency. Firstly, it is able to measure second-by-second changes in drag co-efficient (Cda) (if the iBike is paired to a direct-force power meter). This allows the rider to determine optimal aerodynamic position and equipment choices.
The ISAAC software can display some interesting numbers showing when you are ‘in’ vs ‘out’ of the wind. All my test rides were solo but it would be interesting to see the graph when sitting in bunch.
The second efficiency analysis specific to the iBike Newton+ and ISAAC software is what they call the ‘Power Stroke’ analysis, which utilises the iBike’s high sampling rate (16 times per second) and its ability to measure tilt. This feature allows side-to-side and front-to-back movement to be analysed in relation to the position of the cranks throughout the pedal stroke.
This then provides analysis of your pedalling efficiency represented as wasted watts and time. I won’t delve into specifics and problems I have with this function but based on the one ride I analysed apparently I pedal in squares and am like a jelly fish on the bike!
Power Stroke analysis. The needle is off the scale indicating I’m inefficient! That cant be good!
I think the iBike proved itself as a valid measure of power but I am yet to be fully convinced it is on a level playing field with the likes of Quarq, SRM and Power Tap. It was the functionality of the head unit and display that disappointed me the most. Even the price is somewhat of a stalling point.
The head unit retails for approximately $499 but by the time you add the optional heart rate strap and the Power Stroke software it jumps to $759, making it a little harder to justify when the prices of direct-force power meters have dropped considerably in recent times. But, in saying that it is both a power meter and head unit all in one.
If you are a data junkie and are willing to spend the time to figure out how to set up and use all of the functions the iBike has to offer in regards to measuring drag (which does require the concurrent use of a direct-force power meter) then you can open up some new possibilities on position and equipment testing.
This potential makes it attractive for someone like me who has a large focus on time trials and can also use the iBike as a tool to convey the importance of aerodynamic riding position during solo rides as well in group rides where drafting can significantly reduce energy expenditure.
The iBike can be used to estimate power on a trainer using a speed ‘vs’ power relationship. There is a large database of trainers to choose from.
In summary, when comparing the iBike to other power meters on the market it does lag behind in integration, simplicity and functionality. However, it also offers some great features that make it a real contender if all you want to do is collect data on your rides and then do a comprehensive analysis using the supporting software.
Would I recommend it? For certain athletes yes I would. I can see that some people would shy away from it due to its nature of measurement and lack of user-friendly interface. But, if all you want to do is look down and see power, speed and cadence then the iBike will do that.
At the other end of the spectrum the data junkie can delve into the abundance of drag, power and efficiency data the iBike collects and hopefully this will serve to improve performance.
Another down side to the iBike in this regard however is that many of the features I found to be most valuable are only achievable when you also have a direct-force power meter, which is really out of the realms for most consumers, especially those looking for a cheap entry-level power meter.
Stephen is nearing completion of a PhD in training adaptation at RMIT University and is an A-grade racer, based in Melbourne. He has previously written for CyclingTips about his experience of an eight-week altitude training program. If you’d like to read more of Stephen’s work, check out his great blog Human Performance Technologies.