Power Meter Guide
According to no less and expert than Joe Friel, “A power meter is the best training tool you can put on your bike … a power meter can take you from the middle of the pack to the podium in one season,” he writes in his new book, The Power Meter Handbook.
While that statement doesn’t accurately reflect all the hard work that goes into that dramatic a performance increase, it certainly illustrates how useful a tool a power meter can be. There are a number of different types of power meters available these days, which can be divided into three different types: hub models (PowerTap), crankset models (SRM, Quarq and Power2Max) and pedal models (Look Keo Power). We did some long-term tests on all of these from May through October of last year, putting them through the rigours of training and racing.
Regardless of where the power meter is set up, the principle is pretty much the same – power meters utilize strain gauges to measure the amount of power you are using to push on your pedals. In theory the number of strain gauges utilized will provide more accurate results. Unless you need concrete numbers in order to evaluate the amount of power generated, though, accuracy won’t be as important to you as consistency. In other words, what’s of greatest concern is whether or not the power meter remains accurate from day to day – in other words – when you’re pushing 150 watts on Wednesday it reads the same as when you’re doing the same amount of work on Saturday.
Considering the amount of money you’re spending on a power meter, it should come as no surprise that all the units we reviewed are very reliable.
SRM Shimano Dura Ace 7900
The original crankset based power meter, SRM is considered the industry standard when it comes to power meters and is utilized by many pro cycling teams and pro triathletes. The SRM comes with its own head unit, or controller, making it unique amongst the crankset and hub units we reviewed. The SRM uses eight strain gauges, which ensures a high level of accuracy.
These German-made crankset based meters are considerably less expensive than the other crankset models we reviewed. These units use four sealed strain gauges to measure power. You don’t need a cadence sensor with this unit – that’s done internally, which is a nice touch.
There are 60 different variations of crank units available with the Power2Max, so you shouldn’t have any problems getting one to fit your bike properly.
Quarq SRM S975
Jim Meyer developed the Quarq power meter when he was training full-time as a triathlete and couldn’t afford to buy himself a power meter, so he used his degree from MIT to build his own. His company is now owned by SRAM. The Quarp power meter utilizes 10 strain gauges to measure your power output.
Until a few years ago, your only options in the world of power measurement was the SRM crankset power meter or the more affordable hub-based PowerTap models. Over the years these power-measuring hubs have become considerably lighter – the G3 hub we reviewed came set up on a lightweight alloy wheelset that offered a great ride and were an outstanding training wheel. The G3 hub has eight strain gauges to measure the amount of power you’re putting into each pedal stroke.
$2,300 (Pedals and Polar CS600X $2,650)
Look Keo Pwer Pedals
Relatively new to the market, the Look system measures power output through eight strain gauges in each pedal. Look has teamed up with Polar in the development of these pedals, so they are compatible with Polar’s CS500, CS600 and CS600X computers. (Since they are some of our favourite bicycle computers, this is a very good thing!) The idea is to be able to move your pedals easily from one bike to another, but as you’ll see, that wasn’t quite as easy as we’d hoped.
Ease of set up: Hardware
We had a variety of local bike stores install the crankset power meters onto the various bikes we used for review. The SRM we reviewed came specifically calibrated and set up for Shimano Dura Ace, the Quarq was set up for SRAM Red in a true triathlon-type set up (56 chainring), while the Power2Max came with Rotor Cranks. Since a lot of the work had been done by the manufacturers before the units left the factory, for the most part the set up for all of these was relatively easy. Our Power2Max reviewer wanted to utilize a different front crank, which wasn’t a problem since the Power2Max automatically recalibrates every time you stop pedaling.
The CycleOps PowerTap unit was by far the easiest to set up – all you have to do is put the wheel on your bike and off you’re ready to go.
By far the trickiest set up was the Look Keo Power Pedals. The set up was very finicky, requiring a lot of precision. It’s not as easy as just putting on the pedals – you need to attach the “pod” to each pedal and make sure it’s oriented correctly in order to make them work. Once you do, though, the system quickly connected to the Polar CS600.
Ease of set up: Computer and Software
Since the SRM and the Look Keo Pedals come with their own computers, it was easy to get the head unit mounted on the handlebars and quickly get readings.
We set up the Quarq, PowerTap and Power2Max with two different types of Timex computers (the Cycle Trainer and the Global Trainer watch) along with the CycleOps Joule. Both the Timex units required a software upgrade, but once we did that upgrade the Ant+ compatible meters and computers quickly started communicating with each other. As one would expect, the Joule unit worked immediately with the CycleOps G3 hub.
Once set up, all the units were extremely reliable and provided consistent data. We did have some issues with the magnet of the SRM unit, which got moved around during travel a few times and had to be adjusted. We never had to replace any batteries during our tests – the SRM unit’s battery life is advertised at 1,400 hours of use, so it comes as no surprise that we didn’t need to replace that. (As much as we’d have loved to have worn it out!) The company suggests that you send the unit back once a year to replace the battery and recalibrate the unit, which can be done in just a matter of days.
Both the Power2Max and Quarq units have an easily replaceable battery so you don’t have to send the unit away. The CycleOps hub batteries are also easily replaced by using the included hub cap wrench. The Polar Keo batteries (there is one in each of the pods that attach to the pedals) can also be replaced by simply twisting off the cap.
We found all the meters to be quite consistent. While our tests with a CompuTrainer saw differences of almost 5 watts between the various meters for efforts over 200 watts, the differences were consistent from test to test for each unit. We’re not sure how much of those changes are based on calibration versus accuracy of the units, but, as mentioned earlier, consistency was more of an issue for our review than accuracy.
Of the crankset meters, we did notice some variation within the Power2Max unit based on temperature. That wasn’t an issue at all in the summer, when most of our rides were done in the heat, but in the fall when we were on rides that saw a huge temperature change, the power numbers did change a bit after we calibrated the unit. (Which, as we mentioned earlier, is very easy to do – it auto-calibrates every time you stop pedaling.) A software update announced this fall will likely alleviate a lot of those problems.
Deciding which of these units is best for you will be a tough call. Of the crankset meters, the Power2Max is certainly worth a serious look because of the price and ease of use. That said, it’s impossible to go wrong with the Quarq or SRM models, which have been around for longer and are the units your local bike store are more likely to stock.
The old knock on the PowerTap hubs were that they were heavy and that you basically needed two if you were going to have one wheel for training and another for racing. The weight option is basically a moot point now thanks to the lightweight G3 hub. There are a couple of options if you want to avoid getting two hubs, too. You can pick a race wheel that is a bit more durable so you can do your training on it, or you can turn your training wheel into a disc for races by using a wheel cover. The PowerTap is by far the easiest of all of the power meters to move between different bikes, since all you need to do is remove an dreplace the wheel.
While the Look Keo Power Pedal was the trickiest of all the units to set up, it is probably the lightest of all of the options and, if you like Polar computers and are looking for the most accurate left and right leg power data, is your best option.
$180, (with Heart Rate Monitor $230)
Specifically designed for cyclists who train with power, the Ant+ compatible Joule is a small, sleek and simple bike computer that offers a completely customizable dashboard. There are 18 different metrics you can choose from including power, heart rate, speed, distance and altitude. It connects easily to compatible power meters (in our case all but the Look Keo Power) and, after your ride, it’s very easy to download all your information to your computer through the included USB cable.
$295, (with Heart Rate Monitor $375)
Timex Ironman Global Trainer
$275 with Heart Rate Monitor
Timex Cycle Trainer 2.0
Using GPS technology, the Timex Cycle Trainer and the Global Trainer both provide power information while you’re cycling. Both can be set up to measure speed, distance, power, cadence, but the Cycle Trainer add a bit more to the mix including temperature and a barometric sensor for live elevation and grade data. The Global Trainer features a large face that can show up to four panes of information at a time. Both come with a heart rate monitor strap and are compatible with Ant+ wireless sensors. Both come with an included cable and software so you can easily download your data from your computer. Timex also offers a free online log through TrainingPeaks.
Polar CS600S (GPS version with the G5 included)
For this review we used the tinyCS600 specifically with the Look Keo Power Pedals. Rather than utilize the compatible speed sensor, we tried out the GPS unit that’s an option with this model, which provided speed and distance information. In addition to temperature, grade and elevation, the CS600 also measures power output from the Look Keo pedals. Since power is measured at each pedal, this is the only system that offers true left and right power data. (Other systems do provide that information, but it’s extrapolated.) Data is transferred through an infrared connection to your computer.