Here on the Wiggle Guides site we have recently started running a series of guides on Training With Power. The series is being run in conjunction with PowerTap, one of the leaders in power measuring technology.
In this product review we consider the Powertap G3 Wheelset and the Joule GPS Headunit. The PowerTap hub-based system of measuring power is widely recognised to be one of the most affordable and best designed systems available; it is easily transferred between bikes and is well protected in the event of a crash. The Joule GPS unit is the perfect complement to the PowerTap hub; it is designed to be the ultimate power measuring unit, with a superb capability to measure intervals, drill down into data, and when linked up with the PowerAgent software it provides great analytical capabilities.
The PowerTap G3 Alloy Wheelset
PowerTap used to have a variety of hub models, now there is just the superb G3 hub that is used in all of the PowerTap wheelsets. Whether it is laced up to carbon ENVE deep sections or the PowerTap branded alloy rims on this set, this is a centerpiece to be reckoned with. The hub uses high quality ABEC bearings and power measurement is accurate to within +/- 1.5%, no other manufacturer of hub based systems has produced such a great system as is contained within the G3.
The wheelset featured in this review is the "G3 Alloy"; the hubs are therefore laced up in a three cross spoke pattern to PowerTap branded alloy rims (which are similar to Mavic Open Pros). The 32 spoke pattern on the front and rear provides a bomb-proof set of wheels that is suitable for hard training and yet light enough to satisfy most racers.
The wheelset is ANT+ compatible, which means it will transmit to computers like the Joule GPS, but also to other brands of headunits such as Garmin and the Mio 505.
With no wires and all the internal workings of the unit sealed in, there are minimal user-serviceable parts in the G3 hub. It is simply a case of putting on your chosen cassette, fitting a tyre, and you're ready to roll out and measure your power. Minimal fuss. (Note: If any parts of the G3 do need servicing, you need to send it back to the distributor to carry out the repairs, certainly don't try dismantling this hub yourself.)
The G3 hub and alloy wheelset is capable of thousands of miles of training; it is built to last, built to withstand foul weather and built to be a faultless power measurement tool. If you want an easy to fit, easily transferable power meter that can be used all year round, the PowerTap Alloy Wheelset is the way to go.
The Joule GPS Headunit
Pair a G3 wheelset with a Joule GPS headunit and you've got a package that is made to provide in-depth and highly informative power data.
The Joule GPS is a compact unit, which comes with brackets to mount it both "out front" of the handlebars or on the stem. It uses a green and grey colour contrast screen that is easy enough to read in all but the worst weather conditions, and it has three large buttons on the sides of the unit that are easy to press even with full finger gloves on.
The display on the unit is fully customizable; most easily done using the PowerAgent software, just plug the Joule into your computer and you can use the software to change the "dashboards" that you have displayed whilst training. For example, a "number one" dashboard could have Speed, Power, HR, Time, Cadence and Kilojoules. At the bottom of the screen there are then two added units, which are the "drill down" of the selected dashboard item; so for example, if you have highlighted "Speed" the drill down would show average speed and max speed. This is a great feature, it means that you are able to track the individual data well from one dashboard screen, and you can just drill down into the specific item that is of interest at any one time just by flicking through the units with the buttons on each side of the Joule.
The Joule really comes into its own when you start using it for interval training. Hit the big interval button on the front of the Joule and you will stop your last interval and start your next one. This is a great feature for power training; as is highlighted in the Power Training Guides, the best sessions for a power meter are doing intervals at a certain power level, therefore being able to record the data for individual intervals is vital.
Plug the Joule into the free PowerAgent Software and you have an infinite amount of analysis that you can carry out. PowerAgent will dissect every training file to provide graphs, summaries, averages and totals for every figure you could think of; from power and output balance, to elevation and speed. Whilst uploading data to the PowerAgent software you also have the option to automatically upload to Strava, TrainingPeaks and other sharing sites; providing further capabilities to drill down into your data.
The unit starts/stops automatically with movement, or when it detects a heart beat from a heart rate monitor. There is no manual means to start and stop recording. This may frustrate some riders, however you have to remember that the key to power training is the intervals that you do out on the road. If your computer inadvertently records you walking up your drive at a low speed that "damages" your average, it is not this average speed or power you should be concerned about, it's the one during your intervals that you do mid-ride that matter!
Battery life is very respectable; lasting for long days of 6 hours in the saddle without running out. The unit then charges up via the USB port as soon as you plug it in to download your data. The Joule also has a mapping facility which enables you to trace the route you have taken, and provide a directional arrow to show you the way back to a "waypoint"; this feature is a great "get me home I'm lost" addition, and is sure to come in useful when out training in a "foreign" location.
Overall, the PowerTap Joule GPS is a great piece of kit, and a super little computer for those that are looking to specialise in power training.