The P1 pedal offers separate power measurement for the right and left leg. Installation is extremely simple and only requires an eight-millimetre hexagon socket for mounting. The pedal recognises itself in which position it is mounted, external transmitters as with the comparable Garmin system are not required - all electronics are located in the bulky pedal. This makes it easier than any other power meter to move the P1 from bike to bike. Power is supplied by one AAA battery and Powertap promises around 60 hours of battery life. Replacing the batteries with rechargeable batteries is conceivable, but is not recommended due to the lower voltage of the rechargeable battery. The manufacturer states that the pedals weigh 398 grams per pair, making them 100 to 150 grams heavier than conventional pedals.
The data transmitters in the pedals use the standard ANT+ protocol as well as Bluetooth Smart to connect to a computer and/or the associated app. The eight strain gauges per pedal for force measurement are not located on the axle but on a measuring tube between the pedal body and axle. A magnetic sensor detects the position of the pedal in 18-degree increments. The pedal should even be able to resolve force and force direction in three dimensions, but this is still a dream of the future. The test model only shows the usual performance values and the left-right balance. Justin Henkel, Technical Product Manager, explained that the ANT+ data protocol does not yet define how the additional information should be handled. "We don't want to create our own standard that is then incompatible with the rest of the world. We also want to gain experience as to which data is relevant at all," he explains. Measurement technology is obviously advancing faster than the realisation of what can be done with the data.
A Joule GPS+ device from Powertap served as the computer during the test drives. Powertap recommends checking the zero point, i.e. the calibration, at the start of every ride. This requires a few button presses on the Joule computer, which is not quite as intuitive to use as the Garmin touchscreens. The device automatically performs temperature compensation for accurate measurements in fluctuating outside temperatures. According to Powertap, two temperature sensors are installed in the pedal - one directly next to the force sensors and one on the electronics. This should ensure an exact correction of the temperature effect.
During the test rides, the temperature was fairly constant; moreover, there was no absolute scale for assessing the measured values. However, the pedal consistently displayed plausible values and worked without dropouts or delays. However, the power-saving functions currently make using the device unnecessarily complicated: The Joule computer has to be awakened from sleep mode by pressing a button after every somewhat longer stop; the pairing with the pedals then also had to be renewed several times, which is quick by pressing two buttons at the same time, but always somewhat irritating. However, the power-saving function may yet be refined. Firmware updates on the pedal are possible via Bluetooth and the app.
Mechanically, the pedal, which accepts shoe sole plates with the Look Keo standard, is inconspicuous. The release force is said to be adjustable over a wide range between 6 and 20 Newton metres and the overall height is 14 millimetres. All wear parts are replaceable. The measuring technology should withstand pedal contact on the road, for example when cornering, without complaint. According to Powertap, the crank eye is more likely to break out than the pedal axle to be damaged.
The price for a set of pedals is said to be €1,299. The manufacturer was unable to give an exact date for the sales launch, but the system is expected to come onto the market in spring 2015.
C1 crank power meter
The C1 sensor is intended for retrofitting to five-arm cranks with a 110 millimetre bolt circle (compact cranks) - Powertap therefore offers the power measurement in three versions: for the rear hub, for the pedal and for the crank. The crank sensor and a pair of chainrings, which are manufactured by FSA from a single piece (50/36, 52/36, 53/39 gradations), are available for €749. The sensor, which Powertap specifies as weighing 100 grams, is attached to the crank arms. In turn, the special chainrings (188 grams) are bolted to the sensor. Compared to an FSA chainring, this results in an additional weight of around 150 grams. The power supply is a CR2032 button cell, which should last 200 hours.
During the test ride, the C1 sensor displayed between 20 and 30 watts less than the pedals. Powertap had already announced this in advance and justified it with the unfinished software of the prototype. However, the Americans wanted to demonstrate that the system works in principle. By the time it is launched on the market, the crank measurement system should be as accurate as the other Powertap power meters.
Our impression
The simple design and foolproof installation distinguish the P1 pedal favourably from other power measurement pedals on the market. However, we found the power saving function in conjunction with the Joule GPSplus computer impractical. The new crank sensor, if it stays that way, will be the most favourable form of power measurement for both legs.
You will find an overview of the power meters available on the market here.
