Ingezonden

The Look KeO Power pedal, developed in conjunction with
Polar, is the first pedal power meter to make it to market. After testing a set
for a few months, we think they pass muster for a first-generation power meter. We’d like to see some improvements further down the track, though, and at £1,500 for the
pedals alone, they’re not cheap.

The system is relatively simple – eight strain gauges located in the axle
measure pedalling force, while a reed switch in the pedal body measures cadence.
These recordings are then sent to a Polar computer using Bluetooth Low Energy (BLE) via a transmitter
that connects to the inner side of the crank arms. The computer translates the
data into power, even breaking it down into left/right leg contributions.

Our pedals weighed 344g, which, combined with 36g for the sensors and 40g for
the computer, makes for one seriously light power meter. 

The installation

The good thing about the Look KeO Power pedals is that you can install them
yourself. Be prepared to spend some time doing so, though, as it’s not as
simple as screwing on a set of pedals. The pedals come with washers and lock
nuts as well as an alignment tool. There’s a notch on the end of the axle that
you need to align so that it’s pointing forwards when the crank arm is in the
12 o’clock position. Get this wrong and your power measurement will be out, as
we found on more than one occasion. 

In practice, we found that the 8mm Allen key
alignment tool didn’t really help, as there was too much freeplay between it and
the drive hole. Also, the lock nut had to be really tight in
order to prevent the axle coming loose during the ride, messing up
the alignment of the transmitter. Once the pedals are correctly aligned, the
transmitters just push on and are secured with zip ties. 

The left transmitter acts as the master in the whole setup, and can be switched
on and off via a small button. When you first use the Look KeO Powers you need to set your
crank length. You have a choice between 170mm, 172.5mm, 175mm and 177.5mm.
Zeroing happens automatically when you turn the transmitters on, although it’s
impossible to check against any sort of baseline value. 

Like most power meters, the Look KeO Power pedals will
experience some drift in readings due to temperature changes, although Look say
that it’s not large. If you’re concerned then you can re-zero after 20-30 minutes by switching them off and on again. This means you have
to get off the bike, though. We found we got better results by not zeroing them after we’d
started (see below).

Sensors sit on the inside of the crank arm

The measurement

The pedals measure power and cadence, which means you’ll need a speed sensor
and heart rate monitor if you want to know speed, distance, time and heart rate. The
Polar computers will measure altitude too – we used a CS600X for this test, but
the KeO Power system will also work with a CS500 and CS600.

We were interested in power, primarily, and after we worked our way
through all the teething problems mentioned above, we were mostly happy with
the numbers we were getting. We used a PowerTap SL+ hub-based power meter to do
comparative testing both indoors and on the road. The PowerTap had been checked
against a Computrainer in ergo mode, as well as a static weights test
to ensure calculated torque was the same as measured torque.

Using a stationary trainer indoors, in controlled conditions, riding at
different power levels, we found the wattages we were getting from the Look KeO
Power pedals matched our PowerTap to within 1-2 watts. 

Outdoors, we found a
similar correlation but only if we relied on just one pre-ride zero and
didn’t stop to zero mid-ride. If we did the latter, we saw our Look KeO Power
numbers shoot up by roughly 10 precent compared to our PowerTap. 

We verified that it wasn’t our
PowerTap reading low by comparing power and speed over laps of a known circuit.
All things being roughly equal, it shouldn’t be possible to go significantly
slower while putting out more power than you did on the previous lap. We’re not exactly sure why this was happening, but it’s something to
be aware of if you’re considering the system.

Polar’s CS600X computer

The software

Data analysis has to be done via Polar’s ProTrainer 5 software, which gives you a lot of data and analysis options but isn’t as easy to use as the
market-leading WKO+ 3.0. We’re told that ProTrainer 5 is due a major upgrade
this year. 

The same goes for Polar’s computers, which have some nice functions
but lack the fields we’re used to working with on the Garmin Edge and CycleOps
Joule
head units. Unfortunately, the Look KeO Power system isn’t ANT+
compatible, which means it can’t talk to the latter head units. In principle, it can communicate with other BLE devices, such as the Apple iPhone 4S,
without as big a battery drain as ANT+.

The verdict

Look and Polar have brought an impressive product to the power meter market,
the main advantage being the light weight and the transferability between
different bikes. 

We’d like to see an easier method of ensuring that the transmitters
are aligned correctly, a better way of keeping the zero offset in check during
a ride, and the price come down. This would mean the Look KeO Power system could be truly competitive with existing
power meters, as well as the Garmin Vector when it eventually surfaces.

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