First things first, what does a power-meter actually do
and why do you need one? Traditionally cycling performance has been measured by
using a basic sensor fitted to the bike which tracks and monitors speed,
distance and, more recently, cadence. Within those features we also have
average speeds, max speeds attained, etc. Whilst this information is good and
for most people who just want to keep a general record of miles ridden and
average speeds probably all that is necessary, however the data and feedback
does not take into account ride conditions such as headwind, tailwind, altitude
or gradients. More importantly there is no measure of effort from you, the
Lots of riders nowadays use some form of cardiac
feedback, usually in the form of a band with a sensor worn about the chest and,
though this data is useful, it still has large gaps and omissions plus it is
wildly inaccurate at times. Again, outside factors of terrain and climate, altitude,
whether you had a late night or two shots of espresso before you started all
have effects on your base line. There is also a significant lag between
pedaling output and your hearts increased beat rate.
So this is where a power meter takes over. It
really is the only accurate way to gauge and compare performance. Power-meters
measure power output in wattage and, more importantly, remove all the variables
from the data. As an example; you completed a ride last week in fair weather
and kept up a steady output of 285 watts for two, twenty minute training intervals.
Today you did the same ride, this time in driving rain and a headwind but still
completed two, twenty minute intervals, your distance covered was much shorter
but your power output was 288 watts. You did better, but your ordinary computer
would show that as a bad day. With the power meter this is accurate usable
data, no need to discount the day or make notes to allow for bad weather. Watts
are an accurate measurement of your performance regardless of all the changing
forces acting against you. The end result is a phenomenal training tool and
record of improvement.
During racing and endurance events it is a
great source of feedback for maintaining calorie intake to match output and
also keeping a comfortable pace for a long endurance event.
So, now that we have covered
what a power meter can do for you we shall take a quick look at your main
choices. The benchmark device is
probably the SRM range of crank mounted power meters. Very reliable, accurate
and the company has been producing meters for many years. Sadly though, what
limits their popularity is the price. While any of these devices are not cheap,
setting up a bike with an SRM unit is going to run around 3 grand. Ouch.
Next in the line-up is Ergomo,
these guys produce a solid, bottom bracket device which you can install with a
crank-set of your choice. Accurate and the company produce the usual range of
data analysis software. Ergomo is cheaper than the SRM meters but still a
little more expensive for a full system setup than the third choice.
Power-Tap from CycleOps is about the cheapest
option for a reliable power meter system and, for that reason, it is this
system I shall concentrate on here. Still not cheap but they do have an option below
a $1000 which is considerably less than the SRM. Even the top of the line G3
ceramic is less than the next player in the market and for that reason alone
Power tap has become a very popular choice.
I shall start at the top with
the G3 ceramic. This hub is the world’s lightest power meter and the complete
hubs weigh in at a mere 315g. Next we have the standard G3, basically the same
hub but without the ceramic bearings. The weight is still excellent at 325g and
you can always upgrade to a ceramic bearing at a later date if you feel the
need. The G3 series hubs are a complete makeover from the original power tap
hubs. They have a significantly reworked body and allow for much easier servicing.
One of the main differences and to my mind the most important one is the
increased gap between the flanges. This dimension is very important and affects
greatly the final strength of the wheel. The G3 series hubs increase the gap by
5.6mm over the original models and this makes it possible to build a very stiff
and strong wheel, the dimensions are much the same as any road race hub in fact.
The original design is still available;
it is called the Power-Tap Pro. With a sticker price of less than 900 a hub it
is by far the cheapest meter option out there. Each year it gets a basic
makeover to keep the internals up to date but shape and external dimensions
have changed little. The pro is a fine piece of equipment and has accuracy the
same as the G series, all the hubs have great accuracy, to within +/- 1.5%, and
the company produces a great range of analytical software, it is quite a bit
heavier than the G3s but it is also a lot cheaper. Over the years we have built
a lot of them up and I always recommend getting one with a higher spoke count.
With the closeness of the flanges on this hub we need to get as much strength
as we can from the spoke number. You are not going to be making massive weight
savings opting for the 24 spoke, not when the hub itself is 450g, so do
yourself a favor and opt for the 32. With a 2x pattern and maybe an offset rim
or a deep V at least, it can be built up quite strong and stiff.
When used for training purposes
and accurate performance recording the standard Power-Tap Pro is a fine choice
however, if like many you are looking for a wheel to race with I would suggest
opting for the G3 series. These hubs are much the same as any of the many race
hubs that we use and with the extra flange width I can build a super race wheel
that gives you feedback as well.
A final thought on some other
options. Recently there have been some forays into the power meter market by a
few well known players. Over the past few months I have read some interesting
press releases with regard to pedal devices. On the face of it a pedal option
sounds a good idea, easy to transfer from bike to bike for one. But some of the
price points that I have seen are ludicrous and I would like to see them in
action first with some good field testing and data collection behind them. Some
of the accuracy reports I have seen are a little disappointing, but it is early
days. For the moment I suggest the Power-Tap , for best accuracy and bang for