Where To Fit A Power Meter On Your Bike | GCN Tech Does Science

Where To Fit A Power Meter On Your Bike | GCN Tech Does Science


(dramatic thuds) (upbeat music) – Training with power has become one of the most talked about ways of both improving performance and
fitness in recent years. Gone are the days of being out, slogging yourself for hours on end, and well, just hoping for
the best in terms of fitness. However, what’s really
important is actually the consistency of data in which you’re getting back from a power meter. As much as we all like to think we’ve got a really high number,
if it’s wildly inaccurate, well, it’s not really
gonna help you is it? So, thanks to our friends at PowerTap, we’ve got a few different
ways in which we can measure power whilst you are riding along. So, come on, let’s go
and take a look at it. Now, where exactly are we gonna measure all this power from, then? Well, we’ve got five different devices that we are gonna connect to and see just how accurate that data can be. (upbeat music) First up is the PowerTap Rear Hub. Now, the PowerTap hub system has been around for about 20 years now. Obviously during that time,
it’s undergone some refinements and developments, and
it’s gone from what was initially a wired unit,
to what we now have, a wire-free unit, which is good
news for everyone out there who doesn’t like extra
wires on their bikes. So, this is the G3 Hub,
and as you can see, it’s an oversized hub-shell unit, which all of the strain
gauges and electronics are actually housed
within, and then the torque you’re putting through the
rear wheel is transferred, that data into power,
sent on to the head unit. Now it is a very easy installation process if you buy a pre-built wheel. It’s simply a case of
putting it in the bike, pairing it up to your head
unit, and away you go. There’s also no need
to send the wheel back to a service center in the
case of a battery change. It is easily done by yourself at home, so simply unscrewing the endcap, and then replacing that
battery, nice and easy. Now I have already touched on it, but it is a really great
transportable piece of power measurement
equipment if you’ve got a few different bikes, so you
can simply remove the wheel and then put it into another bike and have power measured from that too. Now many experts like that actually claim that the hub-based system
is one of the most accurate ways to measure power out there, because, essentially,
you’ve got less variables that are going on, so there’s less things such as a chainring moving,
and that kind of thing. Now PowerTap, themselves,
have actually told me that basically the hub
system can sometimes underread that total max power,
the reason for that being, is obviously with the
drivetrain components, you do have a little bit of loss off that raw power
being sent through that. However, it is accurate to
plus or minus 1.5% accuracy, so you’re pretty much on
the money there, anyway. (upbeat music) Now, secondly, and this is
a relatively newcomer really to the power meter game, is pedals. So the PowerTap P1 Pedals, as you can see, there is the battery which is
housed inside of the unit here as well as the strain gauges, so basically it’s all tucked away nicely
underneath the pedal. Initially, they do look like
they have a little bit of bulk, but, hey, when you’re riding along, you can’t actually see
that anyway, can you? So it doesn’t really matter. And what do I really
like about these pedals? Well firstly, they’re highly
portable, aren’t they? So if you’ve got more than one bike, you can easily switch them
around from bike to bike, certainly easier than that
of a chainset, for instance. And say, if you had a hub
built onto a training wheel, you wouldn’t necessarily want to use that in a race situation, would you? And then we’ve got AAA batteries, too. So, if you were in the
unfortunate situation, and you forgot to actually
check how much power was inside of your
battery, and you ran out, you could easily find a AAA battery from virtually any shop on any
street in the world, I guess. Now, data, again is transmitted
for ANT+ or Bluetooth. And then in this case, we’ve
actually got dual-sided, so it’s a left and
right power measurement, so one pedal talks to the other, and then that pedal send the
information to the head unit. Now, there is also the option to run it as a single-sided unit, so you buy a pair of almost identical pedals,
well they are other than the right-hand side pedal doesn’t have any of the electronics inside of it. Instead, it’s the left pedal
which transmits the data to the head unit, and then
to find out your total power, essentially it doubles that
because most people out there actually have an even split
50/50 or there, or thereabouts. Now, finally, let’s talk about the actual cleat system that fits in here. Our first look, they do look extremely similar to that of a Look KEO pedal. However, they are slightly more oversized, so if you were to use a Look KEO in there, it’s not going to give you
that accurate power reading as well as potentially
being dangerous as you could unclip, so it’s worth
sticking actually with those PowerTap-specific cleats, which do come with six degrees float or fixed. And just like the hub system, it’s accurate to plus or minus 1.5%. (upbeat music) Now next up is the PowerTap
C1 Chainring systems. Now there’s no actual competition on the market for them
as far as I’m aware. So how do they work? So out of the box, they come as a pair of FSA chainrings which are
mounted onto what’s essentially a secondary spider, which
houses some of the magic of a power meter inside of it. And then, it’s also got the sender unit, so that’s the transmit via
ANT+ or Bluetooth again, as well as the battery which is fitted onto the chainring, too. That then fits onto compatible chainsets, so in this case, it’s 110 BCD,
and that’s a five-arm crank. And then, the actual
power itself is measured from the outside of the inner-chainring, which is really super
interesting, for me anyway. So interestingly, despite
the data collector actually being on the
right-hand side of the bike, it does actually measure
left/right balance. How’s that done though? Well, it’s all due to
the actual positioning of the chainring, so if you were to put it in a different position on the spider, it’s not gonna give you accurate readings. Now, it is actually done on
an assumption, basically, of your pedal stroke, so
hence the reason for it having to be in the right
place on the spider. (upbeat music) Heart rate. That’s right, I said heart rate. Nothing to do with power, although it is, because this is actually an
entry into the power meter game, because using a clever algorithm, you connect this heart-rate
strap to your head unit or your smartphone, for instance, and it gives you an estimation, basically, of your power output. Now, naturally, this is
no where near the cost of anything else on the
bike that we’re measuring power from, but it is a great
entry-level starting point for you to be able to train with power. And the great news out there for people who aren’t particularly technically-minded when it comes to changing
bits around on a bike is, well, it doesn’t even have
to go on a bike, does it? It just goes on yourself,
so you can use it across all of your different bikes. (upbeat music) Finally, we’ve got a
crank-based power meter here. This one from Stages, and as you can see, the actual electronic gubbins
of it are actually here on the inside of the left-hand crank. So, we’ve got the string gauges, and also a user-changeable
battery there, too. It doesn’t add much weight at all to the actual original
crank, and they do actually come in quite a few
different varieties, too, so matching up with most
chainsets out there on the market. And just like all the other power meters, or most of them out
there, you’ve got yourself a user-changeable battery, as well as connecting via ANT+ or Bluetooth. So we’ve gone through the
five different power meters, but how, actually, are we gonna measure and record the data being captured? Well, this is where this comes in handy, mission control, or something like that. Anyway, I’ve got five Wahoo
ELEMNT BOLT GPS devices. Each one is paired up to a power meter. I’m now gonna go out
for a pedal on the bike, and when I get back, I’m
gonna be able to analyze and see just how consistent
each power meter really is. (active music) So let’s look, then, at the
all-important consistency of the data that was being recorded. Now this is a little
bit of GCN Does Science, and I’m using DC Rainmaker’s
analyzer software here, so you can see there is
different lines on the graph, and that does represent each
power meter that we’ve used. On the far left-hand side of the screen, we’ve got the power measured in watts, and that’s versus time
along here at the bottom. Now if I was to hover my cursor, basically it lets me know what power meter is measuring what power up
here in the right-hand side. So we can actually see up-to-the-second information, which is pretty cool. Now you can see that
there is one power meter which is not tracking quite as high as the rest, but more on that later on. But the good news is, that by and large, everything is tracking
in the same trajectory, as you can see, so the lines do actually follow the
same, which is good news. Now first of all, let’s actually look at the uppermost three lines on our graph. So, as you can see, they
are tracking each other very closely, and on occasion, in fact, the pink and green ones are, in fact, shadowing one another,
giving very similar readings. So what are they? Well, the green one,
that’s the PowerTap G3, so that’s the hub-based unit, and then the pink one is the PowerTap C1, and that is very, very interesting indeed. They do track, like I say, and shadow one another at those peaks and troughs. Now as for the orange line, well that’s the PowerTap P1 Pedals. And you can see, again, it
does follow exactly the same lines as the other two power
meters I’ve just mentioned. There’s a slight dip
here, just after 11:39, and I know exactly what that was. That’s where I encountered some traffic, and I actually had to
unclip one of my pedals, because I had to stop
at some traffic lights momentarily before getting going again, so nothing to worry about there. Now those previous three power meters I’ve just spoke about all actually measure a left and right power
measurement, giving the total. Whereas the Stages,
which is the blue line, just measures the left,
and then doubles it up and gives you your total power reading. Now I know, from a serious
crash I had a few years ago, that my left leg is considerably
weaker than my right, so that could be why it’s not
giving such high readings. But essentially, it is still tracking on the same lines, so
we’re all good there. Now for the black line. So this represents the PowerCal, which is the heart-rate based power meter. Now instantly you can
see it does lag slightly behind the peaks and troughs
of the other power meters, the reason for that being,
when you are putting in any momentarily anaerobic effort, obviously your heart rate
doesn’t instantaneously react to that, so that does explain it. Plus, it does also follow,
generally, the same lines, so that is good news after all. Now, at this point, I must actually say that PowerTap, themselves,
say the PowerCal is not the be-all and end-all solution
to training with power, it’s more of an introduction to it. Also, my maximum heart
rate is actually quite low for my age, believe it
or not, so it’s 174. It always has been, ever
since I started training with heart rate back in
1995, believe it or not. So that could be, possibly,
why my power reading isn’t as high as the
rest, so that’s obviously using the formula of 220 minus your age being your maximum heart rate. But, the good news is,
like I said earlier, it does track, generally,
in the same trajectory as the other power meters out there. So what’s important
here is that, generally, all of the power meters
do track with one another, so there’s no crazy dips
or spikes in the graph, which is basically gonna give you misleading results in the long-term. Now, as for is there a
best place to actually put a power meter on the bike? Well, there’s a few variables here. So, your budget as well
as compatibility issues. So if you’ve got just one bike, maybe the chainring solution is for you, because that’s very much a
fix-and-forget type situation, cause you don’t want to be
swapping them from bike to bike. A couple of bikes, maybe
you’re looking at the pedals to move around, and the
same goes for a wheel too. Just think about the future if you’re gonna buy any more bits of equipment. So there we are. I’m sure you’ll agree some pretty interesting results, there. But what I really want to know
is, do you train with power, and if so, what method do you use? Let me know down there
in the comments below. Remember, as well, to
like and share this video with a friend, especially if you’ve got a friend who trains in the Dark Ages, and just smashes himself for hours on end. Anyway, do remember as
well, check out the GCN Shop at shop.globalcyclingnetwork.com. And also, check out another video on training with power, click just down here.