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Gear Reviews Power Meters

Stages power meter review

Power meters are currently the buzz word in cycling. They are also a key to a vastly different form of training. Like GPS several years ago, most costs a lot. Here I look at one of the lower cost offerings from Stages. – Updated 31/05/15

STAGES Power meter review

I suppose the big question is always going to be “Why do I need a power meter?”

The answer to that largely depends on how you are and why you are cycling. Assuming you are not a professional athlete nor doing any active competition of the arguments for buying a power meter are actually the same as why you need a GPS cycling computer. You don’t. But the extra data helps you know more about how you are riding and your own performance, which then translates into fitness.

I’m currently not competing after my injury, heck I’m certainly not racing. So why did I buy a power meter?

DATA.

Data is the all important factor for fitness, let alone training. The quality of that data is actually more important than the data itself.

For example:

– You have one data file from your last ride. But only the speed data has been recorded. Your average speed is 33km/hr. Excellent. But that ins all it shows. What it doesn’t tell you is that entire ride was on a downhill. A power meter would tell you the actual force YOU were putting through the bike. The speed data does not allow you to discount the other factors such as the speed gained from gravity going down hill, your positioning, the wind tail wind you are riding with

Example 2

– You go on a routine spin after work. Your normal route. When you return  it turns out you’ve completed your spin at the same as your previous PB for that route. Even though it felt a little easier to you, it doesn’t look like you’ve improved when you look at the GPS data. You have completed it in exactly the time, and same overall average speed as well, so no benefit there either. You don’t feel particularly as though this is an achievement, even though the ride felt “better” to you

However with the power meter, you look at your normalised power over the ride, and realise that although the time and the speed are the same. You have had a lower cadence, and increased power over all. Your legs, with training, have become more efficient. What this really says about that ride is you didn’t try hard enough!

Ultimately a power meter allows you to look beyond the speed of your bike, as this a result that is affected by many variables outside of your control. E.g. A strong head wind.

The power meter allows you to train in any situation effectively.

Example 3

Staying with the wind idea. Yesterday you went out and slogged into the head wind, and felt really rather disappointed. It sapped all of your speed and strength. Basically you felt naff.

Next day you install a power meter. Getting back into the and wind, you let the fierce Nor-Easterly take chunks out of your speed, but that doesn’t matter, as you are aiming for a set power output, as measured from the power meter, showing on your head unit.

You finish the ride. Your speed was NAFF! BUT the power meter records good adherence to the power target you set out. Even if you speed has lots of variables placed on it, e.g. the blustery day, the power meter shows the WORK your legs are doing regardless, and gives you an isolated training metric

Heart Rate power

Strava has the ability to give you estimated power outputs. This is based upon your heart rate, and works in the same way as the PowerTap Heart rate monitor. The Strava approach is a valid way of starting training, but as can be seen from the below graph, the heart rate tends to lag behind the actual power. So its useful for an overview of your ride, but doesn’t really help in terms of moment to moment training with ride data

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Notice the heart rate (red) lag compared to the power (orange)

Stages Cycling

Stages caused a minor upset the cycling world when it first launched its power meter. Particularly as it was the first power meter to breach under $800 mark in 2013. It alooks only measures power from the tT leg. Initially opinions ranges from “Insanity” to “Interesting, let’s see how it compares”

Given the success of Stages, and the proliferation of other LEFT side only power meters, it’s safe to say that results have confirmed sufficient accuracy for cycling use. If it’s accurate enough for the likes of Team Sky, that’s a good suggetion of reliable data.

The important thing about leg discrepancies, is unless you are recovering from an injury on a leg, its likely the discrepancy will always be there. So as long as that discrepancy is constant – some people are aware of an early fatigue in one leg – from one ride to the next, the data that Stages provides will still be consistent as well, and thats the important part. Consistency.

The power meter itself is a little black pod, containing the strain gauges, which attached to the inside of “approved” LEFT cranks.

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Little Black pod

Stages buy in various cranks, of series and length, from the different manufacturers and apply the pod themselves, before selling the complete crank on to the end user. They need the manufacturer to approve the use of Stages, and their bonding approach as to not affect the cranks warranty. This is the only reason they dont offer on every available crank.

Fear not from a weight perspective either, the addition of the pod adds only a slim 20g to the side of the crank. Making the Stages one of the lightest power meters out there. In addition, as the user merely needs to change the crank, it is currently one of the easiest power meters to install until the PowerTap pedals are released.

Currently Stages is not compatible with carbon cranks, mainly as carbon, due to the weave, doesn’t deform, and return in a reliable fashion, something needed for strain gauges currently, although this is being investigated by their R&D dept.


Features round up

  • – Weight 20g
  • – LEFT power only (doubled for total power output)
  • – Approved cranks only
  • – No carbon cranks yet
  • – CR2032 battery lasts ~300 hours
  • – Transmits on Bluetooth Smart and ANT+
  • – Measures cadence as well as power
  • – Includes internal thermometer to allow auto temperature zeroing.
  • – IPX7 waterproofing. So good for 30mins at a 1meter depth of water.

Stages in Use

I’ve been using the Stages Power meter, as part of an Ultegra 6800 crank for a little over three months now, here are my initial thoughts:

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Spot the pod

The Stages crank is supremely simple to install. I’m not a bike mech by any stretch of the imagination, but this was a doddle!

The pod protrudes towards the frame, but only slightly. There are few bikes I would imagine are incompatible, but Stages has a guide on their site, how t check your frame for clearance, you want piece of mind before you buy

One thing I am very found of with the Stages power meter is how it disappears. Without the company logo on the bottom of the crank, to the casual observer, it looks like a completely stock chainset.

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Stages logo is the only identifier

Once the crank has been installed, thats it. The power meter goes to sleep until it is spun round. As with any power meter, its always important to preform a calibration before every ride. Calibration is done with the pedals attached, rider unclipped, crank at the 6 O’clock position. The calibration is normally an option on your cycling head unit, and i’ve found very unobtrusive, taking about 4 seconds on average.

Zeroing

Some power meters need to be manually zeroed depending on changes in the temperature. You will see their readings begin to trend off as you ascend large climbs – not a problem in Warwick, but still – this is due to the temperature affecting the strain gauge. The  Stages power meter includes a thermometer, so it can self zero during a ride, so the strain gauge  that comprises the power meter is unaffected by changes in temperature.

Connectivity

The inclusion of Bluetooth smart is an excellent touch, both as it means it works with TrainerRoad right out of the box on my Mac, but also allows for easy (ish) updates to the power meter firmware from any Bluetooth smart phone.

I think  should probably address that (ish) now. The ONLY problem I have had with the Stages has been Bluetooth Connectivity. Which took a bit of figuring out. With Ant+ I can have it connected to as many devices as I want. With Bluetooth, I can have it only connected to ONE device in total, at all.

What I mean was I spent quite a while trying to pair with my phone, Mac, anything with Bluetooth. What I didn’t understand was that if this Stages has a connection – doesn’t have to be active – to ANYTHING else, even over ANT+ it won’t connect over Bluetooth. I only found this by going round the room and switching off ALL of my other gadgets that connect to their Stages.

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Spinning and going nowhere

This was a little surprising and annoying, as I had expected this to be a dual channel device. The only real upshot is that in order to use TrainerRoad, AND connect to my Garmin, I have use the computer ANT+ USB. I can’t connect to the computer over Bluetooth and the Garmin over ANT+.

The left leg only power I do constantly wonder about. I don’t KNOW what the difference between my RIGHT and LEFT legs is. I’d be interested if it’s significant. Neither the Stages, nor the Wahoo KICKR can give me this information, but both seem to give a reasonably consistent Normalised Power Output at the end of a ride.

It’s important to note, you can’t test just two power meters to determine accuracy. You need three, as who is to say which of your two is most accurate. I would love to have the kit to be able to do such a review, but alas I dont. DcRainmaker, and Road.CC both comment on accuracy, comparing multiple power meters toward the end of their reviews

You also then need to take into account their positioning on the bike. Due to drive train losses, a KICKR will always read a slightly lower power than a Stages. Also due to how the KICKR calculates power – based partially on speed changes of the fly wheel – there is a slight lag in power readings for the KICKR, whereas as the Stages tells you directly the force you are putting down the crank.

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Subtle looking crank

Personally I have found the normalised power readings at the end of a ride to differ by about 10-20watts between the KICKR and the Stages. Now initially that looks like a 5-10% variance, assuming aiming for ~200 watts average. But remember there are also the drive train losses in play here. So its usually better to compare crank power meters with crank power meters if possible. Or certainly those at that end of the bike!

The Stages cadence, is measured in the same way as the newer Garmin cadence sensors. No little magnet here, cadence is purely through an accelerometer inside the pod.

Stages App

The Stages app is very basic, and I mainly use it in order to update the firmware, and check the battery life of the unit – which interestingly tends to vary from my Garmin head unit – I have received a warning on the low battery from Garmin, but nothing showing on the Stages app. So I’ve taken the Stages app as the correct reading.

Interestingly the day AFTER my Garmin flashed up the battery was low, the power meter stopped working. However my ANT+ heart rate meter was also non-functional that day! The following day, both are working fine, and the app still records battery life as full. So I’m going to put that down to ANT+ gremlins, and say including turbo trainer, i’ve ride for 800km over 3 months so far without a battery change.

Garmin has updated their firmware to better show the power meter battery, but like many things on the garmin, its not very obvious! so I’m still looking for it!

Issues

The only other issue I have found with the Stages is occasional power spikes, but also the odd drop out. I don’t know what the cause of these are, and crucially if there is a major impact in the normalised power data.

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1779 watt spike – I wish!

This is something I have only noticed on outdoor rides, and will look further into using on indoor rides. It could be something to be addressed with data smoothing, or possibly an issue with the meter. I don’t know, but it is happening on many rides

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Second spike

Other than this, the Stages, I think has been a great starting point for a power meter. Would I ever move to a different power meter?

I like the idea of being able to migrate from one bike to another. So I’m not massively keen that I’m now locked into the Ultegra 6800 crank, but realstically how often will in want to move it between bikes? Plus, for the difference in price, e.g. To the Garmin vectors, that transfer easily, I could have purchased a SECOND Stages power meter

Conclusion

In the time I’ve had been using the crank for this Stages power meter review, I’ve found it much more helpful than that KICKR at promoting my training, as I know what my power is – or currently was – out on the the road.

Since I have been riding with a power meter, I’ve seen a real world improvement of about 10% in my FTP, as my sessions on the bike are not focused on keeping some arbitrary average speed.

So in summary, can I say the Stages is a good product- YES. Have my legs benefitted from it? – YES

I think the Stages is a great product at this price point. Personally I’ve love a dual sided power meter, as I think that would address specific cycling issues I have, but you can only buy to your price point. In which case this is a great start.

Just quickly in terms of price point. I am a great fan of eBay. But not for power meters. These are precision pieces of kit, with very narrow tolerances. I would not want to buy a used power meter, as even with a great seller, you can never be 100% sure of its previous life before you, and why its being sold. A first party power meter, comes with a warranty. In kit like this, thats crucial

27/04/2015 update

I have continued to get data spikes even after having returned to the clip less pedals. Initially I thought it might have been due to my foot slipping on the flat pedals.  ”

On the last ride you can see, this time on Speed Play pedals, I’ve another power spike, to 1057 watts, and then the battery ran out. I don’t know if this is likely to be connected to the battery or not. So the battery has been replaced, and I’ll repeat the ride and see what happens.

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 In order to look a little more about what happens with regard to the power spike, I’ve actually used a Fly6 to record the ride, and you can see where the spike occurs, and the battery fails. I’ll upload that clip later.

The Fly6 review will be due this week!

Update 17/05/2015

I contacted Stages about the power drops, and after sending a series of photos to the team there, they determined that I had an early batch battery door that was known to let the battery move, resulting in the drop outs. They sent me a replacement door – I honestly can’t see the difference, but the manufacturing dates are different, and the older door has “A” moulded into the plastic, vs “B” moulded into the plastic on the new door. More importantly on my ride today, it appears to have cured the dropout issue!

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Sliding doors
“A” top, “B” bottom

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James Gill

Author of TitaniumGeek, which started after smashing off my RIGHT elbow. Feel free to drop me a line about sports tech, medicine, or frankly anything that you want to chat about!!