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The Power2Max power meter

29 May, 2013

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Background

There are many power meters for road bikes out there today. They come in roughly four different forms.  Crank based systems, like the well established SRM, often seen on bikes used by professional riders. The PowerTap wheel hub system.  Systems based on other components like pedals (Look Keo Power) and finally there is the category of less conventional power measurement solutions like the iBike.

I’m going to share my experience so far with my Power2Max so far. I’m not pretending it’s a review, since I own one of these systems and clearly the ‘review’ would be biased. What I can do is point out the good things, bad things, gotchas and general information about this power meter.  In the process perhaps correct a few incorrect reviews still posted out there on some major cycling websites. Having personally owned two other power meter systems (various PowerTaps and iBikes), I can compare the Power2Max. I’ll also cover the purchasing process for the Power2Max, since this is a little bit unusual.

About the Power2Max
The Power2Max is a crank based power meter system like an SRM or Quarq. Made by a small independent German company, it’s available in many different flavours to suit numerous cranksets both road and off-road. The Power2Max can be purchased with a crankset, or if you already have a compatible crankset then you can simply purchase the power meter only, which is of course cheaper.  You can find the complete range on the Power2Max website [ http://www.power2max.de/power2max.php?lang=en ]. You will notice that all the cranksets available are those with removable spiders (the part of the crank that the chainrings are bolted onto).  The Power2Max power meter replaces the original spider. Inside the casing of the Power2Max is the magic that measures the strain applied by measuring the twisting force on the chainrings. Depending on your crankset you may also be supplied with a tool to remove/refit the the manufacturers spider. For example for the Rotor 3D+ crankset, a splined tool rather like a large cassette tool is supplied to remove the original Rotor spider. This is not complicated process but the original spider can be a little tricky to remove.  A good video for fitting the Power2Max to the Rotor 3D+ crankset (if you purchased the power meter separately) can be found on YouTube [ http://www.youtube.com/watch?v=HX5pYF0eHXY ].  You can buy the Power2Max with various colour accents or in plain black (plastic colour).  For those in North America, the Canadian website  [ http://www.power2max.ca/ ] does a larger range of colour/effects.  Mine, pictured below is the no-colour option.

power2maxcrank

Rather than repeat a load of good information out there already,  I’ll point you to DC Rainmakers excellent in-depth test of the Power2Max over on his website. [ http://www.dcrainmaker.com/2013/01/power2max-power-meter-in-depth-review.html ]

Ordering the Unit
This is a little bit unusual for anyone not in Germany and I suspect is probably something that stops the company getting more orders. Power2Max units must be ordered directly from Power2Max. On the website you choose your crank/meter/colour and any accessories. You then enter your details and place your order.  After a short time, maybe a couple of hours you will receive a order confirmation containing the estimated shipping date (a week number).  On the order confirmation are the payment details for Power2Max. You must then set-up a bank transfer to Power2Max.  This is actually easier than it sounds within Europe and can be done through your online banking, but is a bit strange.  Apparently payment through bank transfer is common in Germany.

Recent posts on the Wattage forum from Power2Max indicate that they are looking into other payment methods. This will be a good thing. Hopefully the purchasing process will be more like any other online retailer.  Edit: I notice that the Canadian website now accepts Paypal but not the German website as far as I can tell. Hopefully this will happen at some point.

I didn’t receive a confirmation of my payment once made (however I did ask Power2Max for confirmation).  After four weeks, and as scheduled, the Power Meter arrived at my door. I was surprised that it takes 4 weeks for the meters but Power2Max explained that the meters are built and tested in small numbers as they are still a small (albeit growing) company and demand exceeds the ability to supply.

Using the Power2Max
Assembling the Power2Max is as easy as fixing the chainrings to the meter and assembling the cranks. I’ve already mentioned above that the Rotor 3D+ spider can be a little difficult to remove, so when fitting your chainrings make sure you get your chainrings aligned correctly. Once fitted you will need to remove the spider to refit them.  Regardless of what chainrings are fitted, the power meter does not have to be sent away to be recalibrated.  Just ensure the rings are installed to the correct torque specification as stated by the crankset manufacturer. This is a nice design feature.

There are no settings or anything to configure on the Power2Max itself. You will need to install a lithium battery into the battery compartment. This is a standard off-the-shelf button type battery. However it is NOT the standard CR2032 but something a little harder to find in stores, a CR2450N and it MUST be made by Renata. My guess is that this battery gives a longer life than a CR2032, as it is the largest button battery available. The cheapest place I have found to buy is from Amazon. The battery is found in the triangle battery compartment with the Power2Max logo. It is held in by three TINY little screws. I can guarantee that you will at some point lose one (or more) of these screws.  Power2Max thoughtfully provide 3 spares in the box, but it is well worth being VERY careful when fitting/replacing the battery.  It is also worth taking some time to make sure the double rubber seal is re-fitted correctly around the battery compartment to keep any moisture out (especially if you live in the UK!).

Power2MaxBat

The nice thing about the Power2Max is that actually using it could not be easier.  A spin of the cranks will wake the Power Meter up. Output uses the ANT+ protocol so any ANT+ compatible head unit of your choice can be used. I currently use a Garmin 800.  Calibration (actually Zero offset) of the Power Meter is automatic, but is always worth setting the zero offset by going into the  mis-titled calibration screen on the Garmin and selecting calibrate. The number displayed on the Garmin calibration screen is somewhat meaningless, but is the current offset reading. This number can change based on environmental factors such as ambient temperature so will vary from day to day or even from beginning/ending of a ride.

This brings me on the the single biggest thing that has been improved in the Power2Max range. It’s important to note, there are still old and inaccurate reviews out there. Early units prior to about September 2012 did not have temperature compensation hardware. This resulted in the readings being somewhat inaccurate under some circumstances. Since September 2012 this is a total non-issue since the hardware has been improved. The offset is now automatically adjusted to compensate for changes in temperature either before or during your ride.  If you do have an old unit they can be sent back to Power2Max HQ and fitted with the new temperature compensation hardware.

I’ve not owned one of the old units, but I can report that in my experience with the current model, power output is measured accurately and reliably. In fact this is what I love about the Power2Max the most. It is a case of just getting on and riding. No fuss!

The power readings are sent to the ANT+ head unit (in my case Garmin) and can be displayed in any number of ways. Post ride, the data can be downloaded to the software or web service of your choice.  Comparison of Power data in Golden Cheetah [ http://www.goldencheetah.org/ ] shows that power data from the Power2Max is comparable to that of my Powertaps and does not contain any weird spikes.  The head unit is updated every second, updates seem a little slower than with a PowerTap (i.e. after you press down hard it takes a tiny amount longer to register on the head unit).  However,  I’ve not had the two types of meter running simultaneously to compare, so don’t take this as fact.

Another nice feature of the Power2Max is that cadence is measured without the need for a cadence sensor. Unlike the PowerTap  which also has this facility, this is not estimated but is measured by accelerometers within the Power2Max. The result is accurate cadence. I’ve not seen a single weird number in downloaded data which occurred with a PowerTap reasonably often.

The Power2Max can measure left/right force and this data can be displayed on the Garmin or downloaded and analysed later.  In reality only one side is measured and the other calculated, unlike the Pioneer meter, or Rotor’s own power meters.  However the usefulness of this measurement is dubious. After all your pedaling style is your pedalling style. For all the talk of the advantages of souplesse there is counter-study that concludes it really doesn’t matter and Professional riders simply pedal harder. Time will tell.

Until particularly bad weather forced me back onto the turbo trainer recently, one thing that I never considered was that measuring speed on turbo or rollers will require an additional sensor. Unlike the hub based PowerTap, the crank based Power2Max (like all crank based systems) cannot measure speed.  ANT+ compatible speed sensors can be bought from many different suppliers (Garmin, Bontrager etc.). As mentioned previously you don’t need to measure cadence as this is already built in. As a side note, the Garmin 800 allows you to use ANT+ speed only sensors wheras other head units might not.

Conclusion
The Power2max is simple to use, robust and accurate. The price is very good compared to other crank based systems (especially for Campagnolo owners who don’t want to run SRAM or Shimano chainsets) and is very competitive with similar alternatives. The choice of the Rotor3d+ chainset means that I can run this meter on pretty much any bike, as it supports all common BB standards simply by changing the BB cups and spacers.  I run Campagnolo with round rings and the front mech shifts perfectly.  I like not having to be tied to a particular set of wheels.

If I have to pick some things that could be improved upon, then perhaps that there is no method to update firmware is one (although I would rather have no method than add a hardware port that makes the unit more suspectable to bad conditions).  Another minor point is the choice of a specific type and brand of battery, although this is being picky.

Some people have commented that there is no method of checking the units calibration. In my experience of trying to actually check the torque calibration of PowerTap hubs to see if they are still accurate after a year or more, I’m of the opinion that the results in a home environment are just not controlled enough to be 100% accurate.  Fortunately if you really are concerned your Power2max readings are screwy, the unit is small and easy to post back to Germany to be checked. It’s a lot easier than shipping an entire rear wheel.  The philosophy of the Power2max is to keep thing simple so in my opinion, this is acceptable. The Power2Max has a 2 year warranty.

To sum up, the Power2Max is reliable, easy to use and accurate. Although no decent power meter is cheap, it’s also cheaper than most alternatives. In all I am super pleased with it.

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3 Comments leave one →
  1. Peter permalink
    18 July, 2013 01:56

    Thank you for posting your experience.
    I too want to get into a power meter.
    And trying to compare the quarq with the power2max. But Im finding the most daunting piece of the puzzle is knowing which BB/crankset/chainring set-up to order. Can you tell me how you decided?
    I’ve a older Pinarllo ext. BB bearings. Carbon crank arms. 130bcd. Chorus 10spd.

    Thx.
    Peter

    • 18 July, 2013 11:43

      Hi. I was never going to mix SRAM and Campagnolo, so that left Rotor,FSA or one of the German brands as a choice of crankset. My Colnago has a normal 68mm English threaded bottom bracket, yours might be English or Italian. Rotor do make an Italian BB30 adapter called Rotor ITA30. If you have 130mm BCD chainrings then I guess you’ll want that again, unless you want to switch to Compact rings for climbing.

      • 18 July, 2013 11:48

        Oops, hit send. So the answer is one that fits your bike and your philosophy. I like the Rotor 3D+ as it is compatible with many different standards by just changing the bb cups. The weight is also pretty good and spares are easily available, at least here in the UK.

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