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The Power2Max power meter

29 May, 2013



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 [ ]. 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 [ ].  You can buy the Power2Max with various colour accents or in plain black (plastic colour).  For those in North America, the Canadian website  [ ] does a larger range of colour/effects.  Mine, pictured below is the no-colour option.


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. [ ]

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!).


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 [ ] 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.

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.


Removing Powertap Hub Shell

22 May, 2012

If you have a CycleOps PowerTap hub on your bike, one thing you will need to do from time to time (maybe once a year) is replace the batteries in the hub shell. There is a special tool available for doing this, but many people report that they are afraid of rounding the shell off using the proper tool as they are unable to get enough leverage.

The solution is something like a Boa Constrictor tool. Essentially a rubber strap wrench. This tool will allow you to undo the shell and tighten it up without any risk of rounding and little risk of shell damage (just don’t over torque the hub shell when you tighten it back up!). It can be a little tricky to get working initially as it is a little too large for the small hub, but once you have some purchase on the hub shell it is very easy to undo and tighten.

Mine cost about £6 / $9 at my local hardware store but they are available on the web.

Boa Constrictor Strap Wrench

Performing the upgrade to Cyanogen on the HTC Desire HD

4 October, 2011

OK these are the notes I made to myself whilst doing the upgrade to the ROM on the HTC Desire HD. Unlike my other guides, this is not a set of step by step instructions but will give you everything you need to know, especially if you have a vague understanding of Unix type commands and can set environment paths on the Mac/PC. IMPORTANT: Follow them at your own risk. My phone was an unlocked device, if you have a contract mobile tied to a provider you will need to perform some extra steps not listed below during the upgrade process (Google “creating a gold card for HTC Desire HD”).

You will need to install the Android development tools. Specifically you need Android Development Bridge (ADB) which allows you to send commands to a connected phone.

1. Follow instructions here and here to install ADB to gain temporary root and backup phone using Titanium

2. Install stock ROM. My phone had ROM version 2.50.405.2 on it, need to downgrade to 1.32 to permanently root the device with Flash recovery and enable future ROM updates. Followed the Cyanogen Wiki here

Tip: On a Mac you can use the shell/terminal command “MD5” to validate the files that you download using the MD5 hash (note firmware archive MD5 does not match according to Wiki MD5sum)

3. Used guide here for downgrading ROM in place of the Cyanogen ones as my phone was already on Android 2.3.x… then continued with the Cyanogen Wiki guide. If your phone is still on 2.2. you’ll need to do something different.

4. Cannot do second part of the Cyanogen guide, so used Visionary+ technique here instead and then this

Tip: had to do chmod permissions on the phone’s terminal app (which I downloaded from the Android Market) rather than using adb shell, for some reason adb wouldn’t play for me.

5. Installed Clockwork ROM Manager from Android Market. Choose CyanogenMod7 stable and also checked install Google Apps.

Tip: My phone constantly rebooted after the Cyanogen logo, I had a boot loop! so booted into ROM Manager (power + volume down) and reinstalled Cyanogenmod again from zip on SD-card file after deleting system caches and davlik caches using ROM manager option.

6. Installed Google Apps from zip file menu using Clockwork Recovery Manager

I now have a nice stable HTC Desire HD with CyanogenMod7

Upgrading HTC Desire HD to Cyanogenmod 7

2 October, 2011

The washing machine ate my was a sad and expensive day. One positive thing is that I did give me the opportunity/excuse to try out an Android device. After a bit of ebay scouting I found an unbranded (SIM free) HTC Desire HD, which I got for a decent price. Though not the latest HTC Android device, the Desire HD is a nice phone, although physically large due to the massive screen.  The only downside of the Desire kit is the poor 1200mah battery supplied. If you use the phone heavily you will only get a few hours out of it.  Fortunately another check of ebay uncovered third party 1800 mah batteries for about £8!  These are a huge improvement and the battery concern is sorted.

The Desire HD has everything you could want and to my mind, a bunch of iPhone beating features, like expandible storage via mini-SD card and a replaceable battery, it features all the other stuff that you would expect (multi-touch screen, GPS etc) and transferring data back and forth to a Mac or PC is so much more convienent than using iTunes. Simply tell the phone to connect to the PC/Mac and it will appear as a removable drive.   A nice feature is that you can tell the phone to charge only if you don’t want to transfer data so don’t need to eject it.

HTC supply their phones with some software enhancements (at least in their eyes) to the Android OS, known as HTC Sense. It’s basically extra features, apps (mainly geared around social networking) and some interface skinning. It’s all very pretty.

However, I’m one of those people that likes the bare minimum and then add what I want to add.  I also want full control of the device I am using. So after looking into things I decided to ‘root’ my new phone and install Cyanogenmod, a custom ROM which is closer to stock Android 2.3 (with some sensible concessions).  There are a numerous postings on the internet about how to root the phone and install a custom ROM, however I did not find a single one that worked (my ROM revision was much later than most of the postings). By combinining several threads, a bit of knowledge and doing some digging, mission was finally accomplished.

I now have an HTC desire HD just the way I like it.  To be fair to HTC, the whole process will be much easier on newer devices. HTC recognise that users may want to root their phones, the ROMS supplied on new devices now support this.  Shame other companies don’t actually listen to what their customers want.

I’ll post up the steps I took in the next post.

Hatred of the file system

11 September, 2011

The iPad is a wonderful device. Having been on holiday recently, I realised just how much this device is changing the way computers will be from now on. Books, photos, movies, games and where available – internet access. All to hand in an unobtrusive, portable format with a highly intuitive user interface. Brilliant.

However the more I use the iPad, the more I start to bang against the ceiling of Apple’s deliberate imposed limitations of the hardware and software.

Why is there no SD-Card slot built in to the iPad? OK so you can use a £25 adapter, but then even worse…no access to the file system. So, without Internet access, how does one backup the contents of the iPad exactly, or transfer files? Why can’t one simply copy files to an attached SD-Card using a file management utility. Why isn’t it possible to simply Bluetooth files to a more flexible device?

Sure there is the excellent iFiles App which allows something akin to a file system and provides Wifi file transfer, but transferring many or large files over Wi-fi is SLOW. iFiles also doesn’t provide access to physical media.

The answer is of course crystal clear. Apple want control of your device and data (and of course your cash). If you want to put something on your Apple device you have to go through the laborious iTunes sync process, visit the one and only Apple app store or use iCloud (or whatever it’s called this week). Ultimately the aim is to remove the file system concept and control the content. No doubt much of this is to appease the media companies, however wrong.

Personally, I’ve never understood the disability of the Cuppertino outfit to provide “advanced” options, even if it voids some kind of warranty. The end result is a constant battle with Hackers, desperate to make the iPad work the way any sane person would want it through a process called Jailbreaking. Instead Apple could embrace the needs of many different users quite easily, but as always it’s their way or the highway.

Having recently been forced to switch to an Android phone from my now dead iPhone I’ve realised just how limiting iOS actually is. As usual Apple treating their users as stupid.

It is rather sad and somewhat pathetic that the tablet war is being fought by lawyers instead of letting the best technology. I suspect Android tablets would become the device of the tech savvy.

Mac OS X Lion – Lion or Lemon?

21 August, 2011

SadFinderSo the day Lion was out, I downloaded it from the App store. It was most unlike me, since many years of experience have taught me that the initial releases of Operating Systems are usually a bit flaky and it’s often best to wait for the first wave of patches. Still Snow Leopard worked well on release and so I thought Lion would too.

Oh dear, I had a long list of I thought a complete reformat/reinstall would do the trick. After all upgrades often leave behind all kinds of legacy junk.

So I made sure everything was backed-up (twice) and reinstalled from fresh, using a DVD I had made using the download from the app store. Stupidly, the installer for Lion is normally deleted once Lion is installed (Seems Apple don’t want you to actually possess anything in the future – a post for another day), but I took a copy of the program beforehand and made an installer DVD with it. Instructions to do this are on CNET here. Only any use if you have a “legacy” DVD writer.

So a nice fresh install on the iMac. So what’s good about Lion? Nothing, yes I mean zilch. Honesty, I haven’t found a single thing that I prefer over Snow Leopard and I have a long list of things that are just not right. Edit: In the interests of fairness, yes I remember one now – you can resize windows from any corner. Whilst I like this new ‘feature’, it’s something that every other OS has supported forever.

Now this isn’t a review, but basically a moan. As far as I can tell, OS Lion is a essentially a bigger, slower and dumbed down version of Snow Leopard. It’s something that those of you might not notice on your zippy new Intel i5 & i7 machines. For those of use with older Core2 computers, get used to the spinning beach ball. I’ll post another day about what I think Apple’s intentions are, but for now lets concentrate on this lacklustre software release.

My list of gripes goes something like this. Where I have found a workaround, I’ve posted it. If you have any tips please share them below. The list is in no particular order.

1. Can’t connect to the web through web browser when machine wakes from sleep

I can ping my router and I can resolve names through DNS but I can’t get to any website using Firefox, Safari etc. Seems like this actually a Firewall issue. For some reason the Firewall by default is off. The problem is when the firewall is enabled (and really you should have it on) and the machine wakes from sleep, any web browser doesn’t work.

Workaround: Turn the firewall off, go to any old website and then turn it back on. The web browser will now continue working.

Update: This seems to have been fixed in the first set of patches released from Apple, they only mentioned Airport WiFi but the patch also seems to fix wired connections too.

2. Apps folder missing from Dock by default.

If you are upgrading from Snow Leopard you won’t notice this. But when a fresh install takes place, we are expected to use Launchpad instead of having apps in the Dock. Pleeeaze.

Workaround: Use Go->Computer from menu and then navigate to hard drive. Drag the applications folder to the dock.

3. Finder problem: Downloads folder columns not resizable or sortable in details mode

Seems to be the only window in the OS that you might want to sort frequently (say by type, size or date) and can’t. You cannot resize the view columns either.

Solution: The default option is to sort the downloads finder window by date.  This prevents the columns from being resized.  From the menu bar select View ->Arrange By->None.  The downloads window in Finder will now have resizable columns and will allow you to click on the column headers to sort in whatever method you desire.

4. Finder problem: window contents are often jumbled initially

You view the contents of a folder and the icons are all jumbled and on top of one another. Seems to happen mostly on mounted disk images.

Workaround: You have to tell the Finder window how to sort, every time. Get used to it.

5. Finder problem: does not remember view settings, and does not obey globally set values (like open details)

Workaround: None, just get used to setting it every time.

6. Finder problem: Does not remember toolbar settings

Workaround: None, just get used to setting it every time. I hope you like repeating yourself, I do.

7. Finder problem: does not relinquish control of mounted disk images. Finder must be forced to quit to eject them sometimes

If you use a third party tool such as “What’s Keeping Me” or commands in terminal to see what the hold-up is, My bet is it will be Finder.

Workaround: Use Force Quit from the Apple menu to kill Finder. You can then eject your disk image (Finder will restart)

8. Lion is much slower: Preview is painful, beach ball waiting or pauses in Finder, system memory usage is higher. Machines limited to 4GB are hurting.

Apple are a hardware company. You wanted to upgrade that hardware, right?

9. Spotlight: can’t right click and open files in finder.

In Snow Leopard you could right click on a file result in Spotlight and select Open in Finder instantly. This option has been removed. This is a big backwards step. Spotlight has gone from being THE best search tool in the Personal computer world to almost useless.

Partial Workaround: Hold down CMD key on your search result for about 5 seconds, to see the file location and then go and manually navigate there.

10. Home folder missing by default

Doesn’t it make sense to have your home folder on the Dock? Maybe not and it’s just me…

Workaround: Use Go->Computer from menu and then navigate to hard drive. Drag your Home folder to the dock, right click and display as Folder

11. You can’t see the library folder

Yeah so it’s a system related folder. I thought Mac users were tech savvy. Seems like you are in fact too stupid to be trusted with seeing this folder so Apple have kindly hidden it. Side effect is that some third party apps have broken or require workarounds (e.g. VMWare Fusion)

Workaround: Hold down Option / Alt key to see this in the Go menu in Finder

10. Mail: Tries to auto configure mail and fails.

Workaround: The new mail program tries to set-up mail accounts and partially fails. For NTL/Virgin media Follow my instructions here to fix.

11. Versions/Autosave.

You are too stupid to remember to press save. Therefore Apple have removed the option for you. What’s that? You didn’t want to save your file? wait, you wanted to call it something else? You should have thought of that first, stupid. Am I the only one who doesn’t like this? Why can’t I choose when to save things? at least give me the options.

Workaround: None

12. Startup time is slower than Snow Leopard.

Even when applications are not set to re-open. The saving grace is that OSX doesn’t need rebooting too often.

Workaround: None.

13. Spaces (Virtual Desktops) are less functional

I like to have multiple desktops. In Snow Leopard I could select the virtual desktop I wanted by selecting it from the top right of the screen or jump to a specific desktop with a key combo. I could also send an app to another desktop by clicking the title bar and pressing ALT+desktop number. Nope can’t do that now. Seems that now, I am supposed to press F3 and bring up “Mission Control” and then select the desktop I want. Sure I can drag windows from one desktop to another but it’s all less efficient.

Workaround: CTRL+LEFT ARROW or CTRL+RIGHT ARROW allow you to switch to another desktop. There is no workspace number indicator.

14. The other Apps that don’t work properly on Lion

…such as Firefox which is now completely unstable (versions 5.x and the new 6.x). Yes, this last one is of course not the fault of Apple but it helps drive me nuts. Time to find an alternative browser.

In Summary

To me, Snow Leopard feels like a dumbing down the OS with bonus added bugs. The upgrade is only around £20 but frankly, if you have Snow Leopard I think you are paying for a downgrade. Do yourself a favour and spend the money on something else.

Update: Here is a good piece on Gizmodo that I came across. It pretty much sums up of everything that is wrong with OSX Lion. Saves me repeating the same thing

Campagnolo Brake Pads 2011 onwards

9 June, 2011

Campagnolo made a change to the brake pad holders in their high end groupsets for 2011. This new style pad holder is fitted on the 2011 Chorus, Record and Super Record brake calipers.  The design is brilliant. Changing pads really was a pain in the backside previously, requiring much effort. Now it really does only need a couple of minutes to change all 4 pads. Simply lift the spring clip holding the brakepad in place using a small flat screwdriver and then slide the pad out (and they really do slide out). This is wonderful for those of us using carbon wheels who need to change pads more often (or swap them if changing back to an aluminium rim).

The problem comes with obtaining replacement pads. The spring mentioned above sits in a small hole on the back of the brake pad. Brake pads prior to 2011 do not have these, so you cannot use them.  However, there are answers:

If you want to fit third party pads,such as Swissstop yellow pads, then for 2011 brakes you will need: “2011 SwissStop RacePro Yellow King Brake Pads for Campagnolo”.  If buying, be careful that these are the 2011 models and they are RacePro pads (RacePro = Campagnolo compatible). The actual SwissStop part number is: 7640121221729. SwissStop yellow pads can be used on either Alu or Carbon rims. However I personally would not recommend using them on both carbon and alu wheels, since small bits of metal may get embedded from the aluminium rims and then ruin your carbon rims if you swap between wheels. The other thing I don’t like is the yellow colour of the pads, but of course, that’s a personal preference!

The second option is Campagnolo’s own brake pads. Personally, I prefer OEM pads, especially the recently improved Campagnolo pads.  Now the fact of the matter is that these are actually available. The problem is that Campagnolo have introduced the new style 2011 pads with the little recess for the spring clip on the rear, but have not changed the part number from the 2010 pad. Discovered, no thanks to large online retailers (who are of little help).  Campag part number for Carbon rims is: BR-RE701/2. Update:  I never realised Campagnolo pads for Shimano Dura-Ace brakes are also available! For carbon rims part number: BR-701X/2

Fortunately, a real world bike shop (Sigma Sport) actually checked the pads and sold me pair of carbon specific ones. Funnily enough, that’s the second time this shop has helped me out…the first time was obtaining my Colnago C59 Italia almost a year ago. Thanks guys.

Campagnolo 2011 Brake Pad Holder