Review: Power2Max MTB Power Meter

I think it’s human nature to love new gadgets. No doubt early humans were thrilled to get their hands on those advanced Neanderthal tools. Recently I received one of the newer kids on the power meter block for my MTB; the Power2Max Rotor 3D+ crankset. For those of you not familiar with Power2Max (P2M), they are a German based company, with North American distribution housed in Western Canada. The general design is similar to the SRAM Quarq spider, but with a great deal more ability to choose or retrofit existing cranks. Pricing is competitive, and set-up is touted as one of the easiest to set-up.

By this time, nearly everyone knows what a power meter is and has likely seen one. Further, numerous reviews have been done on all of the power meters already, however, few have looked at mountain bike (MTB) specific power meters, or even how to use the data gained from those power meters. The objective of this review is to look at the P2M MTB meter from out of the box set-up to ease of use and ultimately durability. In follow-up post, I will discuss downloading and using the data, and later this season, present some race data. So with that, below is what you get out of the box.

This is what you get out of the box.

This is what you get out of the box.

A close-up of some beautiful cranks.

A close-up of some beautiful cranks.

I look inside the box; everything you need to set up your power meter.

I look inside the box; everything you need to set up your power meter.

Note the calibration certification and notes on torque specs.

Note the calibration certification and notes on torque specs.

Everything you need to set-up the pre-assembled P2M is provided (minus the screwdrivers). This includes the battery, the pressfit bottom bracket bearings, manual, crank decals, and even the tool needed to remove the power meter spider. Also, the first page of the manual displays the calibration certification.

Once you unbox the P2M you will need to install the battery by removing the cover. These instructions and more are all clearly detailed in the manual provided, which you should read prior to removing the battery cover. Why? Unlike other power meters, P2M pairing with your head unit of choice (in this case a Garmin 500) takes place right after you install the battery; once you pop it in, a green LED flashes for 20 sec, which is when you pair the unit. Once pair, install the cover back on and you’re reading to put the cranks on the bike.

Removal of the battery cover is a snap. With the new battery in, you pair it with your head unit.

Removal of the battery cover is a snap. With the new battery in, you pair it with your head unit.

A well written manual with detailed instructions.

A well written manual with detailed instructions.

Sadly, or perhaps fortuitously depending on how you look at it, I forgot to take pics of the crank installation process; in truth, this review is about the power meter more than the crank. Suffice it to say, the easiest part of the set-up was behind me, and installing the pressfit bearings provided specifically for Rotor cranks went smoothly and required only a little tapping with a rubber mallet. The real fun started after that, because unlike other cranks on the market, Rotor has taken a simply, relatively easy task and turned it into a convoluted mess. Beautiful and light cranks they are, simply to install they are not!

The issue starts with a manual apparently written by a team of former IKEA employees. The pictures are minimally helpful and the text is of little additional aid. The second pain in the a$$ are the multiple aluminum spaces provided for the BB axle interface; a standard BB30 would have external bearings that widen the actual BB width. The spacers in theory should allow you to install the cranks on many different bikes and BB widths, with the spacers allowing you to make up the “play” and prevent over tightening the cranks against the bearings and making for an impossibly tight BB; ie, you pedals do not turn. This is actually a common problem with Rotor cranks. Complicating the matter further, Rotors direction may indicate that you need extra spacers that they do not provide, as in my case; I actually needed a second .5 mm spacer, but was able to mix and match the others to find a combo that worked. I cannot tell you how annoying it is for a company to make an expensive product then tell you after you buy it you need to buy a glorified washer that costs about $0.10 for $10-15 (I actually don’t know what they cost). The crank design is quite elegant, but the self extracting cap system makes the set-up much more time consuming. Once set-up, though, follow-up installation will be a snap and the cranks are pretty sweet (pictured below); a little bit of pain for some pleasure, I suppose. I would also like to note that Rotor offers greater crank size options, which I took advantage of, moving from the ubiquitous 175 mm cranks to 172.5 mm. Interesting research on MTBers indicates that going slightly shorter may actually improve clearance and acceleration without impacting leverage. I never liked 175’s and I’m glad to be rid of them!

Once on the bike, the P2M looks great and does its job.

Once on the bike, the P2M looks great and does its job.

As I stated earlier, though, this review is about the power meter, and so its important to note that once the cranks are on the bike you are ready to hit the trails. My first ride was a pretty tame skills session largely due to weather and time constraints. I wanted to be sure the power meter was working and the cranks would fall off my bike before this year’s Monster Cross.  Some salient features of the P2M meter include:

  • auto calibration (technically an auto correct of the zero off-set) when you stop pedaling for 3 sec or more.
  • It also auto corrects for temperature, which is particularly important when you ride during changing temperature periods (cold mornings to warm afternoons).
  • power2max power meters don’t need a magnet to calculate cadence as the power mater calculates it internally.
  • ANT+ Standard – the popular and reliable standard that gives maximum compatibility.
  • Left-right balance pedaling comparison (more on this later)

Power2Max in Action

I figured there would be no better test for the P2M than the fast, hilly Monster Cross. All I wanted to address for this initial review was does the P2M hold up in competition and what does the data look like; ie, is it useful. I cannot discuss actual validity because I do not have the ability to install this on a mechanically braked research grade bike, like a Monark. However, in the real world, close to actual numbers are fine for training purposes so long as you only compare those rides with other rides using the same device; ie, I can’t draw direct comparisons between my SRM, Quarq, Power Tap (1 & 2), and the P2M. I can, however, make qualitative comparisons, and draw some general conclusions in regards to training, which I will do later this year as I train and race MTB, XTerra & Road tri’s, and road training.

Below are four power file views from the race including the full file (blah, a spaghettified mess) and a break down of laps 1 (21 miles), 2 (8 miles), and 3 (21 miles). As anyone can see, the beginning of the race was typified by huge power swings for the first 30 min, after which I drop off the lead group out of commonsense! Again, without external verification I can only draw on my experience to judge the P2M’s validity. As a training tool these numbers are precisely in line with where my training/fitness are, currently. One thing of significant note is that despite seeing very high power outputs on my head unit, its clear, and unsurprising, that MTB power fluctuations are large and frequent, owing to the changing terrain, surface, 29er momentum (yeah, trying to sit on a group riding cross bikes is much more difficult than you would think), and the usual ebb and flow of pacing. One key factor in MTB analysis is eliminating spikes in power and reducing average power per lap, while decreasing time; you want to be as fast AND efficient as possible.

The complete power file from the 2014 Monster Cross.

The complete power file from the 2014 Monster Cross.

Lap 1 is an undulating 21 mile loop. Note the early violent efforts in the lead group.

Lap 1 is an undulating 21 mile loop. Note the early violent efforts in the lead group.

A shorter 8 mile loop splits up the race.

A shorter 8 mile loop splits up the race.

Lap 3 repeats the first loop. While peak are lower, the lap was still very stochastic because a few riders failed to ride a steady pace.

Lap 3 repeats the first loop. While peak are lower, the lap was still very stochastic because a few riders failed to ride a steady pace.

As a note, lap 3 was 30 W lower and 6 min slower than lap 1, owing more to me trying to manage my cramps than true fatigue. Once I dropped off the lead group, I rode with various groups and individuals always maintaining a comfortable pace for myself and only extending myself when needed. In truth, I was making up a lot of time by cutting corners tight, faster descending and better trail skills, which brought me back onto several groups. In the end, cramps sealed my fate on one of the late climbs (~2:25:00). However, the Power2Max worked flawlessly in what was a hard, muddy outing.

To recap, out of the box the Rotor Power2Max brings a great deal of aesthetic appeal. While the power meter itself is a snap to set-up, the crank installation is a bit of a pain and probably best left to a bike shop. The fact that Rotor does offer more crank size varieties is a big plus in my book, though, and once set-up they are a very nice set of cranks. The price of the P2M is very competitive, and will continue to be so as the newer light models emerge. The P2M function is excellent and the automatic calibration and temperature correction are both convenient and helpful for MTB riding, where conditions change frequently.

Crank weight comparison:

SRAM XO 175 mm Crankset was 640 g plus BB (not weighed)

Power2Max Rotor crankset is 760 g plus BB (not weighed)

My initial rating (largely based on function): A 

 

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