As one of the original backers of the LIMITS power meter, I finally received my unit in January 2017. I share the frustration of many backers concerning the information policy of the LIMITS campaign, particularly the absence of any firmware/accuracy related information since October. One core issue with the LIMITS power meter is its accuracy, another one its battery life. This website is dedicated to an open assessment of both.
What am I doing
My technical possibilities are limited. As a benchmark power meter, I can only use the Stac Zero power trainer, another crowdfunded project. DC Rainmaker wrote about it here. However, Stac Zero wrote to me: "Each time we've spot-checked against our quarq we've been just about dead-on with it (within 1W over an hour), but logic says we should be a few percent down since we're measuring post-drivetrain." Furthermore, Stac Zero delivered consistent power readings over a number of rides, showed no erratic behavior, and demonstrated instant responsiveness to power surges.
I don't own a Garmin head unit, but I'm usually tracking my training with OruxMaps. (I highly recommend this app, especially in combination with OpenAndroMaps. With my currently two-year old smartphone, I am able to ride 8-10 hours on one charge, depending on how much I use the screen.) OruxMaps does not store power data yet, because it exports training as .gpx files, so instead I'm using IpWatts. This app was programmed by the maker of IpBike to give DC Rainmaker a tool to read out power from more than one device simultaneously. From the raw output (instant power readings for either power meter), I can derive the difference between both power meters in watt, which gives a visually clearer idea of the magnitude of deviation between both power meters. Cadence data is recorded from my Garmin GSC 10 speed and cadence sensor.
All data files collected here have been sent to LIMITS support before publishing them on this website.
Why am I doing this
I'm no expert on interpreting power data, but maybe others are, and the data they see can generate helpful advice for the LIMITS team. I'm not affiliated with LIMITS - I do this purely for the sake of not having to throw away a unit that for its general concept which I still find intriguing: Assembly was simple and took me 10 minutes the first time, will take me at most 5 minutes every next time. One 10 minute ride after every bike change to get things settled plus calibration before each ride. This seems trivial to me compared with the installation most other power meters require.
Finally, it's compatible with SPD cleats, and there's nothing attractive to me in pure road cycling shoes, since being able to walk properly in my cycling shoes is a high-level priority for me. (I don't want more than one pair of shoes, and during summer vacation, my cycling shoes are also my evening shoes, so I have to carry less in the backpack.)
Just, it's worth nothing if the data doesn't add up. Also, I hope LIMITS sees that transparent beta testing can pay off, and generally responds by moving towards an open beta. I have no intention to do harm to LIMITS with this website. As a user of the product, I myself benefit of their success - or, more simply, survival.
How you can contribute
If you are riding on LIMITS yourself, and you do have another power meter at hand for comparisons, get in touch with LIMITS support (support@limits.technology). Please feel free to also get in touch with me and share your power data to be included in this collection.
This site is made with the new Google Sites for convenience. Since there's no comment feature included yet, I follow a common workaround by adding a Google Forms/Spreadsheet combination.
Q factor
LIMITS form factor means that it increases your Q factor, i.e. how far away from the pedal arm your pedal will be. This has an influence on your knee angle. For some people, this seems to have created problems. On my test rides so far, it has not (yet). I don't notice the difference on the trainer.
It will also reduce the angle you can take in turns while pedaling, so you will use your MTB cornering technique (since a Roadbike with LIMITS fitted has roughly the Q factor of a mountainbike). This might be a larger problem with crank arms longer than 172.5mm.
Personally, I'd be in the fortunate position that my cleats currently are mounted rather to the inside of the shoe, which therefore moves towards the left of the pedal center (on the left shoe). Had I changed the cleat position towards right of the center, LIMITS would not even have affected my Q factor. I would speculate that the different position on the pedal might alter power transmission, however.