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4iiii Innovations‘ new Precision 3 power meter is a slimmer version of its original crank-based meter, and one that comes with a claimed 800 hours of battery life and +1/-1 percent accuracy.
You can buy the left-arm meter installed on a Shimano crank — or send in your own and have a meter installed on it — starting at $324 for a 105 model. There are also Ultegra, GRX, and Dura-Ace cranks, in both stock and factory-install versions.
4iiii claims the strain-gauge unit adds just 9 grams to a crank, which seems about right based on 4iiii and non-4iiii cranks I’ve measured.
The plastic housing is 40 percent thinner than 4iiii’s previous meter, and an LED light gives color-coded information for when it’s being woken up (green), being calibrated (blue), and when the battery is running low (red). It takes a single 2032 coin cell battery.
It transmits on ANT+ and Bluetooth, like any modern power meter. The ANT+ ID is printed on the BB-facing side of the housing, which makes it difficult to see when on the bike. But for normal use, once you are paired to your head unit, you’ll never have to think about it again.
The meter has active temperature compensation, meaning you don’t have to recalibrate it on a ride when there are big swings in temperature to maintain its accuracy.
Further, you don’t need a magnet glued or otherwise attached to your frame as you do with a Shimano or SRM meter.
Aside from adding a new battery periodically and calibrating the meter with your head unit of choice, the Precision 3 acts and looks just like any left crank in terms of installation and maintenance.
Comparisons to other meters
The short story here is this: I came to trust the 4iiii meter, and would happily use it for training and racing.
I was unable to test the 800-hour battery life, which is an impressive claim. I can say that not all batteries are created equal, and whatever meter you are using, buy Energizer or Duracell, not cheap batteries.
I tested the Precision 3 against a few meters, but did the most testing with a Wahoo Kickr 5 and Speedplay Powerlink pedals, as I could use those simultaneously with the left-crank meter.
Some people are skeptical of one-sided measurement (where one leg is measured and that wattage is doubled), but I am not one of them. I often use a Stages left-crank meter on test bikes and my personal bike. (Full disclosure: I’m friends with — and ride and race with — many of the guys at Stages.) For super-short durations I sometimes see discrepancies, but for 10-second and up averages I seldom do.
For reference, a Stages Shimano 105 left-crank meter costs the same as 4iiii’s — $324.
Both 4iiii and Stages make dual-sided meters as well. And brands like Wahoo and Garmin offer single- and dual-sided pedal-based meters.
In testing against other meters and smart trainers, the Precision 3 rose and fell in synchronicity. As with any power meter testing, there was never an exact match in power for every single second. But the fact that the 4iiii was within my expected range of 2 percent or less to other meters was very encouraging.
The only hiccup I encountered was that the latest generation of Wahoo Elemnt Bolt could not find the meter when searching for a new sensor. An older Bolt, a slew of Garmins, my iPhone, and my MacBook Pro were able to find it without issue.
Bottom line: the new 4iiii Precision 3 strikes me as a solid power meter for a good price.