Precision Power Meter Review

4iiii Precision Power Meter Review

At a Glance: Quick Ratings

Ease of Installation


Value for Money


Battery Life


Ease of Battery change


Where To Get It

A Deep Dive Into 4iiii Precision Power Meter

The 4iiii Precision power metering crank arms have been reviewed by Tristan Haskins for This is the product I personally used kindly sent to me from EvanCycles.

Crank Arm based power meters are the simple to install requiring just an Allen key and a Shimano crank arm removal tool (about £2/$3). 4iiii’s power cranks are very popular among cyclists wanting to break in to power metering and not too worried about power balance.

They measure power from the LEFT leg only and provide a TOTAL power figure based on the power from this one side.

The objective of this product presentation is to provide an overview of – what the product does, who’s it for, how easy it is to fit and how much it costs …

  • Who are they For?

  • Pros & Cons

The 4iiii Precision Crank arm power meters are for the cyclist content with single sided power metering without feedback on left & right pedal balance.

They are simple to move from one bike to another (assuming same crank / length). With a quoted accuracy of +/- 2% they are more than good enough for the majority of keen cyclists. Key features of this product are – ease of installation, affordability, accuracy and a solid battery life (approx 120 hours from a CR2032).

The product is supported by a competent 4iiii iPhone/Android app with feedback on battery status and the ability to Zero calibrate (shown above).

If you’re in to cycling you may have heard of a Slovakian cyclist by the name of Peter Sagan … yep that Peter Sagan. Well Peter and his 2021 team ETIXX QUICKSTEP use the 4iiii Precision products for all their power metering data collection.

A little endorsement from one of the world’s greatest ever road cyclists is surely confirmation of how great their products are.

Method of Installation

Installing the 4iiii Power Crank is a doddle .

You may need to buy a crank removal tool like this Shimano one (external link) if you don’t already have one.

The only other tools required are an Allen key.

  1. Simply remove the crank arm cover with the special removal tool, it should be hand tight only.
  2. Then unscrew the two opposing Allen keys from either side of the crank arm.
  3. Once these are removed the crank arm should be easy to remove from the axle.
  4. Grease and carefully fit the 4iiii Precision crank arm. Ensure they are at 180 degrees to the other side.
  5. Hand tighten the crank cover screw then start tightening the Allen keys.
  6. Once they start getting a bit tight do one side, then the other, then the other and repeat, alternating side.
  7. If the crank arm cover is easy to remove and you have no issues, it should take less than 10 minutes !!

Tools Required to fit this Power Meter

Watch the Video

A short video showing how to install, set up and pair your 4iiii Precision Power meter crank. In this video I pair the 4iiii Precision with a Garmin Edge 820, Suunto Spartan Ultra and Polar M450 (M460)

Test Ride Data & FTP Test

After spending less than 10 minutes removing the old crank and installing the new 4iiii Shimano 105 power meter it was time for a quick spin. I used my Garmin Edge 820 to perform an FTP test. Everyhthing worked perfectly and I look forward to my next POWER METERED road ride with the 4iiii power meter.

Alternative Power Meters

There are now several other competent brands producing power metering cranks. At the time of writing this review none covered as many brands and models of crank as Stages. However, the most popular cranks from Shimano (105, Ultegra and Dura-Ace) are all catered for by 4iiii Precision and Pioneer.

Take Advantage of Normalised Power

If, like me, a lot of your riding is interval based with short periods of hard effort then you’ll soon realize Average Power is a fairly useless metric. A ride consisting of 5 x 5 minute intervals @ 300 Watts is a seriously demanding session, hopefully helping to improve my sprint endurance. However, such a ride could result in an average power reading of less than 100 Watts.

Similar to Average Heart Rate, this figure is not-indicative of the physiological effort employed throughout session. That’s why Allen and Coggan devised Normalised Power (ext). Normalised Power (ext) takes in to consideration the physiological stresses imposed on the body’s energy systems providing a more useful metric. An interval session like the one previously described may result in an average NP figure of 225 Watts.

Normalised Power is a convenient way of comparing dissimilar training sessions and understanding the physiological system being trained. From my own training, the rides with Avg Power very close the Avg Normalised Power tend to be cardiovascular / aerobic improvement rides. Those with an Avg NP in excess of 50% of the Avg Power are generally Speed Endurance sessions. Those in between tend to be my Tempo paced rides.

GPS Bike Computers with NP

Currently (May 2021) the best value for money GPS bike computers (ext) that support Normalised Power is the Garmin Edge 820 (ext) and the new Polar M460 (ext).

Technical Specification

  • 3D power meter technology (patent pending) measures tri-axial strain on your crank arm
  • Accurate, consistent data
  • Lightweight, compact design
  • Battery status indicator via 4iiii app
  • Compatible with ANT+, Bluetooth Smart head units, smartphones, and other 4iiii products
  • User-friendly app and configurable rider compensation scale factor
  • Easy setup and maintenance
  • Weight: 9 grams
  • Data accuracy: +/- 1% error margin
  • Battery life: 100+ riding hours on 2032 coin cell battery
  • External Resources

    The purpose of product presentations is to give the visitor a summary overview of each power meter. They are NOT intended as an in-depth technical review, more a summary providing essential top level features, functions, pros and cons. Further information can be found at these links to other external reference sites.

    Product Summary

    The 4iiii Precision Power Meters are available for Shimano Dura Ace (9000), Shimano 105 (5800) and Ultegra (6800).

    The Power metering technology is installed on the rear side of the crank arm face keeping it safe from damage and interference. Installing these power meter cranks is easy, simply replace your left hand crank arm and you’re ready to ride. Available in Black/Silver only with a choice of 170mm, 172.5mm or 175mm crank arm lengths.

    At the time of writing this review these 4iiii Precision cranks are the worlds lightest left side power meter.

    They have been designed to provide industry leading power accuracy with highly dependable cadence  & power data. Supporting both ANT+ and Bluetooth smart head units and 3D power meter technology capable of measuring tri-axial strain on your crank.

    Firmware Updates from smartphone

    When paired with an Android device / iPhone running the 4iiii Precision App will prompt when a firmware upgrade is available. 2 minutes later and the power meter’s firmware is up & running with the latest firmware.

    The app also gives useful feedback on battery life.

    Simple Calibration / Zeroing

    The 4iiii Precision pedals can be reset to a factory default Zero power setting in just a few seconds.

    Just spin the pedals a few times to wake them up, then, without your feet clipped in, point the leg crank arm directly down (6 0’clock position).

    From either your bike computer (Polar, Garmin etc) or the 4iiii app select the calibrate / zero option. It’s that simple. On my Garmin Edge 820 it provides the following useful response codes :

    • 10 – Good, ready to ride
    • 20 – Unstable data (bike not stationary)
    • 30 – Low battery (less than 10%)
    • 50 – Calibration error – contact support

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