4iiii Precision 3+ Pro power meter review: accurate and easy to use, but it has one weakness

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The Precision 3+ Pro is the latest crank-based power meter from 4iiii.

Built around high-end Shimano road cranksets, it costs £1,259.99 / $1,259.99 / €1,259.99 for this Dura-Ace R9200 version. That makes it a relatively expensive option in an increasingly competitive market, although there are ways to reduce this up-front cost.

Cost aside, 4iiii’s Precision 3+ Pro delivers accurate, dual-sided power measurement in a simple-to-fit package.

The only notable flaw is a potentially weak non-driveside battery cap design, but 4iiii’s lengthy three-year warranty helps alleviate any durability concerns.

4iiii Precision 3+ Pro specification

The 4iiii Precision 3+ Pro is designed to integrate cleanly with the latest Shimano road bike groupsets.

As with other similar options, such as the Stages Power LR, 4iiii’s dual-sided cranksets comprise two individual power meters measuring the output of each leg independently.

The Precision 3+ name denotes 4iiii’s latest power meter sensors, with the ‘Pro’ denoting it’s a dual-sided power meter.

Options

In terms of options, the Precision 3+ Pro is available as part of Shimano Ultegra R8100 or Dura-Ace R9200 cranksets, with crank lengths from 165 to 175mm and 50/34, 52/36 or 54/40t chainrings (54/40t chainrings are only available with Dura-Ace cranksets).

Prices start at £979.99 / $979.99 / €979.99 for Ultegra cranksets and rise to £1,259.99 / $1,259.99 / €1,259.99 for the Dura-Ace one I tested.

That’s a little more expensive than Shimano’s own FC-R9200-P power meter crankset (£1,199.99) and almost double the price of Favero’s Assioma Duo pedals (€695).

There are no 4iiii power meters for SRAM or Campagnolo groupsets, though, and only single-sided options for Shimano’s GRX and 105 R7100 groupsets.

The only differences between the Ultegra and Dura-Ace cranksets are aesthetics and 40g or so in weight – they should otherwise perform identically on the bike.

If you already own a 12-speed Dura-Ace or Ultegra crankset, it can be sent to 4iiii for a ‘factory installation’ of the power meter sensors. This cuts costs significantly, to £549.99 / $529.99 / €549.99.

In fact, given a Dura-Ace R9200 crankset costs £549.99 at RRP (and can typically be found online for less), you could buy one, send it to 4iiii for a factory installation and save at least £160.

Of course, doing this would take longer and be a more involved process than simply getting one off the peg, but could be worthwhile for some.

In any case, given 4iiii is presumably able to buy the cranksets from Shimano for less than in-store prices, it’s slightly odd that a complete power meter crankset appears to cost more than the sum of its parts.

Weight

4iiii claims the Precision 3+ Pro hardware adds only 29g on top of a standard, non-power meter crankset.

With Shimano claiming a non-power meter Dura-Ace R9200 crankset with 52/36t chainrings weighs 692g, 4iiii’s claim checks out exactly.

At 721g, it’s also noteworthy that the Precision 3+ Pro undercuts Shimano’s own FC-R9200-P power meter crankset (750g) on the scales.

Technical specifications and connectivity

4iiii claims the Precision 3+ Pro is accurate to +/- 1 per cent, and it reports advanced metrics such as left/right balance, torque efficiency and pedal smoothness.

On paper, this again outclasses Shimano’s own FC-R9200-P power meter crankset, which has a claimed accuracy of +/- 1.5 per cent, and matches the best power meters available.

The 4iiii Precision 3+ Pro has a claimed power measurement range from 0 to a monstrous 4,000 watts and can measure cadences from 30 to 170 RPM.

It offers ANT+ or Bluetooth connectivity for connecting to bike computers and smart devices.

Power is supplied by two user-replaceable CR2032 lithium-ion coin cell batteries (one in each power meter). 4iiii claims an exceptionally long battery life of “up to 550 hours”, which far outstrips most of its competitors.

In comparison, Shimano’s FC-R9200-P crankset offers a claimed battery life of 300 hours, via an internal rechargeable battery, while Quarq’s DFour DUB spider promises 200 hours of riding time and Stages 150 hours (both from CR2032 batteries).

Apple Find My

The 4iiii Precision 3+ Pro features Apple’s Find My geolocation technology, enabling you to register the power meter (and therefore whatever bike it’s on) with an Apple smart device as you would with an AirTag.

This could come in extremely handy should your bike ever get stolen or lost while travelling, because it enables you to track its location. 

Handily, because there are no Apple symbols, or anything clearly promoting this feature on the crankset itself, it’s also highly unlikely any would-be thief would have an awareness of the feature and the knowledge to thwart it.

4iiii Precision 3+ Pro installation and setup

The 4iiii Precision 3+ Pro is installed like any other Shimano road crankset, with no special tools required.

This means you’ll need a bike with a Shimano-compatible bottom bracket, along with a 5mm Allen key / hex wrench and a Shimano preload cap tool. It’s also recommended to use a torque wrench to tighten the two pinch bolts to 12-14Nm.

Unlike with Shimano’s FC-R9200-P crankset, there’s no need to attach a magnet to your bike frame, because the 4iiii measures cadence using internal accelerometers instead.

Given the simplicity of this process, transferring the 4iiii power meter between bikes is relatively easy – assuming compatible bottom brackets / drivetrains, and a match for things such as gearing and crank length.

In terms of frame clearance, the non-driveside pod is 5.5mm tall, meaning you’ll need space for at least an 8mm Allen key between your non-driveside chainstay and the crank to ensure compatibility.

4iiii says ENVE’s Melee and Fray road bikes are known to “present challenges” in this regard, but it also cautions that, “In general, bikes that have a wide/flared BB shell may have fitment challenges”. It’s therefore worth double-checking your bike before committing to a purchase.

Before connecting the power meter to your bike computer, it’s necessary to link up the two sides of the Precision 3+ Pro via 4iiii’s smartphone app (available for iOS and Android devices), so that data is broadcast from both cranks in one stream, but this only takes a moment.

It’s also sensible to apply any available firmware updates at this point, because these typically include bug fixes and updates that help improve data accuracy.

In my case, this meant upgrading both cranks to firmware version 2.3.0, which I used for the remainder of testing.

4iiii Precision 3+ Pro performance

On the bike, the 4iiii Precision 3+ Pro works just like any other 12-speed Shimano crankset, blending class-leading front shifting, impressive stiffness and quiet operation. The only difference is that power data appears at your head unit.

As I’ve noted before, there are inherent advantages and disadvantages to most types of power meters (the ‘perfect’ power meter doesn’t exist) and the Precision 3+ Pro is no different.

In this case, you’re tied to a specific bottom bracket, crank length, chainring bolt circle diameter and Q-factor.

The upsides, though, are that the electronics are well protected from crash damage, there’s plenty of room for large batteries and you get true left/right power data thanks to the presence of two independent sensors.

Weather sealing

My only area of concern is with the battery cap on the non-driveside crank. While the driveside battery cap is held securely on by three Phillips #1 screws, the non-driveside cap is simply held on by small tabs and friction, and twists on and off.

The amount of force required to remove it is surprisingly small – so much so that I unwittingly knocked it off while washing my bike for the first time after installing the Precision 3+ Pro. 

After leaving it to dry thoroughly, and reinstalling the battery and cap, everything has since continued to work without issue.

However, this poses questions about the cap’s long-term ability to resist the ingress of water or dirt.

It’s worth noting this isn’t just a problem with the specific crankset I tested either. The battery cap on a second non-driveside Precision 3+ crank (which we had in for First Look Friday in late 2023) can be removed just as easily.

4iiii’s website also has a number of reviews from riders complaining of lost or broken battery caps, confirming it’s not an isolated issue.

Should you lose or break one, replacement caps are available from 4iiii for £12.99 / $14.99 / €14.99, although this feels quite pricey considering it’s just a few grams worth of plastic plus an O-ring.

All that said, my colleague, Liam Cahill, has been using a non-driveside Precision 3+ Pro crank for around 18 months and hasn’t suffered any water ingress issues, so perhaps this is more of an issue in theory than reality.

For its part, 4iiii said this is something it has “had feedback on in the past (albeit not in huge numbers)”, and said it was working on improving this area of the power meter for future versions.

To the brand's credit, 4iiii power meters come with a three-year warranty, which is longer than most (even if three years isn’t that long in the life of an expensive power meter).

4iiii Precision 3+ Pro data accuracy

Back on to the positives, 4iiii’s Precision 3+ Pro displayed no issues in terms of data accuracy, consistently tracking other benchmark power meters and smart trainers without any obvious issues.

The numbers I got from it averaged a hair lower than a set of Favero Assioma Duo pedals and a Tacx Neo 3M smart trainer.

However, once you account for the respective error bands of each meter and the fact they’re all measuring power in different locations, everything still falls within spec.

All things considered, I’d have no trouble using the 4iiii’s Precision 3+ Pro to train or race with.

4iiii Precision 3+ Pro bottom line

Overall, 4iiii’s Precision 3+ Pro power meter delivers on the basics of hassle-free installation and accurate data, blending seamlessly with 12-speed Shimano road groupsets.

The long battery life and Apple Find My technology also help set it apart from the competition.

However you cut it, though, it’s a relatively expensive proposition and the non-driveside battery door design could be more secure.

If you’re looking for a Shimano-based power meter crankset, though, the 4iiii Precision 3+ Pro is a good option.

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