• Competitive Cyclist

4iiii Precision 3+ Pro Power Meter In-Depth Review

4iiii has just released its latest power meter, the 4iiii Precision 3+ Pro dual-sided power meter. Admittedly, at this point, the naming scheme has gone off the rails (see the chart later), but from an underlying product standpoint, it’s firmly on the rails and on point. So that’s (mostly) all that matters around these parts. And when it comes to power meters, the most important bit being: Is it accurate?

However, the second most important bit when discussing a new product is: What’s new?

In the case of the Precision 3+ (with the “+” part being the new part), that includes a substantial boost in battery life (up to 550+ hours claimed, compared to 100+ hours previously for the dual-sided version), as well as Apple’s FindMy integration built-in (which you can now share an object’s location with friends/family, effectively allowing them to track your rides easily). Additionally, they’ve added something called ‘Automatic Terrain Selector’, which roughly speaking aims to be more responsive to things like cobblestones versus silky smooth roads.

I’ve been riding the 4iiii Precision 3+ Pro the last month for a slate of rides, mostly focused on road and occasional gravel and cobblestones, as well as plenty of indoor trainer rides too. Ultimately, I’ve been putting it through its paces to see how it handles versus a slate of different trainers.

Finally, note that this unit is a media loaner, and once this review is complete, it will go back to 4iiii (along with a pile of other beta units they’ve sent). As always, I don’t accept advertising from any company I review – so, if you found this review useful, consider becoming a DCR Supporter, which gets you an ad-free site, plus the behind-the-scenes video series between both myself (and my wife) on everything that happens in the DCR Sports Tech Cave/universe.

What’s New & Models:

These days, when it comes to power meters, the changes are incremental at best. Simply put, power meters are a mature industry. There’s only so many new features you can add. Which does not however mean there’s a guarantee of accuracy, from new or existing companies. Every new model power meter needs to be evaluated individually.

Nonetheless, when it comes to features, the Precision 3+ Pro does have a few notable ones, specifically when viewed in the lens as a dual-sided unit (versus their single-sided units, which have gained some of these features already):

– Added Apple FindMy support: This basically makes it an Apple AirTag, including the ability to share that device location with specified friends/family

– Added Terrain Selector: I’ll dive into this feature a bit more down below, but essentially it changes the chipset components used in real time when it detects rougher terrain conditions. When the pavement is smoother, it turns those bits off to save battery.

– Increased battery life to claimed 500hrs: Previously, the claim for the dual-side was listed as “100+” hours. I haven’t been able to realistically validate this claim, given that’s an absolute crap-ton of riding. Note the unit uses CR2032 coin cell batteries, which I prefer as it makes replacements easier.

– Added support for Shimano Dura-Ace 9200 cranksets: Of course, that’s really the big ticket item here from a component standpoint, helping you avoid Shimano’s own flawed Shimano R9200P DuraAce power meter, yet still using  the same crankset.

– Reduced thickness (profile) to 5.5mm from 7.5mm: This is specifically compared to the previous dual-sided unit. Albeit the non+ version prior did get the left-side-only variant down to 5.5mm

– Being launched on Specialized bikes: Specifically, Shimano-equipped Specialized S-Works Tarmac SL8 and Aethos models will feature this power meter as an option. This follows a many-year-long partnership with Specialized.

From a pricing standpoint, it’ll depend on whether you want so-called ‘Factory Install’ or ‘Ride Ready’. Factory install means they install it on your existing crankset, whereas ‘Ride Ready’ means that you just unbox a brand new crankset and off you go (which is what I did here). Here’s that pricing:

Now, pricing aside, understanding the 4iiii power meter naming scheme has always required a decoder ring. Or, more like a decoder atlas. I’d strongly suggest for their next gen power meters, they change the name somehow and get rid of all the + & Pro addendums. They’re just unnecessary and add confusion. The number of times in this post I typed 4iiii Precision+ 3 Pro or 4iiii Precision 3 Pro+ or some variation thereof would impress you. I’m sure I got it wrong somewhere in here too. And from a business/Google search standpoint, the complexity in the naming greatly hurts brand awareness.

In any case, here’s the table from them on how each model works out:

4iiii Power Meter Comparison Chart.

The TLDR there is that if it has ‘Pro’ in the name, it’s a dual-sided unit. And if it has “+” in the name, it’s their latest generation. No idea what happened to Gen 2, maybe they only count odd numbers in Canada.

Personally, being a Canadian company, I think they could just call it the 4iiii Poutine Power Meter, which frankly would probably earn them enough viral news stories to kickstart them quite well. Don’t worry, I won’t charge licensing fees for the naming rights.

In the Box:

In my case, the unit sent for review was a fully boxed pre-installed crankset. That means that I didn’t send in my existing bike’s crankset for review, rather, effectively this was buying a new one. Point is that the process is different if you sent in your own crankset, though, I’d imagine the parts you get back would be exactly the same (since it’s basically just the crankset).

Inside the box you’ll find the crankset wrapped carefully in paper, ready to go from squeaky clean to quickly covered in sweat, road grime, and all manner of sports gels and drinks. And if the unit is destined for a long-course triathlete’s bike? I’m sorry in advance.

In any case, inside the box you’ve got a little flyer about the unit, some install paperwork, then the drive-side crank arm (that’s the right side one with the chainrings installed), as well as the non-drive side arm (the left side). There’s the small cap that you use to seal it all up. Oh, and a sticker.

Here’s a look at the cleanest this left-side crank arm will ever be, including the 4iiii pod installed on it:

Meanwhile, on the right side, you’ll see the pod just under the inner ring, and the wiring ‘tunnel’ connecting to the battery pod compartment towards the upper right. You’ll notice the ANT+ ID listed on it (45298), which is the right-side ANT+ ID. The left side has one too, though once you connect to either side, it pulls in the information from both sides.

So, with that, let’s get it all installed.

Install & Setup:

Installation is pretty easy here. Shimano road cranksets are pretty much the easiest things to install on your bike, assuming you’re swapping from an existing Shimano crankset. I will caution that if you’ve got some other crankset on your bike, and aren’t super familiar with bottom bracket standards and such, that you should probably have your bike shop validate you’ve got the right parts. Else, you’ll spend a lot of time and headache till you’ve got all the right parts and tools to get the right bottom bracket in there for it.

But, if you’re just swapping Shimano for Shimano, my 7-year old daughter can do it. You merely need an Allen wrench, potentially something soft/rubber to lightly whack the crankset out if it’s being stubborn, and then ideally some grease to help it stay happy. And, since Shimano/4iiii didn’t include a tool for that little cap (here, you can buy one on Amazon for like $10), you can use a flat-blade screwdriver in a pinch.

In any event, you can see above I’ve removed the existing crank arm. You can find instructions on the internet on how to do that, but all you need to do is:

1) Loosen the only two bolts there are, on the left-side crankarm
2) Remove the little plastic cap (you can likely do this with your fingers, or at worse, said screwdriver wedged at an angle)
3) Take off the left side crank arm, and then just push the right side, with the spindle, out from your bike. If it’s being a bit sticky, just lightly tap it with a rubber mallet to get it to come out.

Now, we’re ready to put the new one in. Apply a bit of grease to the spindle, anything too much and you can simply just wipe it away after you slide it in.

It’ll look like this. Pro Tip: Don’t forget to hold the chain up over it. Else, you’l complete install the whole thing and swear a bunch, realizing you forgot to get the chain in there.

Next, install the left side crank arm, which should only fit perfectly when exactly opposite the right side.

The order of operations for installing a left-side Shimano crank arm is:

1) Ensure it’s nice and snug
2) Then install the plastic cap to pull the two sides tightly together
3) Then finally tighten the two bolts, ideally working one after another, not just tightening one entirely and then the next entirely.

Donezo. Oh, install some pedals first. Then, donezo. Now…you’re ready to roll.

Daily Ride Usage:

With everything all configured, it’s time to pair it up to your bike computer or watch (or, app). The 4iiii units will pair across both ANT+ & Bluetooth Smart, with multiple concurrent connections allowed as well. This means that you can basically pair it to any device out there that can talk with power meters. In my case, I’ve tested it with both Garmin watches and bike computers, as well as Wahoo bike computers, and Apple Watches. I’ve also validated enumeration in Zwift and TrainerRoad. But again, it uses industry-standard connection types, so there shouldn’t be any issues here.

Looking at it on a Garmin bike computer as an example, you’ll search for the power meter. You’ll want to connect via ANT+ ideally, rather than Bluetooth, as more standardized information is sent via ANT+ than Bluetooth on the power meter side. There’s nothing wrong with Bluetooth per se here, it’s just that the ANT+ data stream includes added information like pedal smoothness and torque effectiveness, not seen on the Bluetooth side.

Once paired up you can name it whatever you’d like. You won’t/shouldn’t need to provide a crank length setting here, as it’s not a power meter pedal.

You can also double-check the battery here, as well as firmware versions:

The next thing you’ll want to do is a zero offset. On most bike computers/watches, this will be listed as ‘Calibration’, which is sorta-correct. Technically speaking, calibration is a bit different, but for our purposes, we’ll just call it that. Zero offsetting should be done without any weight on the pedals (no shoes clipped in), and still (no movement).

It’ll think for a few seconds, and come back with a success confirmation. In the case of 4iiii, success numbers are 1010, where basically the first two digits show the status for one side, and the second two digits show the status for the other side. You can find those status codes here.

As a general rule of thumb, you should calibrate before a ride – ideally once your bike has stabilized for about 10-15 minutes in the new temperature. So here in winter, it’s best to either let your bike hang outside for a few minutes before hitting calibrate, or simply calibrate 10-15 minutes down the road after both you have warmed up and your power meter cooled down.

With that done, we’ll start pedaling. As we do so we’ll see our power broadcast on the head unit of our choice. Of course, you’ll have needed to add a power meter field or two, to the bike computer. But most bike computers will actually offer to add these automatically when you pair a power meter for the first time. Here you can see power and cadence displayed. I have no idea why I elected to make cadence that gigantic:

Generally speaking, I’m looking at either 10-second or 30-second power. This means the power is smoothed for that duration. This doesn’t impact recorded data (which is still at 1-second intervals), just what you see. Power meter data, by nature, tends to be kinda jumpy, so most people will use at least a 3-5 second smoothing, if not more. I generally think of 10s power as my instant power.

In terms of responsiveness, I didn’t have any issues here with responsiveness on this unit. We’ll dive into that more down in the accuracy section though. In many ways, power meter reviews are kinda simple (at least, when they work). It’s essentially two basic questions: What and how does it transmit? And then, “Is it accurate?”. Sure, there are other bits like battery performance and crankset compatibility, but the biggie is really accuracy.

In any event, given it’s a dual-legged system, you’ll see power balance displayed too:

Further, you can also display torque effectiveness and pedal smoothness if you’d like. In total, the 4iiii system displays/transmits the following metrics:

– [ANT+/Bluetooth] Total power (combined left/right)
– [ANT+/Bluetooth] Power Balance (left/right split)
– [ANT+/Bluetooth] Cadence (RPM)
– [ANT+] Torque Effectiveness
– [ANT+] Pedal Smoothness

From there, any other data is calculated on your bike computer (e.g. 10-second power is simply the bike computer calculating that). Same goes for things like normalized power, average cadence, total pedal strokes, etc…

All of this is then recorded in the file, and you can view it after the ride on your bike computer, or from various apps from those companies. Here’s what that power data looks like on Garmin Connect, using any Garmin bike computer or watch:

And lower down that page, you’ll see those Torque Effectiveness and Pedal Smoothness stats as well:

Frankly, very few people will leverage those last two stats…but hey, they’re there if you want them.

One of the newer features on the 4iiii unit is the so-called ‘Automatic Terrain Selector’. This feature essentially aims to ramp-up usage of internal hardware components when it detects rougher terrain, and then put those components back to sleep when things are more like silky smooth roads. Generally speaking, rough terrain has always been somewhat challenging for power meters, though that’s largely been solved in the last few years.

Nonetheless, 4iiii says the new feature (which was previously launched on 4iiii single-sided units, but this is the first dual-sided one), should help in edge cases. From a tech standpoint, they noted:

“The automatic terrain selection was released on the non-drive side last summer but we have continued to refine and have filed for a patent on the tech. Prior to PRECISION 3 firmware version 1.2 we only utilized the accelerometer even though the gyro was physically part of the IMU.

All firmware’s since the IMU wakes up on startup and during zero offset and both accelerometer and gyro are part of the zero. During periods of rapid cadence change the gyro my engage in any environment where the accelerometer-based algorithm detects suboptimal conditions and then during periods where the IMU is being shaken violently (washboard gravel, cobbles, rumble strips that kind of situation).

Under the hood our system has a kind of “shake o meter” if you will that takes all the above items and a few more inputs and if the combined end output exceeds the threshold we have set then it activates the gyro and if it is less then it remains in accelerometer mode and therefore conserves battery life.

With this platform we have always had a vision for adding more features and making it a means to deliver customer solutions beyond just a great training tool which is why we are obsessed with minimal current draw and optimization.”

In terms of real-world accuracy impacts, again, I’ll cover this in the accuracy section below. But I repeatedly rode my bike over both cobblestone sections as well as off-road and gravel paths, and didn’t see any outlier in those areas. Especially notable are high-speed cobbles and bricks, which can have a high-frequency vibrating effect, but again, I didn’t notice any issues there. Given this was a road-bike groupset, it wasn’t used in any sort of crazy MTB rock-filled terrain, but for just about anything you’re going to encounter with a road bike (including some short off-road adventures), I tried to cover it.

Now, in terms of batteries, the unit uses two CR2032 coin cell batteries. These batteries are found round-the-world easily. 4iiii claims 500 hours of performance between battery swaps. As you might imagine, I don’t have that much time yet on this unit to validate that claim, and given the detail-level on the batteries themselves, I can’t really even estimate if it’s trending towards that. My main concern here isn’t so much whether it hits that claim, but whether they sacrifice anything else to hit that claim.

In previous releases, 4iiii has tried to push the boundaries of battery life claims to such an extent that there were ANT+/Bluetooth dropouts to watches and bike computers. But they’ve since realized the errors of their ways, and pulled things in a bit. Nobody really cares about having 700 hours instead of 500 hours, when the power data is dropping out. The good news, is I saw no dropouts at all on any watches or bike computers on this unit. So all seems well.

In terms of changing those batteries, for the left-side (non-drive side), you just simply rotate the little battery cap:

And then for the right side, you’ll need to undo the three screws to access the battery compartment:

It’s as easy as that. And given the 500hr claim, this won’t be something you need to do very frequently. Even if you were doing 10hrs of riding per week (which for most people is a lot), then you’d still be looking at basically a year’s worth of battery performance. Which is obviously pretty astounding. Heck, even half of that is still astounding.

It’s worth mentioning that 4iiii does have an app for doing checking and calibration of the power meter. It’s also here where you can update firmware, de-pair and re-pair the two sides together, and even record data files (via phone). In fact, 4iiii even has an Apple Watch app that will record power meter data and does a pretty darn good job of it too. Of course, with Apple adding native power meter support this past summer, there’s less reason to use other apps. But it’s there.

Here you can see the unit listed, as well as battery status:

I can tap to zero offset if I want:

As well as tap to get details on the system and firmware versions. There’s the pairing option as well, in the event you need to break-out and re-pair the unit. Again, nothing earth shattering in here, but appreciate it’s there if you need/want it. Most people will never use this, except to set up Apple FindMy integration, which we’ll dive into next.

Apple FindMy Integration:

4iiii first rolled out Apple’s FindMy integration about 18 months ago, shortly after Apple announced compatibility for 3rd parties. This essentially turns your 4iiii crankset into an Apple AirTag. What’s cool though is that last summer Apple added the ability for you to share your AirTags and other ‘FindMy’ things with specific people. Previously you couldn’t do that. Thus this allows you to essentially share your bike with friends/family (without perhaps sharing your own location the entire time). This can be useful for riding buddies.

Now, I can hear the complaints already “I’m on Android! Why isn’t 4iiii supporting me. I hate 4iiii!” (Seriously, that’s actually exactly what people said when 4iiii announced this previously)

Look, 4iiii was actually the first company to support Chipolo some 5 years ago in the power meter scene (which supported Android). And what did everyone do? Not care one single bit. Seriously, in every post/video I made about it, nobody cared. Like almost negative interest level. Said differently: When 4iiii did exactly what people asked, nobody actually supported them.

In any event, my mini-rant over, let’s get to the tech. To set this up, it’s pretty easy. You’re going to remove/replace the battery three times in a row, which then triggers the FindMy activation feature (and a blinking blue light on the power meter, indicating it’s in that mode). From there, you can go ahead and search for it from Apple’s FindMy app on your phone:

At this point you can give it a name, as well as a preferred icon:

After which, you’re done. It’s ready to go. You’ve got access to all the regular AirTag features in terms of finding things. Though, it won’t chirp like an AirTag will. But frankly, if you lose your bike in a couch cushion…that’s on you.

And, as you can see above, you can share it too. In this case there’s GPLAMA’s 4iiii unit that he’s shared with me. I’ve of course zoomed way out, to protect our various locations.

Certainly, there’s benefits in this if your bike is stolen, as most people won’t realize the power meter has an AirTag in it. And of course, you can remove the battery (though, a few more steps to do so with the right-side). But in terms of a quick getaway, most people won’t be reaching down to unscrew the battery compartment while stealing your bike from a cafe in front of you. Instead, this will give you a bit of tracking to do exactly what every police department tells you not to do: Chase that mofo down!

Or, it’ll just tell your family where your bike is, in case you crash and they can’t seem to locate you. Your choice.

Power Accuracy Testing:

I’ve long said that if your power meter isn’t accurate, then there’s no point in spending money on one. Strava can give you estimated power that’s ‘close enough’ for free, so if you’re gonna spend money on something it shouldn’t be a random number generator. Yet there are certain scenarios/products where a power meter may be less accurate than others, or perhaps it’s got known edge cases that don’t work. Neither product type is bad – but you just need to know what those use/edge cases are and whether it fits your budget or requirements.

As always, I set out to determine whether this unit is accurate and precise. In power meters today, one of the biggest challenges is outdoor conditions. Generally speaking, indoor conditions are pretty easy to handle, but I still start there nonetheless. It allows me to dig into areas like low and high cadence, as well as just how clean numbers are at steady-state power outputs. Whereas outdoors allows me to look into water ingest concerns, temperature and humidity variations, and the all-important road surface aspects (e.g. vibrations). For reference, the 4iiii Precision 3+ Pro has a claimed accuracy rate of +/- 1.0%.

I’m going to go through most of these relatively quickly, unless there’s a specific issue. You can click on any of the data sets to look at the underlying data yourself, if you’d like.

First up, let’s start with something simple – an indoor ride – an ERG workout in TrainerRoad. This one is actually on the Wahoo KICKR CORE smart trainer, and Favero Assioma Duo dual-sided pedals:

As you can see above, the green line of the KICKR CORE is settling down a bit during the warm-up, however, the two power meters (4iiii & Favero) are like best buds here, virtually identical across the board.

If I look at the left/right power balance split of one section later in the workout, you can see they trend very closely to each other. On the 2nd interval shown below, when my left leg is a bit lower there, you can see it matches on both of them that way. This is one area we’ll keep coming back to in this review. With dual-sided power meters, it can be somewhat challenging to get a bunch of them to agree exactly every time (to other units), but we want them to be pretty darn close – as total power on these units is simply the left side + right side added together.

Next, looking at cadence, again we see the units are virtually identical – save the KICKR CORE’s estimated cadence being a bit slow in some cases, which is normal for smart trainers using estimated cadence.

And then lastly, when we look at the mean-max power graph, which is a great way to see accuracy and alignment over longer periods, we see the two power meters are near identical, with the KICKR CORE a bit higher due to that earlier warm-up phase where it was reading higher. Still, on the whole, this is actually a very pretty chart.

Next, we’ve got another structured workout, some 30×30 tests, which is a good place to look at both trainer and power meter responsiveness. This is a quickie I do with all power meters and trainers, so I won’t spend too much time on it here. Nonetheless, here’s the data (note: the colors have changed here, sorry!):

As you can see, again, near identical. The singular exception to that though is the first moment of the first interval, which seemed to catch the Favero unit a bit off guard and got a bit excited. The other units didn’t report that level of excitement.

In any event, looking at the left-right splits on a few intervals, you can see again, Favero and 4iiii are virtually identical here, especially once power is applied. We see a hair-bit more separation at some of the lower levels while soft pedaling (e.g. 90w), which can be somewhat common for power meters.

Looking at the mean-max graph, we do see more separation here at the top-end, due to the excitement shown by the Favero unit early on. Again, unclear to me if that’s real-excitement, or fake-excitement. I’d argue it wasn’t real, but it can be difficult to suss out those slight nuances.

Now, let’s move from a structured workout to a non-structured trainer workout. This time in SIM mode, or simulation mode, where it’s simulating the terrain gradient in Zwift:

I know, it’s kinda a mess – such is life (and real-world pedaling). So, let’s zoom in on a few sections, starting with that sprint towards the end there. Looking at that, we can see very good alignment between the three units. There’s really not much to complain about here:

And if I look at that exact same timeframe, but now the left/right power, you can see again, they’re virtually identical between the two units. We see the Favero hold onto the sprint about 1 second longer than the other units (both above/below), which contributes to the average from Favero being slightly higher. But that’s not likely to actually be a Favero problem, but rather the simple reality of 1-second intervals for transmission/reception/recording rates (a blend thereof), driving these data differences. Said differently: It’s not likely a real-world data usage issue, just a recording/comparison issue.

Here’s another sprint, where we see the Favero and 4iii units separated quite nicely (in a good way) on the left/right side, with both of those respective sides aligned together:

We’ve then got a blah-boring cadence graph, with things basically perfect:

And also a blah-boring perfect mean-max graph. Frankly, you won’t get much more perfect than this, save a tiny bit of differences on the KICKR CORE:

So, let’s head outside, and start to toy with things a bit. Here we’ve got a relatively efficient road ride, and looking at the overall plot, obviously, it’s a bit variable:

So, let’s zoom in on a few sections. First up is this section here, which looks very close. Again, the reality of power meters is you’re going to see very slight differences of opinions, especially outdoors. But this is pretty darn close:

Here’s another section, again, with very slight differences here as we’re later in the ride:

And then if we look at the left/right split of that same section, it’s very very close – save a few seconds here or there we see slight disagreements. But it’s nearly impossible to know in this scenario which one is ‘most’ right. And as we can see above, practically speaking, it’s just not mattering – the total power is so close between them.

If I look at cadence, all seems identical there. There are two brief moments where cadence drops out for about 3 seconds on the Edge 1040 recording the 4iiii unit. However, this wasn’t just cadence dropping out, but all sensor data. I had a backup recording of the 4iiii on the Apple Watch (via Bluetooth), and I didn’t see the drop-out there. Thus it’s unclear to me if that’s an Edge 1040 thing, or a 4iiii ANT+ thing that happened.

And finally, the mean-max for that ride:

Next up, another outdoor ride, this one with some cobbled sections, some off-road sections, lots of road sections, and some sections I spent trying to figure out where TF the road went to. Here’s the data:

Now, I want to focus in on a few things with a bit more pickiness. Here’s a zoomed in section that’s virtually identical, for a half-hearted sprint. You can see there’s some slight disagreement on the ramp itself, but they basically get to the same spot.

And if you look at the left/right power split there, you see the two actually disagree about how I got there. The 4iiii says I had more left power, whereas the Favero says I had more right power. In total, both agree, but individually, they disagree on the composite of that.

Likewise, this section here. These two units are very similar, albeit the Favero is edging just slightly higher in some spots. Not a ton higher, but just barely higher at higher wattages. Or, one could say the 4iiii is edging barely lower in some higher-wattage spots.

You can see again that these two disagree on how that composite should be, but agree on that main sprint (point highlighted above), that the total power is the same but the left/right balances are quite a bit different for that exact second in time. Welcome to power meter analysis!

In some ways, going down the above rabbit hole can be never-ending.

However, where it becomes concerning is when a pattern develops between differences in total power. And there is a slight pattern here on some rides (but not all rides), where the Favero unit is a bit higher than the 4iiii unit:

And if we look at the breakouts there, we notice the 4iiii is reading slightly lower, primarily on the right side, than the Favero pedals. Again, this doesn’t happen often, but happens mainly on surges. Sometimes. But not every time.

Again, I can go multiple rides in a row where this doesn’t happen, but then you find a ride where it does happen – and I don’t really have a great reason for it. For my riding and power output, it doesn’t seem to be a major concern, and seems to be fairly minimal, but it does have a slight effect on higher wattages for your total power curve. You can see that here. If I look at the mean-max point for the 10-minute  section, the two units are only a couple of watts apart (totally normal). But as we climb higher and higher, they diverge more.

Finally, one last ride from today. In this ride, I was heavily focused on trying to break things. So, I just went out along the rowing basin and sprinted 1,000w repeats over and over again. My goal here was to see if I could cause the right-side to do wonky things. Also, for funnies, I swapped out the Favero pedals for a pair of Garmin Rally RK200’s. I trust both the Favero and Garmin pedals equally, so this seemed like a good next step.

Here’s that fun (with no smoothing applied). That empty chunk about 1/3rd of the way into it is doing some zero offsets and photos:

Now, as you can see pretty obviously, these all look really darn similar at a high level. However, there are some slight differences when you zoom in.

You’ll notice that it’s almost as hard to see those differences here too though. These are very very very close. What’s interesting is that it seems like the Rally is a touch bit higher each time, but in reality, they hit about the exact same point each time, just about 1 second difference. You can see the 4iiii has a smidge bit more smoothing applied as I increase power into the interval, which contributes to the slightly higher overall averages you’ll see in a second. But again, let’s be clear – this is astonishingly close for 1,000w sprints.

If we look at the left/right breakout of this same section, you’ll notice that sometimes Rally/4iiii agree exactly on the breakout balance, and sometimes they don’t. What’s funny though is that they both come to the same agreement on total power. So…yeah, not sure how to reconcile that.

And finally, the mean-max power. Here you’ll see Rally is slightly higher. I suspect that’s because if you look above, Rally has slightly less smoothing, so it tends to be a bit jumpier as I apply power, giving it a bit of an additive power surplus over the course of the ride. Very slight, but you can see it here more-so than other rides since all I did was sprint repeats.

Anyways, overall, I’m not seeing any accuracy issues on this particular unit with all of my riding or pedaling styles. As always, that can vary from person to person, or even unit to unit sometimes. But in terms of overall accuracy, this seems to stick the landing on both power and cadence accuracy.

(Note: All of the charts in these accuracy portions were created using the DCR Analyzer tool. It allows you to compare power meters/trainers, heart rate, cadence, speed/pace, running power, GPS tracks and plenty more. You can use it as well for your own gadget comparisons, more details here.)


When it comes to Shimano-based dual-sided power meters, particularly for Shimano’s newer cranksets, it’s been somewhat slim pickings. Shimano’s own power meters offering is, of course, notoriously inaccurate (even with the most recent updates), and that’s largely left you with Stages and 4iiii offerings. Thankfully, both of them seem solid with recent models. In the case of Stages and their Stages LR dual-sided unit, I’d been riding that for quite some time without issue, though I’ve got concerns with the company’s viability and complete and utter lack of customer service department for the past 6-8 months. Which is too bad, as the company has historically been quite solid.

Meanwhile, 4iiii seems to have both a power meter that’s accurate – and a company that’s financially viable with people answering phones and all the normal things that you do as a company in the power meter space.

For Apple users, having the FindMy feature is a nice touch, if for nothing other than peace of mind. Given how cheap it is to put an AirTag on your bike in other places, it’s probably not a feature you’d individually pay a ton extra for – but when it’s there, it’s handy. Meanwhile, 4iiii’s ‘Automatic Terrain Selector’ feature seems to do nothing user-facing visible, which is pretty much exactly what I want in a power meter feature. Meaning, I don’t really care how a company arrives at an accurate value, as long as they do. 4iiii could call it ‘Poutine Mode’, and I’d be happy, as long as when I hit those cobblestones or rough patches, it stays accurate. And here it does exactly that.

Ultimately, I don’t really have any meaningful complaints. My biggest gripe is simply the name is just far too confusing. But that’s not a product problem, rather, a marketing one. And it’s certainly not my problem. And from a consumer standpoint, it’s realistically not a problem you care about either, as once it’s on your bike, you’re just gonna call it the ‘4iiii power meter’.

With that, thanks for reading!

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Hopefully you found this review useful. At the end of the day, I’m an athlete just like you looking for the most detail possible on a new purchase – so my review is written from the standpoint of how I used the device. The reviews generally take a lot of hours to put together, so it’s a fair bit of work (and labor of love). As you probably noticed by looking below, I also take time to answer all the questions posted in the comments – and there’s quite a bit of detail in there as well.

If you're shopping for the 4iiii Precision 3+ Pro Dual-Side Power Meter or any other accessory items, please consider using the affiliate links below! As an Amazon Associate I earn from qualifying purchases. It doesn’t cost you anything extra, but your purchases help support this website a lot. Even more, if you shop with TPC (The Pro's Closet), you'll save $40 on purchases over $200 with coupon code DCRAIN40! The Pro's Closet has been a long-time partner of the site here - including sponsoring videos like my cargo bike race, as well as just being an awesome Colorado-based company full of good humans. Check them out with the links below and the DCRAIN40 coupon!

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Thanks for reading! And as always, feel free to post comments or questions in the comments section below, I’ll be happy to try and answer them as quickly as possible. And lastly, if you felt this review was useful – I always appreciate feedback in the comments below. Thanks!

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  1. tfk, the5krunner

    Impressive battery life and ty for the review

    Is the “Terrain Selector” triggered like the one that Stage has which uses a gyroscope?

    • Benedikt

      It reads for me as if it’s the same technology, but on my Stages I had to choose if I wanted it permanently enabled or disabled.

  2. Mike Gagliano

    That’s disappointing news about Stages as I just purchased one a month ago. Hopefully they right the ship. I did the factory install and it was a quick turnaround though.

  3. Changren Y.

    Perhaps you meant to write CR2032, instead of CR2023?

  4. Ray, typo in the second to last big paragraph: “4iiii’s ‘Automatic Terrain Selector’ feature seems to do nothing user-facing visible, which is pretty much exactly what I want in a power better feature.” I think that should be “power meter feature”.

  5. John B

    I’ve been curious about Stages as well. Own and love an SC3 spin bike and a Stages power meter. I love how high quality their stuff is. Have you considered investigating and doing a blog post on them?

    • Benedikt

      I had a Stages and needed to replace the left crank. Their Battery compartment is a bit finicky to close without damaging/displacing the sealing O-Ring. I did talk to some others and that problem was much more common than I thought.
      But Service was superb and fast.

    • Andrew B

      I have Stages L on my CX bike which has been fine for about 4 years.

      I have Stages L-R Ultegra on my road bike, since September, and am in the process of sending it back for the second time.

      Both times, the R side started under-recording, seen through the L-R balance becoming 60-40 or worse. The calibration (which should be about 900 ish each side) went to about 1200 on the R, and the app showed a 10 degree temperature difference recorded between the two sides, although they were on the same bike.

      Not sure if others have had problems?

    • Bernhard

      Stages support told me that the temperature difference doesn’t matter as long as it stays roughly the same when the ambient temperature changes. So if the left side read 10 degrees and the right sight read 20 at about 22 degrees room temperature and then 0/10 at 12 degrees outside for example, it should be fine.

      Did you have the temperature difference on both units and was it the same? Mine read about 7 degrees apart.

    • Andrew B

      All three units I had came with a substantial temp difference. Stages may be right that it does not make a difference. If so the cause must be elsewhere as all three started generating crazy numbers on the L side after a couple days/ weeks/ months depending on which unit

  6. Frederick Norton

    any chance there is a gravel crankset version coming to market any time soon?

  7. brett

    I don’t know why you’re so blasé about torque efficiency (TE). In fact, we should call it Torque Efficiency Data Dynamics Yaw to make it more marketable. My reading is that ‘teddy’ is a measurement of how much one pedal stroke is directed towards driving the chain forward, and that any figure less than 100 indicates that some of your power is being siphoned off and applied against the resistance of your other foot.
    Current studies have discredited the idea of actively pulling up with your hamstrings, but unweighting your foot will increase your teddy and free up watts to be directed in driving the bike forward rather than pushing your opposing pedal out of the way, surely a desirable metric.
    hug me🧸

  8. Benedikt

    The Find My integration was the point to choose the 4iiii over the Stages when I switched bikes last month.

  9. The Real Bob

    I have 5 4iii single sided power meters. 2 old models and 3 of the brand new models I just had factory installed to my cranks. My two older models were the ride ready, where you just purchase a crank arm with it installed.

    4iii is a fantastic company, they answer phones, respond to emails which is lacking in most companies. My two older models have worked flawlessly for several years. I had garmin vector 3s that were just nothing but problems from day one. I had a Giant dual sided power meter that was horrible also, although I liked that it would give me like 5 w/kg FTP (in my dreams).

    Ray is correct, single sided power meters are all most of us need. It gives you the most useful data for amateur cyclists. I never really did anything with TE or left right balance. I really don’t even look at power while I am riding. I just like the readiness/fatigue/recovery type stuff. I think that helps me the most for improving.

    4iii has deals now and then also. I got 2 of my new factory installed power meters for 270$ each. That is hard to beat.

    • Duel: Single v Dual

      I don’t think Ray was suggesting single-sided PMs are king, but rather than certain features of dual-sided PMs aren’t a big deal. After all, dual-sided actually measure your total power, whereas single-sided estimate it — and get it wrong unless you are actually 50-50 at all times. This isn’t to say that most of us aren’t close enough to 50-50 to make the single-sided option acceptable, of course.

  10. Richard Mercer

    I put my order in this morning to upgrade my Precision 3 single-side to 3+ Pro before I even saw this review. I’m glad I did now, it’s just a shame I need to ship it off to Canada from the UK. :(

  11. Nate C

    A few years back, Keith Wakeham did a YouTube video where he demonstrated why Shimano’s asymmetric cranksets could never produce accurate right-sided power, and power meters produced on the cranksets (Stages, 4iiii, Pioneer, etc.) would always suffer from this design.

    Perhaps I missed it- did Shimano re-design the newest cranks to address this issue, or are PM companies still trying to to do math that hides the fundamental design flaw, and could that account for the variable inaccuracies you found in your analysis that you couldn’t explain?

    (I ask this as someone who owns two of the cranksets affected in the original reports, a Stages dual r8000 and a Pioneer dual built on r6800… Both affected by the Shimano crank recall where I have to wait until they break mid-ride and cause injuries because the recall doesn’t provide for removal and reinstallation of the PMs?)

    • The Real Bob

      The recall provides 500$ to replace your power meter. I know, I had the giant (pioneer I believe) dual sided power meter ultegra carnk. Turned in. Got a new crank and 500$. I just added the 4iii single sided power to it.

      You don’t have to wait until the crank breaks. Mine had no signs of breaking but they took it back.

    • Nate C

      I found the video, not sure if it will let me post the link here, but very interesting analysis from one of the forefathers of PM development (who I believe worked or consulted for 4iiii at one time?)…

      link to youtu.be

    • Nate C

      Thanks, The Real Bob! I will look back into the recall replacement stuff. Would be nice if I could get a new dual sided PM installed on the replacement cranks for 500-600 so I’m not out a bunch of money to get the same functionality, or maybe, if the Shimano crank design flaw still exists, take the $500 towards some more pairs of pedal-based PM (my pair of assiomas was about 550 when I purchased them, and I passed on the opportunity to purchase wahoo speedplay dual for about that price a year ago).

  12. Frozen

    Thanks for the review! I’ve yet to see any reviews online for the SRAM X0 Eagle AXS Transmission Powermeter. At $400 for the complete power meter crankset with rings it’s insanely cheap. I’m curious as to the accuracy and how it stacks up against stages and other one-sided PM’s. I know MTB isn’t really your jam, but this one has really piqued my interest.

  13. Pete

    I have mixed feelings about 4iiii as a company. I have the previous model (can’t keep track of terminology). No concerns with data or functionality. I was tempted by the deal to upgrade and add findmy capability for $29. It seemed more elegant than my current AirTag solution. And for the cost of an AirTag would free up an AirTag to use elsewhere – essentially free. The shipping and return details may be hidden somewhere in their FAQs but not on the product page. Shipping upgraded unit to me was $10 – not unreasonable. Sending my old unit to them from PA was ~$60 – nowhere on the product page did it remind me that 4iiii was in Canada. For total cost, I could have got 5 new AirTags. I feel a little bait and switched. But at least my bottle cage will be 5mm closer to my down tube…

  14. Laurens

    The operational temperature range is interesting and odd. Surprised this is not on your radar. The lowest point is zero degrees Celsius which means you can’t trust it in the winter, high altitude mountain passes, or after rainy spring downhills.

  15. David Tang

    Two suggestions for 4iiii:

    The Android tracking option needed to be with Tile to be meaningful in North America. You need enough subscribers for the network to work meaningfully.

    And your suggestion of Poutine for a name can be improved. For tracking designation, if 4iiii only provides Apple Findme tracking, then a Canadian varietal of Apple should be in the name. Say Ambrosia or Spartan, McIntosh or Artic Apple, perhaps combined with Maple Pie. So Maple Spartan Apple Pie or something like that. Or even just Pie. Or Crumble, or Crisp or Turnover. Apple Turnover for dual sided and Apple Pie for single would make sense. No charge from me either. I would actually but one for sure with that name change (4iiii I am happy to send my cranks in for factory option). Dave

  16. Stefan Trost

    Hi Ray! perfect review and thanks as my SL8 came with this PM delivered :).

    I’m asking myself how to connect to Zwift via BT? What side of the PM I should connect to Zwift for control of the power…

    thx keep on going,

  17. Pavel Stanek

    Very good review as usual. You might consider to test Inpeak. I had Stages and 4iiii and both after sometime were reading nonsense numbers while Inpeak on MTB still working fine(and never had nonsense peaks, too). So I am considering their dual PM on road bike.

  18. Randall

    What’s the deal with power meters for Shimano 105 di2?

    No single sided or double sided units from 4iiii or Stages even though it’s been out for nearly a year and half.

  19. powermeteruser

    “Apple’s FindMy integration built-in (which you can now share an object’s location with friends/family, effectively allowing them to track your rides easily)”

    This is not entirely correct – the Find My integration only works when the power meter is not in use. So maybe if you make some stops on your ride it will update the location but it does not sound like it will be constantly tracking your location.

    From 4iii’s own documentation:
    “While the power meter is not in use, Find My is enabled and allows you to see its location on a map.”

  20. Tom Roaf

    Am I correct in seeing a correlation between your opinion on a device and how you sign-off the introduction section? It is seemingly either “as always I will return the media loan unit” or the same but with a supplementary statement “and go out and buy my own”. I always assume if you don’t say you will buy your own that you don’t like it/don’t see a good value proposition or am I over analyzing?

    • No particular alignment between that and whether or not I think the device is worth getting.

      Generally speaking, I go out and re-purchase devices when I think there’s significant interest in future firmware updates to cover in future posts/videos, or for future comparison videos. For example, some mid to high-end trainers, most Garmin/Suunto/Apple/Polar/COROS/Samsung/Google/Fitbit/etc watches, plus most action cams and drones. Obviously, that involves a small ROI calculation on my side, to figure out if the cost of $500-$1,000 device can be recouped in future update posts/videos.

      Whereas crankarm based power meters, less so. There really isn’t much demand there for followups, especially if it sticks the landing the first time around. Otherwise these things just pile up around the DCR Studio. Heck, even trainers just pile up in the trainer graveyard. Trying to do less repurchasing everything if there’s little demand for further follow-up content on it.

  21. Matthew


    I was watching GPLama’s Digital Peloton from a few days ago – link to youtube.com – and in the section on this power meter he mentioned he’s seeing “weird” (my word) zero offset issues in some circumstances. Did you see these as well? Have you and GPLama talked through these? Do these change your review in anyway / raise any concerns?

  22. Dean


    I’m in the market for a power meter for my TCR with Ultegra 8100 12 speed, 36/52 rings. Garmin Edge 540 head unit.

    If this were your decision would you choose:

    1: The 4iiii Precision 3+ Pro in this article

    2: The NGeco Rotor ALDHU-R 24 power meter

    3: QUARQ DFOUR DUB (would also require a new bottom bracket ~$40)

    4: other option?

    Options 2 and 3 don’t look great with the 8100 chainrings but I could live with that if either are the best choice.


  23. Mathieu valotaire

    Poutine power meter. Although I love it, that’s more french canadian specific, was funny though

  24. I’m currently testing a 4iiii Precision 3+ (dual sided Ultegra version). What’s disappointing is that i can’t actually find a way to access the frequency response of the unit, like i can with an SRM, Infocrank, Power Tap, P2M, etc so that I can do a static calibration of the unit.

    It’s all well and good doing a comparison to another power meter (I’m trying to compare to my Tacx/Garmin Neo2) and the issue is that i’m unable to ascertain which meter is incorrect as there’s divergence between the two.

    Having a frequency response in the app so you can see the actual torque when you apply a known mass to the meter would make it more useful. I understand that not many people are going to do this, but surely it’s important for data scientists, coaches, etc.

    Do you know of a way to ascertain the actual torque for a static calibration, Ray?

  25. Steve Esmacher

    Sharing my recent (Feb-Apr 2024) experience with 4iiii.

    The what:
    – 4iiii Power Meter, 2 sided, Factory Install.
    – This is my third (4-18-24) power meter from 4iiii – My second factory install, My first 2-sided, My first Precision 3+

    The good:
    – Competitively priced.
    – Now that the 2-sided Precision 3+ power meter is working all seems fine.

    The bad:
    – Shipped my crankarm to 4iiii on February 20 and received it back on March 18. Twenty working days end-to-end (including shipping from/to USA). Slow but reasonable.
    – When first received my crankarm back, the non-drive side power meter wouldn’t pair and the Find My feature wouldn’t work either.
    – Contacted 4iiii support and followed recommended actions. Still wouldn’t pair.
    – Shipped my failed 4iiii power meter/crankarm back on March 22.
    – Received a working 4iiii power meter on April 17. Nineteen working days end-to-end. Slow and unreasonable considering 4iiii was correcting THEIR problem.
    – In calendar days (which is more important to actually being able to ride my bike) it took 58 days. It took 46 emails to get various things resolved over the course of this time.
    – The 4iiii status system is relatively useless because the most important step “Work scheduled or underway” doesn’t have sufficient resolution for one to actually be able to tell what’s going on. The status stays at that high level point for upwards of 8 business days.
    – I was told I would receive a tracking notice each time 4iiii shipped my power meter/crankarm(s) back. This didn’t happen either time. They just arrived – surprise!

    Overall impression:
    – 4iiii has some improving to do in their business, quality control/assurance, status, support, corrective action and communications processes. This is not rocket science folks.
    – If ordering factory install from 4iiii be prepared for some frustration.
    – If “Michael” is the person who replies to your initial support request, ask for someone else. He seems disconnected from the factory install process (snippy, defensive, provided incorrect status, unable to accelerate the corrective actions for what was a 4iiii failure, non/slow response).
    – Once it was determined that 4iiii had shipped me a bad power meter it would have been nice if they had actually apologized. It would have been even nicer if they had moved their defective power meter up to the front of the Factory Install line to correct their/my problem more quickly. Michael did neither.

  26. Andrew B

    I posted a couple times here about my Stages Ultegra 8100 LR.

    The short version is that I have been through 3 in the space of 6 months. In each case R side became a random number generator.

    The store kindly replaced the first two, and will refund the third. I suspect all three may have been from same batch (large national retailer etc).

    I am now torn between the 4iiii version and the Garmin pedals. For various reasons the pedals will be around £150/$200 cheaper for me.

    Despite the above good review- and positive feedback from Ray on his Stages experience- I wonder about the Shimano R crank issue being properly resolved

    For me, all signs pointing to Garmin- although if anyone has an alternative view, I would love to hear.

  27. Marco

    Can the left only power meter be installed on any Shimano crankset? I have an old ultegra 6750 and was wondering if I could just purchased the left arm PM and it would fit without issues.

  28. Thomas I

    Great review, as usual… I have to share my recent poor experience with 4iiii. Unfortunately, their service has deteriorated significantly over the years. It seems they are only concerned with their corporate buyers. My first 4iiii power meter was purchased in 2016. The turnaround time was 12 days from when I sent my crank until I received it at home. I ordered another in 2022 when the previous one malfunctioned and gave outrageous power readings during 2021. Out of warranty, they were nice enough to provide a discount on the replacement. It took 12 days from when I sent my crank in until I received it. My power meter died last year. Completely dead. After troubleshooting with 4iiii, I was asked to send my crank in for a warranty replacement. It was 2 Months before I saw my crank again. 2 MONTHS! And their so-called customer service rep, Michael, stopped answering my emails after the first month. No response, nothing. I will never deal with them again and recommend anyone stay far away. There are other reputable companies with quality products.

  29. Tim


  30. coolsurfing

    @DC Rainmaker,

    Did you test it under rain conditions ?
    Thanks fgor your help !

  31. Candace Carlisle

    I’ve watched their video, and looked at their graphic, but I still can’t figure out how to remove the battery on the newfangled 4iiii with the clip. *Nothing* will budge. Anyone?
    link to 4iiii.zendesk.com

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  33. Tom Nilsson


    I’ve been eyeing a 4IIII power meter for the non drive side, but cannot seem to find the exact measurements of the width of the inside of the crank to determine whether the distance between the bottom tube/bottom bracket and the pod of the power meter cap to be wide enough.

    Do i understand correctly that the “profile” section in the above comparison of 5.5mm vs 7.5mm concerns this distance? Compared to the older models, that would only be a 2mm reduction of the pod?

    Thank you.

    • Thomas I.

      Generally, if you can fit a AA battery between crank arm and frame, the power meter will fit. I would highly recommend getting another pm though given 4iiii recent poor customer service. I returned my crank arm for a warranty replacement earlier this year and it took a full 2 months before they returned it. 2 months for a replacement they said would take 2 weeks. No response to emails after the first month. Very unprofessional. At least one other commenter had a similar experience. It’s good value when it works, but you might regret it when it eventually fails.