Product Review : Maximize Your Cycling with 4iiii (Foureye) Power Meters – Precision 3+ Review

Power for Zwift or for outside 4iiii has you covered

So, you decided you need to know how many watts you are creating, that’s a good thing. More data, more intelligence, right. In the past I have used power measurement to help in training for racing. but more so today I use power to be able to ride with fiends virtually and also to gauge my efforts over the summer months. 4iiii is an established sensor company that offer cost effective power meters that are easy to install and of high precision. Generally only the highest level bikes come off the shelf with some type of Power meter included. 90% of Power meters get added through bicycle upgrades. Manufacturers like SRAM and Shimano have options where power measurements are built into and made at the crank / chainset, SRAM offer a range of their cranks / chainsets from Rival, Force and Red. all of which have models that measure power. Shimano on the other hand offer it on their highest end only DuraAce and rely on third party companies to provide a range of upgrade options from companies like 4iiii

What are the unique features of a 4iiii power meter?

• The Precision 3 has numerous sensors, an accelerometer and a gyroscope, it’s precision is rated at + /- 1% which is quite good compared to many at + /- 1.5 or 2%. This range may sound too precise but for example plus or minus 1% at 300Watts is 6 watts, so your power reading could be 294 or 306w. if your power meter was plus or minus 2% that would be a swing of 12watts!
• The Precision 3 has a “+” version, this version includes Apples Find My technology, so you can always keep an eye on the location of your bike via your phone.
• The Precision 3 uses a standard coin cell battery, no recharging, the catch her, it lasts 800hrs, thats pretty much two years of someone who rides a lot.
• 4iiii allow you to send your current component craink / chainset to their factory to have a power sensor added, this reduces your cost.
• 4iiii offer a standard 3 year warranty, much better than the normal 12months offered with many, 2years offered by SRAM

What’s the cost of a power meter?

When taking the path of upgrading components generally you can expect to pay extra to add power measurement, options run a large gaumet from $350 to over $1000 depending on which parts and levels of gear you are replacing or adding to. If replacing crank /chainset manufacturers like Sram will have a few options, A Sram Force version with power will cost around $850 and a non power one will be around $450. But there is another option which 4iiii excels at…. solutions start from $339 adding to what you already have.

Which drivetrains / chainsets will the 4iiii work on?

4iiii offer upgrades across both big the brand Sram and Shimano, plus more unique offerings like Cannondale, FSA and TRP. You can buy a brand new ready to ride part (thats what I did) or they have a service where you can have a new power sensor bonded to a crank / chainset you already own by sending them your gear. (For the more unique manufacturers you may have to send your part to them)

4iii Product Choices and Options

Then theres a couple of product options, that are mainly driven by your budget. A single sided power sensor which will measure power from just your non drive side or you can go with what they call the Dual sided.
Dual Sided means there are sensors in the left and the right, this is generally more expensive but will show you any power discrepancies between sides and it will show you pedaling dynamics – (peal smoothness and torque effectiveness) for both left and right.
Single Sided are the less costly option and will measure power from the non drive side. For most people single sided is a good choice and has a lot of benefit. Single sided is a little quicker to install also since you don’t have to remove the whole crank / chainset

For either ~$980 (new part) or $549 (retrofit) you can have dual sided power measurement. (The retrofit dual side version requires you to remove your crank from your bike and send to the 4iiii factory for them to bond a power sensor on)

How?

OK, so how do we do this? Firstly theres a check, a check to make sure the sensor will fit, and that you have enough clearance on your bike. The power sensor electronics are housed in a little plastic bump, and some carbon bikes do not have a lot of space between crank arm and frame, so you will want to do this check before buying. On the 4iiii website you down load a pdf, print and align on your bike, it’s very easy to check. You can see on the image below that I have a lot of space on my metal frame.

Ordering is easy and shipping is super fast, mine took 3 days. For installation you will need a few basic tools dependent on your crank Brand. Here are tools shown for Shimano. For Sram you will need a bigger torque wrench. Installation pictures are below.

Technical Specs

The specs on a 4iiii are very good, great battery life, durable, 3 year warranty and accurate product. More details here https://us.4iiii.com/tags/power-meters/#comparison

4iiii Specifications
Accuracy	1 % accuracy
Electrical Power	Coin cell – battery Powered
Battery Life	800hrs single sided, 700 Dual Sided
Max Power	up to 4000watts
Durability	IPX7 waterproofing – Withstands incidental exposure to water of up to 1 meter for up to 30 minutes.
Communication	Ant+ and Bluetooth, most headunits.
	Apple “Find My”

In Use

I purchased a single sided Ultegra setup, The installation was a breeze, my setup was Shimano and it was a simple non drive crank arm swap. I removed the pedal, unbolted the crank arm, applied a little grease and torqued the new one on. Please note Shimano pinch bolts are 12-14Nm ). I think this is a little easier than the Sram equivalent, since the torque settings are much higher, thus requiring more elbow grease!
The electronic setup was fast and easy by downloading an app and pairing the device. The App allows you to update firmware and to also calibrate.
Pairing the sensor to the headunit was a snap, in this case a Wahoo Roam 2, found the sensor within a few seconds and automatically added power and cadence readouts to the screen’s data fields.

Calibration – 4iiii recommend that you calibrate before each ride, this sounds like a pain in the arse, but in reality it wasn’t, as the process literally takes 3 seconds and you can do it from your cycling headunit or the app on your phone.

The startup speed is incredible, no messing around. spin the crank to wake it and your headunit finds it instantly, no waiting.

Recommendation

If you want the easiest and most cost effective option into power, you will want to go Single Sided which can be purchased from $339, this technology uses a strain sensor on the non drive crank / chainset arm to measure power. This is as simple as a 15 minute job, bolting on a new non drive side crank arm.

If you are very much into squeezing the last drop of info, then the Dual Sided would be the way to go as it provides more cycling dynamics and specifically can call out L vs R. The best method for this would be to send 4iii your crankset as this ultimately will be the most cost effective way.

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Install Pictures (Shimano Setup)

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