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4iiii Power Meters

4iiii power meters, available for Shimano road, gravel and MTB cranksets, are some of our best-selling units. This is due to their affordability, ease of installation and accuracy. The company offers left and right side crank arms as well as complete cranksets. With the left or right side crank arm, the user simply swaps their current crank arm out for the power equipped version. With the dual-sided cranksets, the entire crankset is replaced with the new one. These power meters are accurate to within 1.0% and feature ANT+ and Bluetooth SMART. Their new PRECISION 3+ models feature an industry leading 800 hours of battery life.

Additional 4iiii Power Meter Info:


Installation of the 4iiii PRECISION crank arm is very easy. You simply remove your current crank arm and install the 4iiii power meter in its place. Installation time is usually under 5 minutes.

4iiii cranksets take a bit more work as you have to swap out your entire crankset, however assuming you have insured compatibility with your bike frame and bottom bracket – it’s still pretty simple. Installation time here is probably closer to 30 minutes. Please note that for both power meter types, you will need a Shimano preload cap tool to remove the left side crank arm.


4iiii power meters are the lightest power meter available. The PRECISION sensors adds only 9 grams of weight to the crank arm.

Power Measurement

Like other left side power meters, the 4iiii PRECISION left crank arms measure left leg power and double the value to calculate total power. Assuming you don’t have a significant left/right leg imbalance, this is an accurate way to measure power. Complete 4iiii crankset power meters measure both legs. They are therefore able to account for any left/right imbalances. They are also able to determine independent left/right power.

Special Features

Several features stand out regarding 4iiii power meters. To begin with, with models starting at $334, they are one of the most affordable, ready to ride direct force power meters available. They are also extremely lightweight. These power meters add less than 10 grams of weight to your crankset. In addition, the new PRECISION 3+ model features 800 hours of battery life and Apple Find My technology, so you always know where your bike is!


The PRECISION uses a CR2032 battery. The PRECISION 2 gets 100 hours of battery life whereas the PRECISION 3+ gets 800 hours. CR2032 batteries are cheap and easy to find.

Communication Protocol

These power meters transmit data via both the ANT+ and Bluetooth SMART wireless protocols. This means they are compatible with any bicycle computer, smart phone or tablet.


4iiii power meters are accurate to within +/- 1.0%. This is on par (to slightly better) than the majority of other power meters on the market.

Cadence Detection

Like most power meters, the power meter uses an accelerometer to measure cadence. An accelerometer is an electronic device that is housed inside the power sensor and measures your pedaling rate.


4iiii power meters come with a three-year warranty which covers the product from defects in material and workmanship. We note that this is longer than the typical warranty of one to two years.


How does a 4iiii power meter work?

4iiii Innovations attaches a power sensor onto the inside of the crank arms. The power sensor consists of a strain gauge, some electronics and a battery. A strain gauge is a tiny electronic device whose electrical resistance varies depending on how much resistance (strain) is put on them. In the case of a 4iiii crank arm for example, it measures how much your crank arm is flexing when you ride. The power meter converts this flex into a power or torque reading that is sent wirelessly to your handlebar mounted bike computer where you can view your power in real-time.

Will a 4iiii power meter fit my bike?

There are two parts to this question. The first is in regards to crankset compatibility. 4iiii makes Shimano road and MTB power meters so you need to make sure you have a compatible Shimano crankset on your bike. Secondly, you need to make sure your frame can fit a crank-arm based power meter on your bike. This means you need to make sure there is the necessary clearance between the left crank arm and your chainstay. For the PRECISION 2, you need 10 mm of clearance. For the PRECISION 3+ model, you need 7 mm of clearance. You should also confirm that you don’t have a chainstay mounted rear brake, as these often get in the way of the power meter. Please refer to the image below.

Image showing the clearance between the frame and left side power meter crank arm

Are 4iiii power meters accurate?

Yes. 4iiii units are accurate to within +/- 1.0%. The industry average for power meter accuracy is 1.0% to 2.0% so these are considered some of the more accurate power meters.

How long does a 4iiii power meter battery last?

Battery life for the PRECISION 2 is right around the 100-hour mark. The PRECISION 3+ gets 800 hours.

What head units does a 4iiii power meter work with?

You can use the 4iiii power meter with any ANT+ enabled head unit, as well as with a smart phone using Bluetooth SMART.

How do you change the battery on a 4iiii power meter?

You can change the battery on a 4iiii very easy. For left side crank arms, there is a small, round battery door that pops off, exposing the CR2032 battery. For right side crank arms, there is a small door that is removed by unscrewing three small screws. You can change a 4iiii battery in only a couple of minutes.

Does a 4iiii power meter measure speed?

No. A 4iiii power meter measures both power and cadence. Speed is measured by the GPS in your bicycle computer. You can also choose to add a speed sensor to your bike if you would like to.

Please see our 4iiii FAQ for more information on 4iiii power meters.

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