4iiii manufactures the PRECISION and PRECISION PRO power meters. The PRECISION PRO (pictured below) takes the original single-sided PRECISION to the next level with dual-sided power. The PRECISION PRO locates a power sensor on both the left crank arm as well as the chainring, allowing you to measure both left and right leg power independently. The PRECISION PRO comes pre-installed on a Shimano DURA-ACE 9000 series crankset.
In addition to being affordable, lightweight and highly accurate, the 4iiii PRECISION PRO measures precise cadence data, have 3D power meter technology capable of measuring tri-axial strain and are compatible with both ANT+ and Bluetooth SMART devices.
Installation of the PRECISION PRO requires you to remove your current crankset in it’s entirety and install the PRECISION PRO in its place. However assuming you have insured compatibility with your bike frame – it’s pretty straightforward.
The PRECISION PRO ads a mere 20 grams to your crank – making it the lightest power meter you can buy.
Left/Right Power Measurement
The PRECISION PRO measures left/right power. The PRO locates a power sensor on both the left crank arm as well as the chainring, allowing you to measure both left and right leg power independently.
The PRECISION PRO uses two CR2032 batteries – one in each sensor. We like CR2032 batteries as they are cheap and very easy to find. Note that batteries are provided with the power meter.
Battery life is right around the 100-hour mark. When you have 15% battery power remaining, you will receive a low-battery alert on your head unit. This is a nice touch and serves as a reminder to replace your battery soon.
Difficulty to Change
Easy. The battery in the left side crank arm is changed by hand – no tools necessary. The battery for the sensor that is mounted on the chainring is replaced by unscrewing the three small 1.5 mm bolts that are located on the outside of the sensor cover. (A 1.5 mm hex key is provided with the power meter so you don’t have to worry about sourcing one.) Both batteries can be changed in under five minutes.
The PRECISION PRO transmits data via both the ANT+ and Bluetooth SMART wireless protocols. This means they are compatible with any bicycle computer, smart phone or tablet.
The power meters are accurate to within +/-1%. This is on par (to slightly better) than the majority of other power meters on the market.
Like most power meters, the PRECISION PRO uses an accelerometer to measure cadence. An accelerometer is an electronic device that is housed inside the power sensor and measures your pedaling rate.
The PRECISION PRO should be calibrated before ever ride – which is standard procedure for power meters. Calibration only takes 30 seconds and is performed using your bicycle computer.
The PRECISION PRO comes with a one year warranty which covers the product from defects in material and workmanship.
4iiii offers an app for both iOS and Android devices, allowing you to connect your smart phone or tablet to your power meter using Bluetooth. You can use the app to update the firmware on your power meter and to perform pre-ride calibrations (zero-offsets). In addition, the app offers training metrics so you can use it as your primary or secondary head unit.