4iiii Ultegra R8100 Precision 3+ Power Meter

The 4iiii Ultegra 8100 Precision 3+ is the successor to the Ultegra Precision 3. The Precision 3+ has some new features, including support for the 'Apple Find My' app. This allows you to accurately see the location of the power meter via the app when you are not using it. So you know where your powermeter is at all times!

New features
Support for 'Apple Find My' allows you to see the location of your powermeter with an Apple smartphone, iPad, Mac or Apple Watch. Simply add the power meter to the app. Furthermore, the new feature 'Automatic Terrain Selector' has been added, which can detect different types of terrain. The powermeter then automatically switches between different methods to measure cadence, accurately measuring your delivered power on any terrain!

Exact measurement
The Precision 3+ powermeter gives a very precise measurement with a deviation of only 1%. The force you deliver will cause the crank to flex and rotate in all 3 dimensions. To ensure that every force you apply to your pedal is measured in every dimension, 4iiii has developed the 3D power measurement system. This measurement system measures multidimensional load, so you can be confident that your unique pedal stroke will still be accurately measured regardless of your riding conditions.

Single-sided power meter
The 4iiii R8100 power meter measures the power on the left crank and double counts it to give you a total power across both legs. For most riders without limitations, the power on the left and right leg is almost the same for even efforts. Furthermore, your cadence is measured as standard.

Light
Due to its very lightweight design, the sensor adds only 9 grams to a standard Shimano crank. This makes it the lightest powermeter on the market!

Battery life
The 4iiii Precision 3+ does not have an internal battery, but uses button cell batteries. The downside of this is that you do have to replace them from time to time. Fortunately, the battery lasts more than 800 hours, which is a lot longer than most internal batteries in powermeters and its predecessor. If the battery is below 15% you will get a notification in the 4iiii Device Configuration. So you are always on time with replacing your battery.

Connectivity
Calibration is done via 4iiii Device Configuration. This app is available for Android and iOS. Through this app, you can also see the state of the CR2032 button cell battery. This power meter transmits both an ANT+ and a Bluetooth signal. This makes this power meter compatible with almost all bike computers. If you are not sure if your bike computer or sports watch is compatible, you can look up in the user manual of your bike computer whether it is compatible with ANT+ or Bluetooth and with power measurement.

• Weight: 9 grams
• Connection: ANT+, Bluetooth
• Measurement deviation: ±1%
• Power supply: CR2032 (up to 800 hours)
• 3-year warranty
• Water resistance rating: IPX7
• Active temperature compensation
• Power range: 0-4000W
• Cadence range: 30-170RPM

• This crank arm obviously fits an Ultegra R8100 crankset, but also fits other Hollowtech II race cranksets.

Note: The 4iiii Precision powermeter is slightly wider than a Shimano left crankarm due to the powermeter unit. This may cause problems with some bike frames. To determine if your frame is compatible, you can perform a test. To do this, you need to be able to move an 8 mm Allen key vertically between your crank arm and chainstay. There is a picture on the last product picture of this page to clarify it. Optionally, 4iiii website also has a handy little document you can print out and stick on your crank. Then you will know exactly between which points the 8 mm Allen key should be able to move. When there is enough space for the 8 mm hex key, you can assume that the 4iiii powermeter is compatible with your frame!

- 1x 4iiii Precision 3+ Ultegra R8100
- 1x CR2032 button cell battery

To mount this 4iiii powermeter, you must first disassemble your current left crankarm. Fitting the 4iiii powermeter is exactly the same as fitting a Shimano left crankarm.

1. Remove the pedal on the left side.
2. Loosen the two crank bolts at the top of the crank arm and remove the locking pin from the slot.
3. Next, remove the crank nut with this crank wrench.
4. Now the crank arm is basically loose and you can take it off the axle. You may well have to apply considerable force here. The most important thing is not to damage the crank arm.
5. Then fit the powermeter crankarm by following the steps above in reverse order.
6. Next, do not forget to mount your pedal to the new crank arm and you are ready to ride!

How do I know if my bike is suitable for this powermeter?
First of all, it is important that you have a Shimano road bike crankset. If you don't have one, you will unfortunately not be able to use this powermeter. That means that with a Cannondale bike, you unfortunately cannot use this powermeter. Other cranksets you cannot use are e.g. FSA, SRAM, Praxis and Hollowgram. You can also not use this powermeter on Shimano MTB cranksets due to a different design.

However, you can combine this powermeter with cranksets of an older generation. This can also safely be an older generation than the current groupsets. As long as the mounting method of the crank arm: the two nuts that keep the crank arm in place, is the same. You may then notice an external difference. Below are some cranksets that should fit in any case, provided you have enough space on your frame.
105 R7000, Ultegra R8000 and Dura-Ace R9100

Furthermore, it is important that you have enough space at the swingarm. If you do not have enough space here then this powermeter will not fit. Unfortunately, there is also no way to make the powermeter fit anyway. The best way is to check this with the model from 4iiii.

How can I determine what crank length I need?
Crank length refers to the length of the crank arm and is measured from the centre of the bottom bracket to the centre of the pedal axle. Bikes are basically delivered with the correct crank arm length for the corresponding body height. The length is indicated on the inside of your crank arm in most cases. If not, you can measure it yourself. It is important that the crank arm powermeter you buy is the same length as your current crank arms.

With which software and/or hardware is this power meter compatible?
This power meter transmits both an ANT+ and a Bluetooth signal. This makes this power meter compatible with most current bike computers. Only not all bike computers are suitable for use with a power meter. For this, you will have to consult the specifications of your bike computer. In any case, the common models from Garmin and Wahoo can almost all be connected. The Garmin Edge Explore cannot be paired with a power meter.

Should you not have a bike computer right now, you can also use the 4iiii app to keep track of your workout power data.

How do I calibrate this powermeter?
Calibrating your powermeter is very important for accurately measuring your power output. Make sure no weight is applied to the pedals, and that your right crank is up and your left crank is down (positioned vertically). Rotate the powermeter several times so that it is on. Then, via the 4iiii app, you can easily calibrate your powermeter. Another possibility is to calibrate your powermeter via your bike computer. Most bike computers have this option, check the manual of your bike computer how to do this exactly.