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4iiii PRECISION 3+ PRO Shimano Ultegra R8100 Dual-Sided Crankset
August 21, 2025$979.99
4iiii dual-sided power on a Shimano Ultegra R8100 crankset
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4iiii PRECISION 3+ PRO Shimano Ultegra R8100 Dual-Sided Crankset
The 4iiii PRECISION 3+ PRO Shimano Ultegra R8100 Dual-Sided Crankset combines 4iiii’s 3-D tri-axial strain gauge technology with Shimano’s latest Ultegra R8100 crank. The result is an accurate, lightweight and highly reliable power meter crankset that is accurate to +/- 1.0%.
In addition, this dual-sided 4iiii R8100 power meter crankset features independent left/right power measurement. With a power sensor located on the inside of both crank arms, the power meter can measure power from each leg individually.
The 4iiii is extremely lightweight, adding approximately 20 grams to the Shimano R8100 crankset. It is compatible with both ANT+ and Bluetooth SMART devices, which means you can use it with any bike computer, smart phone or indoor training app. It also comes with a full 3-year warranty.
Key Product Details
Compatibility:
This power meter is compatible with 2×12 road drivetrains and 24 mm Shimano bottom brackets. Most customers that buy it already have a Shimano R8100 crankset on their bike and therefore, it’s an easy swap. However, it can be used on any road bike as long as its 2×12 with a 24 mm bottom bracket. See Compatibility tab for more information.
Power Measurement:
This 4iiii power meter has a power sensor on both crank arms and measures power from both legs. It is also able to measure your left vs. right leg power.
New 4iiii R8100 Dual-Sided PRECISION 3+!
The all new 4iiii R8100 Dual-Sided PRECISION 3+ power meter features the following improvements over the version 2:
- Apple Find My which allows you to always know where your bike is!
- 550 hours of battery life – the longest coin cell battery life in a power meter on the market!
- Sleeker, slimmer profile making most incompatibility issues a thing of the past.
- Stronger antenna for even better connectivity.
- Indicator light for battery life, successful zero-offset and when the unit has been turned on.
Key Features:
Dual-leg power measurement, can measure left vs. right leg power, accurate to within +/- 1.0%, lightweight at only 20 grams of added weight, 550 hours of battery life, CR2032 user-replaceable battery, ANT+ and Bluetooth compatible, 3-year warranty. See Specs tab for more information.
Advice From Our Staff:
This is a great option for customers with a Shimano R8100 drivetrain that want to keep an OEM R8100 crankset on their bike but add power. We also like that fact that this crankset measures power from both legs and has a 3-year warranty, which is longer than most power meters.
Options For This Power Meter
- Chainrings: 50/34 | 52/36
- Crank arm lengths: 165 mm | 170 mm | 172.5 mm | 175 mm
Compatibility
Bottom Bracket: This power meter is compatible with 2x12 road drivetrains and 24 mm Shimano bottom brackets. Most customers that buy it already have a Shimano R8100 crankset on their bike and therefore, it's an easy swap. However, it can be used on any road bike as long as its 2x12 with a 24 mm bottom bracket.
Check Frame Clearance: Crank-arm based power meters like this one attach a sensor on the inside of the left crank arm. On some bikes, there is not enough room between the left crank arm and the chainstay for the sensor to clear the frame. Therefore, you should make sure you have at least 10 mm of clearance between the left crank arm and the chainstay - and that you don't have a bottom bracket mounted rear brake (used on some aero and TT bikes). The important area to measure is right in the middle of the crank arm. Please refer to the image below.
If you find that you have around 7-9 mm of clearance, what many people will do is simply install a 1 or 2 mm bottom bracket spacer (between the left crank arm and the frame), which will give them the clearance they need.
4iiii PRECISION PRO Shimano Ultegra R8100 Specs
| Name | 4iiii PRECISION 3+ PRO R8100 |
| Bike Type | Road |
| Location of Power Measurement | Crank arm |
| Left or Both Legs Measured | Both |
| Independent Left/Right Measurement | Yes |
| Installation | More involved (60 min. estimated) |
| Crank Arm Material | Aluminum |
| Communication Protocol | ANT+ and Bluetooth SMART |
| Claimed Accuracy | +/- 1.0% |
| Active Temperature Compensation | Yes |
| Weight | 736 grams (170 mm, 50-34T) |
| Battery Type | CR2032 |
| Battery Life | 550 hours |
| Method of Cadence Measurement | Accelerometer |
| BCD | 110 4-bolt asymmetric |
| Spindle Size | 24 mm |
| Q Factor | 148 mm |
| Warranty | 3 years |
In the Box
- 4iiii Dual-Sided Power Meter Crankset
- 2 CR2032 coin cell batteries
Tools Needed for Installation
You will need the following tools for installation of this product. You can purchase many of these commonly used tools in our store.
Q&A
Have a question about this? Ask the staff.
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