4iiii PRECISION 3 Shimano Ultegra R8100 Power Meter
May 21, 2023$434.99
4iiii’s PRECISION 3 power meter combined with Shimano’s 12-Speed Ultegra R8100 groupset
4iiii PRECISION 3 Shimano Ultegra R8100 Power Meter
Introducing the all new 4iiii PRECISION 3 Shimano Ultegra R8100 Power Meter. 4iiii has combined their patent pending 3-D tri-axial strain gauge technology, measured at +/- 1.0% accuracy, with Shimano’s 12-speed Ultegra R8100 groupset. The result is one of the lightest, most affordable and most accurate direct force power meters available.
The PRECISION determines your total power based on the force that is generated by your left leg. This left-only design allows for a power meter that is lightweight and easy to install. Specifically, the power meter adds only 9 grams to your crank arm and is installed in about 10 minutes. In addition, the PRECISION is compatible with both ANT+ and Bluetooth SMART devices. This means you can use it with your favorite bicycle computer, watch or smart phone.
Key Product Details
Compatibility:
This power meter is compatible with Shimano R8100 cranksets. It can also be installed on other Shimano road cranksets, as long as they use Shimano’s Hollowtech II interface. See Compatibility tab for more information.
Power Measurement:
This 4iiii power meter measures left leg power and doubles the value to account for both legs (assumes both legs are generating the same force).
New 4iiii R8100 PRECISION 3!
The all new 4iiii R8100 PRECISION 3 power meter features the following improvements over the version 2:
- 800 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:
Affordable, accurate to within +/- 1.0%, lightweight at only 9 grams of added weight, 800 hours of battery life, CR2032 user-replaceable battery, ANT+ and Bluetooth compatible, easy to install, 3-year warranty. See Specs tab for more information.
Advice From Our Staff:
4iiii left side crank arms are some of our best-selling units. They work with most Shimano cranksets, are affordable and easy to install. The one consideration is they only measure left leg power compared to some other power meters that measure power from both legs (those versions usually cost more however).
Options For This Power Meter
Crank arm lengths: 165 mm | 170 mm | 172.5 mm | 175 mm
Other Versions to Consider
Dual-Sided R8100 Crankset: We also sell the 4iiii PRECISION PRO Shimano Ultegra R1000 Dual-Sided Crankset which is a complete crankset. It is more expensive, however it measures power from both legs.
4iiii PRECISION R8100 Compatibility
Crankset: This 4iiii power meter is compatible with Shimano R8100 cranksets.
Please note, the power meter can also be installed other Shimano road cranksets, as long as they use Shimano's Hollowtech II interface. These cranksets can easily be identified by the two opposing pinch bolts that are used to secure the left side crank arm. Please see the image below and contact us if you have any questions on compatibility.
Check Frame Clearance: Crank-arm based power meters 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 8 mm of clearance for the PRECISION 3. Also, make sure 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 your clearance is close but not quite sufficient, what many people will do is simply install a 1 or 2 mm bottom bracket spacer (between the left crank arm and the frame). This should provide you with the clearance you need.
4iiii PRECISION Shimano Ultegra R8100 Specs
| Name | 4iiii PRECISION Ultegra R8100 |
| Bike Type | Road |
| Location of Power Measurement | Crank Arm |
| Left or Both Legs Measured | Left only |
| Independent Left/Right Measurement | No |
| Installation | Easier |
| Crank Arm Material | Aluminum |
| Communication Protocol | ANT+ and Bluetooth SMART |
| Claimed Accuracy | +/- 1.0% |
| Automatic Temp. Compensation | Yes |
| Weight | 9 grams (added weight) |
| Battery Type | CR2032 coin cell |
| Battery Life | 800 hours |
| Method of Cadence Measurement | Accelerometer |
| Warranty | 3 years |
In the Box
- 4iiii PRECISION Shimano Ultegra R8100 Power Meter
- CR2032 coin cell battery
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.
- Shimano Crank Arm Cap Tool
- 5 mm Allen key
Common Questions and Answers
Question: How do I determine what length my current cranks are so I can make sure I get the same size?
- Your crank arm length should be printed or stamped on the inside of the left crank arm, usually near the pedal end.
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