4iiii PRECISION Shimano Ultegra R8000 Power Meter
May 23, 2023$334.99 – $384.99
4iiii’s PRECISION power meter combined with Shimano’s Ultegra R8000 groupset
4iiii PRECISION Shimano Ultegra R8000 Power Meter
Introducing the all new 4iiii PRECISION Shimano Ultegra R8000 Power Meter. 4iiii has combined their patent pending 3-D tri-axial strain gauge technology, measured at +/- 1.0% accuracy, with Shimano’s best of breed Ultegra R8000 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 R8000 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 R8000 PRECISION 3!
The all new 4iiii R8000 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 (PRECISION 3), 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
- Versions: PRECISION 2 | PRECISION 3 (see above for PRECISION 3 differences)
- Crank arm lengths: 165 mm | 170 mm | 172.5 mm | 175 mm
Other Versions to Consider
Dual-Sided R8000 Crankset: We also sell the 4iiii PRECISION PRO Shimano Ultegra R8000 Dual-Sided Crankset which is a complete crankset. It is more expensive, however it measures power from both legs.
Compatibility
Crankset: This 4iiii power meter is compatible with Shimano R8000 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 10 mm of clearance for the PRECISION 2 and 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 R8000 Specs
| Name | 4iiii PRECISION Ultegra R8000 |
| 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 | Version 2: 100 hours / Version 3: 800 hours |
| Method of Cadence Measurement | Accelerometer |
| Warranty | 3 years |
In the Box
- 4iiii PRECISION Shimano Ultegra R8000 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:Â What is the difference between the 4iiii PRECISION 2 and PRECISION 3?
- The P3 was introduced in early 2022 and offers several benefits over the P2 model. Please see our article for more information: 4iiii PRECISION 2 vs. PRECISION 3 Comparison.
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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joel mclarry (verified owner) –
Power meter works great with wahoo bolt. No issues, power drops or spikes. Very easy install that took 5 minutes.
Power Meter City –
Hi Joel. Thanks for leaving a great review on your 4iiii PRECISION Shimano Ultegra R8000 Power Meter. We hope you continue to enjoy them and we are here if there is anything else we can do!
Chuck P (verified owner) –
Doing a new build and since I have a 4iiii Precision power meter on my other bike (b-day present last year) that has been flawless, why fix what ain’t broke? Very fast shipping from Power Meter City. Easy peasy installation and pairing to my head unit (Wahoo ROAM with associated iPhone app). The only learning curve was figuring out you can’t pair two power meters at the same time on the 4iiii app. Minor inconvenience, but not a big deal. But it does mean having to unpair one power meter and re-pair the other whenever I switch riding bikes. Otherwise, the 4iiii Precision power meter works as advertised, i.e., it tells me how much I suck. 🙂
Power Meter City –
Hi Chuck. Thanks for this! Good choice BTW. We hope you continue to enjoy your new 4iiii PRECISION Shimano Ultegra R8000 Power Meter. We are here if there is anything else we can help you with!
Kris J (verified owner) –
This is an excellent power meter. Took 5 minutes to install and link with head unit. That’s it. Works exactly how it should.
Power Meter City –
Wow! Thanks for this Kris. We hope you continue to enjoy your 4iiii power meter and we are here if there is anything else we can do!
jpipkens (verified owner) –
First to the credit of Power Meter City; ordering was easy. I ordered on 8/3/20, it shipped on the 4th and was in my mailbox on the 7th! After pouring over reviews of Stages vs 4iiii I decided to go with this PM. The packaging and product itself are top notch, like opening an Apple iPhone. Installation was easy and took just minutes. No issues here with the app or connectivity. Everything synced well with my Wahoo Elemnt Roam. Calibration is easy and initiates right from my Wahoo computer. Just make sure the bike is perfectly still and the cranks are perfectly vertical. My biggest concern was accuracy so I ran multiple comparisons. One was the crank PM paired with my Wahoo Roam. The other was my Wahoo Kickr controlled by and paired with Zwift in ERG mode. I put all of the .fit files into DCR Analyzer and was pleased with the result. The power output of the crank is very spiky and of course cannot show left/right leg imbalances, but thus is the nature of left sided PMs. Across the entire plot though the averages matched up and I did not see any drift over time. Satisfied with that I began playing with the zero offset from the 4iiii app, which does work nicely in either direction, and luckily for me the zero setting on mine was the closest match to my Kickr’s output. All in all I could not be happier with the purchase and the product itself. I love using the metrics of power to pace and push my indoor training and now I’ve found a reliable way to take it on the road! Buy it and enjoy!
Power Meter City –
HI jpipkens. Nice job! Wow! We are glad you are enjoying your 4iiii PRECISION Shimano Ultegra R8000 Power Meter. Good luck on your future rides – we hope you continue to enjoy them and please let us know if there is anything else we can do!
Dennis Gately –
Receiving the crank arm with power meter in just 3 days was astonishing considering shipping & deliveries during the coronavirus. The crank arm was easy to install and I got the power meter up & running quickly. Pairing to my Garmin 820 took very little effort and I am now enjoying having my power data on display whenever I ride. Thanks ???? 4iiii & Power Meter City!
Power Meter City –
Hi Dennis. We are glad it worked perfectly as expected. Good luck on your future rides! We hope you continue to enjoy them and please let us know if there is anything else we can do!
Aaron Braswell –
Simple, fast, and awesome! Works great. Thanks for making it easy!
Power Meter City –
Hi Aaron. Thanks for this kind review. We are glad it worked great as expected! Please let us know if there is anything else we can do!
Marc Saunders (verified owner) –
Power meter was simple to install and configure on Garmin and Zwift, and delivery to a small island in the Atlantic was speedy!!
Power Meter City –
Hi Marc, we are glad you got your 4iiii PRECISION Shimano Ultegra R8000 Power Meter on time. We hope you continue to enjoy it! Please let us know if there is anything else we can do!
Luke Caldwell (verified owner) –
Power meter works great and it was cheaper than what I saw other places online. Customer service was top as well. They even called to make sure I had selected the correct one and had it shipped out same day.
Power Meter City –
Hi Luke. Thank you for leaving this great review on your 4iiii PRECISION Shimano R8000. We appreciate your business with us and we are here if there is anything else we can do!
Dayle James (verified owner) –
Couldn’t have been easier to sync with my wahoo and get on the road! Based on my experience with other power meters, this has been very accurate, great battery life, and handles well in weather. Now it’s on me to get my FTP up! Already looking at other 4iiii for my other bikes!
Power Meter City –
Hi there Dayle! Good choice for your power meter! We hope you continue to enjoy them and Yes, please let us know if there is anything else we can do!
John kneebee (verified owner) –
I’ve been using the 4iiii precision r8000 for about a month now and have logged 2k Mike’s with it. It has been flawless! I did several comparisons to its power numbers benchmarking against my wahoo kickr and it has been +/- about 2 or 3 watts which for a single sided unit for $350 is great to me. Also it is very easy to install and to calibrate. If I had to say one criticism it’s that it would be nice if it had an auto zero feature because sometimes I have forgotten to do the zero offset calibration pre ride. Other than that it’s great I would highly reccomend also side note shipping was very fast 2 days which was awesome!
Power Meter City –
Hi John. Thanks for this awesome review! Keep up the good work! We hope you continue to enjoy them and we are here if there is anything else we can do!