There are three power meter options for a Shimano GRX crankset;
- Left-sided
- Spider-based
- Pedal-based
In this article, we’ll explore these three options in detail.
Left-sided power meters
For left-sided power meters, you can choose between;
- 4iiii Precision 3
- 4iiii Precision
- Stages Power Left
The existing left crankarm will be swapped with a similar left crankarm with a power meter unit. The power meter unit is built onto the left crankarm and weighs 9g (4iiii) and 15g (Stages).
These are only available for GRX810. They’re not available for GRX600 crankarms because the unit cannot be installed on the inner side due to its non-flat surface.
Remember to check if your bike frame has enough clearance between the left crankarm and chainstay. The power meters have a thickness of 5.5mm (4iiii Precision 3), 7.5mm (Stages), and 8mm (4iiii Precision 3).
More reading : 4iiii Precision 3 vs Precision Comparison
| Comparison | 4iiii Precision 3 | 4iiii Precision | Stages Power Left |
|---|---|---|---|
| Crankarm lengths | 170, 172.5, 175mm | 170, 172.5, 175mm | 170, 172.5, 175mm |
| Accuracy | ±1% | ±1% | ±1.5% |
| Battery type | CR2032 | CR2032 | CR2032 |
| Battery life | 800 hours | 100 hours | 150 – 200 hours |
| Connectivity | ANT+, BLE | ANT+, BLE | ANT+, BLE |
| Max. power | 4000W | 4000W | 5000W |
| Cadence | 30 – 170 rpm | 30 – 150 rpm | 10 to 220 |
| Height | 5.5mm | 8mm | 7.5mm |
| Weight | 9g | 9g | 15g |
| LED indicator | Yes | No | No |
| Waterproof rating | IPX7 | IPX7 | IPX7 |
| Warranty | 3 years | 3 years | 1 year |
| Price | $385 | $335 | $375 |
Spider-based power meters
Choose among the spider-based power meters to fit Shimano GRX cranksets;
- Power2max NG G-X
- Power2max NGeco G-X
- 4iiii Precision Right
| Comparison | Power2max NG G-X | Power2max NGeco G-X | 4iiii Precision Right |
|---|---|---|---|
| Crankarm lengths | 165, 170, 172.5, 175mm | 165, 170, 172.5, 175mm | 170, 172.5, 175mm |
| Accuracy | ±1% | ±2% | ±1% |
| Connectivity | ANT+, BLE | ANT+, BLE | ANT+, BLE |
| Battery | Rechargeable | CR2450 | CR2032 |
| Battery Life | 80 hours | 300 hours | 100 hours |
| Warranty | 2 years | 2 years | 3 years |
| Price | $1,123 | $865 | $465 |
Power2max NG and NGeco gravel
With the Power2max NG and NGeco gravel, you need to replace the GRX810 or GRX600 with a Rotor ALDHU 24 crankarm. You can reuse the existing 1X or 2X chainrings.
More reading : Power2Max NG vs NGeco Comparison
4iiii Precision Right
The 4iiii Precision Right is a right-sided power meter unit built onto the GRX810 crankset. They’re available in 170, 172.5, and 175mm lengths with a single 40T chainring.
The unit is pre-installed at the factory. There is no option to send your existing GRX810 crankset to 4iiii to fit the unit.
More reading : 4iiii vs Stages Power Meters Comparison
Pedal-based power meters
For pedal-based power meters, you can choose between;
- Garmin Rally XC
- SRM X-Power
Pedal-based power meters are the easiest to install by just swapping out the pedals.
| Comparison | Garmin Rally XC200 | SRM X-Power |
|---|---|---|
| Accuracy | ±1% | ±2% |
| Weight (pair) | 441g | 345g |
| Connectivity | ANT+, BLE | ANT+, BLE |
| Battery | LR44/SR44 | Rechargeable |
| Battery Life | 120 hours | 30 hours |
| Cleat type | Shimano SPD | Shimano SPD |
| Pedal stack | 13.5mm | 10.5mm |
| Q-factor | 53mm | 54mm |
| Warranty | 1 year | 2 years |
| Price | $1,200 | $1,300 |
Garmin Rally XC
Garmin Rally XC is the latest power meter by Garmin. It comes in either a left-sided (XC100) or dual-sided (XC200) option.
You’ll need a Shimano SPD cleat, which is included in the box.
SRM X-Power
The SRM X-Power is available in single-sided (left) or dual-sided options for Shimano SPD cleats.
Alex Lee is the founder and editor-at-large of Mr. Mamil. Coming from a professional engineering background, he breaks down technical cycling nuances into an easy-to-understand and digestible format here.
He has been riding road bikes actively for the past 12 years and started racing competitively in the senior category during the summer recently.