Which Power Meter Fits A Shimano GRX Crankset?

Founder, Mr. Mamil
Shimano GRX Crankset
Shimano GRX Crankset

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

4iiii Precision 3 power meter for Shimano GRX 810
4iiii Precision 3 power meter for Shimano GRX 810

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
Comparison4iiii Precision 34iiii PrecisionStages Power Left
Crankarm lengths170, 172.5, 175mm170, 172.5, 175mm170, 172.5, 175mm
Battery typeCR2032CR2032CR2032
Battery life800 hours100 hours150 – 200 hours
ConnectivityANT+, BLEANT+, BLEANT+, BLE
Max. power4000W4000W5000W
Cadence30 – 170 rpm30 – 150 rpm10 to 220
LED indicatorYesNoNo
Waterproof ratingIPX7IPX7IPX7
Warranty3 years3 years1 year
Left-sided crankarm power meters for Shimano GRX810

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
ComparisonPower2max NG G-XPower2max NGeco G-X4iiii Precision Right
Crankarm lengths165, 170, 172.5, 175mm165, 170, 172.5, 175mm170, 172.5, 175mm
ConnectivityANT+, BLEANT+, BLEANT+, BLE
Battery Life80 hours300 hours100 hours
Warranty2 years2 years3 years
Spider-based power meters for Shimano GRX810

Power2max NG and NGeco gravel

Power2max NG G-X with Rotor ALDHU24 Crankarm
Power2max NG G-X with Rotor ALDHU24 Crankarm

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

4iiii Precision for Shimano GRX
4iiii Precision Right for Shimano GRX

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.

ComparisonGarmin Rally XC200SRM X-Power
Weight (pair)441g345g
ConnectivityANT+, BLEANT+, BLE
Battery Life120 hours30 hours
Cleat typeShimano SPDShimano SPD
Pedal stack13.5mm10.5mm
Warranty1 year2 years
Pedal-based power meters for Shimano GRX810

Garmin Rally XC

Garmin Rally XC200
Garmin Rally XC200

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

SRM X-Power
SRM X-Power

The SRM X-Power is available in single-sided (left) or dual-sided options for Shimano SPD cleats.

Alex Lee at Mr.Mamil

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.