4iiii Shimano GRX RX810 Precision 3+

The 4iiii GRX RX810 Precision 3+ power meter is a single-sided powermeter for cranks of the Shimano RX810 series. It measures the power at the left crank arm. The 4iiii power meter is now available in the 3rd generation. The actual powermeter weighs in at only 9g and sits well protected inside the left crank arm. The widely used CR2032 battery lasts for a whopping 800 hours of operation of the powermeter. The measurement accuracy is ± 1%. For mounting the 4iiii Power L GRX RX810 you need the TL-FC16 tool.

Single-sided measurement

With the 4iiii Precision 3+ power meter, only the left crank arm is equipped with measurement electronics. The power is doubled to estimate the total power. Staying in your training zones or pacing a long climb or a triathlon usually works very well with a single-sided power meter. It becomes more difficult when one leg is significantly stronger than the other. Then the total power deviates. The 4iiii is therefore particularly suitable for riders who can do without the few last percent of accuracy.

Compatible bikes and cranks

The power meter is mounted on the inside of the crank arm. Therefore, 10mm space is required between the crank arm and frame. With direct-mount brakes it is often too tight. You can check with a 10mm allen wrench whether a 4iiii power meter fits onto your bike. In the power meter area, the 10mm allen wrench must fit between the frame and crank arm:

The special thing about Shimano: the Stages Shimano GRX RX810 power meter fits not only to cranks of the same series, but to all Hollowtech II road cranks (eg 105 R7000 or Ultegra R8000). However, the Q-Factor is slightly larger on the GRX RX810 series. This means that the pedals are 2.5mm further away from the frame. So if the Stages Shimano GRX RX810 Powermeter is used with a road crank from the 105 or Ultegra series, then the left pedal is 2.5mm further out than the right pedal. This difference is quite small and most riders wouldn't notice the difference. In addition, you can move the cleat on the shoe a little.
Therefore, since Shimano gear is most often found on road bikes, the Stages GRX RX810 power meter is ideal for bringing it along to a training camp - provided that the rental bike also has a Hollowtech II road crankset.

Compatible bike computers and smartphones

Thanks to ANT + and Bluetooth Smart, the 4iiii power meter is compatible with all ANT + enabled bike computers and smartphones with Bluetooth Smart technology. With Bluetooth Smart, the 4iiii power meter works with Zwift, TrainerRoad, Rouvy, The Sufferfest and other indoor-training apps.

Construction and design

The left-hand 4iiii power meter sits well protected in a flat plastic housing on the inside of the left crank arm. Not everyone has a perfect pedal stroke. The forces acting on the pedal crank change when you sit, stand to climb a steep hill, or sprint. In addition, the way your legs apply force to the pedals changes as you become fatigued. To ensure that the force applied to your crank is measured precisely, 4iiii uses a patented 3D strain gauge technology. Power is measured by lateral flex, pull and twist of the crank. Cadence is measured using accelerometers. The 4iiii Powermeter is permanently connected to the left crank arm. This is therefore always included in the pack. The 4iiii Powermeter has the water resistance class IPX7.

Battery

The 4iiii Shimano GRX RX810 power meter is powered by a standard CR2032 button cell. A battery is sufficient for about 200 hours of operation time. The CR2032 is widely used and inexpensive. It is available at almost every supermarket. The battery can be changed without tools. The LED on the power meter provides information about the battery level.

Weight

The actually power meter has a low weight of just 9g and is the lightes power meter on the market.

Accuracy

We were able to confirm the accuracy of +-1% several times on our calibrated Cyclus II ergometer in the laboratory and in comparison with other power meters on the road. The measurement accuracy must be put into perspective somewhat, since the measurement is only one-sided.

Cadence

The cadence is determined by means of an accelerometer and an integrated ring laser and transmitted to the bike computer or smartphone. An additional cadence sensor is no longer necessary.

Temperature compensation

When temperatures change, different materials expand differently. This can have a significant impact on the measurement accuracy of a power meter, as the strain gauges react to even the smallest changes. The 4iiii power meter therefore has active temperature compensation. This means that it delivers precise measurements even when temperatures change.

Calibration

Each individual 4iiii power meter is individually calibrated at the factory. Something else is the zero calibration (also called "Zero Offset" or "Manual Zero"), which should be done before every ride. This is similar to a scale that also "zeros" itself before weighing. For zero calibration, the 4iiii power meter must be active and connected to the bike computer or smartphone. The zero calibration can be performed on the bike computer or smartphone.

Setup / Firmware Updates

Unlike other power meters, the 4iiii power meter does not need to be specially set up or registered. The correct crank length is already stored in the power meter. Firmware updates require the 4iiii App (Android & IOS) and a smartphone. We recommend always using the latest firmware of the power meter and the cycling computer.

Installation

The installation of the 4iiii power meter is very simple. The left crank arm of your crank is simply replaced by the 4iiii crank arm. For the 4iiii Shimano GRX RX810 power meter you need a 5mm allen wrench and the Shimano TL-FC16 crank assembly tool. It's needed to loosen or tighten the bolt that pulls the left crank onto the axle.

Durability

We have made good experiences with the durability of the 4iiii power meter. Due to its placement on the inside of the left crank, the power meter is well protected against mechanical influences. In a crash, for example, a pedal power meter usually gets somewhat beaten up. This is where the 4iiii can score.

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Warranty and support

The 4iiii power meter comes with a 3 manufacturer's year warranty. The 4iiii power meters are manufactured in Canada. 4iiii also has European distribution in the Netherlands. If there is ever a problem, we have a direct line to 4iiii Europe and can help you quickly.