Road power meters

How to choose your power meter

A power meter measures the work you actually produce, in watts, regardless of wind, gradient or fatigue. It is the one training metric that does not lie. The choice comes down to three things: where the meter is fitted, whether it measures one leg or both, and what you already have on your bike.

Where to fit the power meter

• In the pedals (Favero Assioma, Garmin Rally, Wahoo Speedplay Power): this is the easiest setup to install, using a 15 mm spanner, and the only one that moved from one bike to another in two minutes. Ideal if you have several bikes or are travelling.
• In the crankset or spider (Shimano R9200-P and R8100-P, SRAM Red and Rival AXS, Quarq): the most discreet and stable solution, regardless of pedal type. In return, it requires a compatible bottom bracket standard and cannot be transferred between bikes.
• In a single crank arm : the lowest-cost entry point for crank-based power measurement, but it only reads one side.

One leg or both

• A power meter without shifting (single-sided) measures the left leg and doubles the result. The reading is entirely repeatable — which is what matters for tracking progress — but it will be inaccurate if you have a pronounced imbalance.
• A power meter dual-sided measures each leg separately. It provides theleft/right balance and an accurate power reading. This is the main reason for the price difference across the range.
• With both Favero and Garmin, you can start with single-sided measurement and upgrade to dual-sided later by adding the second unit.

Understanding Garmin Rally model numbers

• The two letters indicate the pedal body : RK for Look Keo, RS for Shimano SPD-SL, XC for SPD.
• The number tells you the rest: 100 single-sided, 200 dual-sided.
• The versions 110 and 210 are conversion kits — instrumented axles and fasteners, without pedal bodies. They fit into pedal bodies you already own.

Accuracy and battery life

The stated accuracy is around ±1 % on top-end models, ±2% elsewhere. As with a turbo trainer, repeatability matters more than the absolute value as long as you use the same device. For power, there are models with a rechargeable battery (Favero, around 50 hours) and models with a replaceable battery, which are easier to replace while travelling. All transmit via ANT+ and Bluetooth.

Compatibility to check

For a power meter pedal : the cleat that matches your chosen pedal body, and a tightening torque often model-specific. For a power meter crankset : the frame’s bottom bracket standard and axle diameter. In every case, also check the clearance between the crank arm and chainstay, which is insufficient on some frames.

Spare parts

Much of the range consists of Favero spare parts: bearings, left or right pedal bodies, magnetic connectors, chargers and cables. A pedal power meter that takes a knock can be repaired rather than replaced: the body can be changed without touching the instrumented axle, which is the expensive part.

To find out more: How to choose your power meter

See also: Road pedals · Road cranksets and crank arms · Turbo trainers and rollers