Power meters
Velo Sound of Motion powermeter
This is the Velo Sound of Motion, a black power meter for bikes. A power meter measures how much power you put out, in watts.
What you get
- Velo Sound of Motion
- Bike power meter
- Black
Why a power meter?
Heart rate reacts slowly and depends on sleep, heat and caffeine. Speed depends on wind and gradient. Power depends on none of those: 250 watts is 250 watts, uphill, downhill or into the wind. That lets you steer intervals, pacing and effort so precisely that your sessions become comparable.
A good power meter measures with strain gauges that sense how the metal flexes as you pedal. Accuracy is typically between 1 and 2 percent, which is enough for training and pacing. Mind the difference between single-sided and dual-sided. A meter that only measures the left side doubles that figure. That is right as long as both legs contribute equally, and almost nobody is perfectly even.
The location sets the price, weight and convenience. Pedals are easy to move between bikes. A crank or crank arm measures steadily and is easy to fit, but stays on one bike. A hub measures the total at the rear wheel and works with any crank, but stays with that wheel. A spider, the star between the crank and the chainrings, measures both legs together and is often considered very stable.
A power meter says little without context. You need to zero it, pair it with a computer and spend some time learning your own zones, for instance with an FTP test, the power you can hold for roughly an hour.
How the meter location compares
Most meters reach 1 to 2 percent accuracy. The location mainly decides convenience.
| Location | Measures | Advantage | Drawback | Swapping |
|---|---|---|---|---|
| Pedals | Left and right separately | Easy to swap, per-leg data | Cleat and pedal type fixed | Very easy |
| Crank arm or crank | Left, or left and right | Stable and light, often well priced | Stays on one bike, standard must fit | Moderate |
| Spider | Total, both legs together | Very stable, matches its own crank | Often higher cost, needs the right crank | Moderate |
| Hub | Total at the rear wheel | Works with any crank and cleat | Tied to that wheel, also on rollers | By swapping the wheel |
Accuracy is typically 1 to 2 percent, but varies by model and conditions.
Choose it if
- You want to train by watts instead of heart rate or feel
- You are looking at a power meter from a brand you do not know yet and want to compare
- You train in a structured way, with zones, intervals or a plan.
- You want to control your pacing in wind, on hills or in a race.
Choose something else if
- You want a power meter from an established brand with well known support: read the product page first
- You ride mostly for fun and speed and feel are enough for you.
- You do not want to analyse numbers and would rather just ride.
How to use a power meter
Fit it as instructed
Use the prescribed torque. A fitting that is too loose or too tight gives wrong readings.
Pair with your computer
Turn the crank a few times to wake the meter and search for it over ANT+ or Bluetooth on your computer.
Zero it
Do a zero offset before every ride, with the crank still and the bike upright. It removes drift caused by temperature.
Learn your zones
Do an FTP test or follow a plan to set your zones. Adjust them as you improve.
Ride and review
During the ride, use the average over a few seconds instead of the raw peak. Look at the full picture afterwards.
Good to know
- The title does not state the mounting type (pedal, crank or hub), so check it suits your bike
- You need a bike computer or app that can read it
- Check that the meter fits your crank standard, bottom bracket and cassette or drivetrain.
- Look at the battery type and how long it lasts: a coin cell or a rechargeable battery, usually tens to hundreds of hours per charge or set.
- A left-only meter estimates the right leg. If one side is weaker, the figure drifts away from the truth.
- A new crank, chainring or shifter can call for a new calibration. Follow the manual.
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