Power meter position is likely to be a key factor in your purchase. Power meters measure wattage via strain gauges from one of four positions on the bike: the rear wheel hub (PowerTap), pedal (Garmin, LOOK), crank (Stages, Rotor, Pioneer) or crank spider (SRM, Power2Max, Quarq).
If you have one bike – or a number of bikes and deep pockets – then you can take you pick from the full marketplace, though a crank or crank spider-based power meter will allow you to pick whatever wheels and pedals you like.
However, if you want to record your wattage across a number of bikes – a training bike and race bike, for example – then your choice drops significantly if you want to be able to move the power meter between bikes quickly and easily, though Mill believes it is more important to train with power and to then take that knowledge into racing.
“It’s great to have data in racing but, because of the cost implications, I would much prefer to have my riders train on power than race,” says Mill. “Use it for training, make the most of your training, understand how your body feels, then take that in to racing, when, unless it’s a time trial, you’re unlikely to be able to dictate the pace anyway.”
Riders who want a power meter than can be used across a number of bikes are likely to be swayed towards a wheel or pedal-based system like PowerTap or Garmin Vector.
Other key factors to consider when buying a power meters are:
- The quality and breadth of data available. Garmin Vector, to name one example, provides left and right power measurement, while Stages only measures left leg power and then doubles it to estimate total power.
- Temperature variation. Stages and Rotor are among the power meters – and many don’t – to recalibrate according to temperature.
- ANT+ and Bluetooth compatibility. What computer do you want to display your power data? SRM, Garmin, Rotor, PowerTap and Quarq all transmit data via ANT+, while Stages uses both ANT+ and Bluetooth.
- Serviceability. SRM’s power meter, for example, needs to be sent to a service centre to have the battery changed.
Mill and Gallagher both agree that a power meter from a major manufacturer is likely to provide accurate data to within plus/minus two per cent, but that doesn’t make it any easier to find the right system for you. Like when buying a bike, there’s no simple answer as to what power meter you should buy, but over the following pages we’ll run through six of the leading power meters on the market.