POWER METER 101
IT’S ALMOST BECOME a “must-have” piece of equipment these days—measuring your power on the bike, for many, is as important as being able to monitor speed and distance. A power meter can be a great tool to help track your improvement, and many people use it to gauge their efforts both in training and racing.
It wasn’t long ago that a power meter would set you back thousands of dollars, but these days there are lots of options at a variety of price points. You can learn more about the different models in our Buyer’s Guide—what we’re going to focus on here are the most popular types of power meters—Spider, crank and pedal offerings—and the pros and cons of each style. (Power meters based in the wheel hub used to be popular, but the added wheel weight has made those less popular. You can also find axel-based and aero power meters, but those aren’t as common as the ones we’re going to focus on.)
Regardless of the type of power meter you get, the unit will use strain gauges to measure the amount of force you’re putting into the pedals. The difference is where that force is being measured.
When it comes to accuracy, you’ll pay more for power meters that provide more accurate measurements, but that’s not necessarily as critical as it might seem. If the unit is providing consistent measurements, then you’re going to be able to gauge your efforts accordingly.
Spider-based power meters
The “spider” is what the chainrings on your bike attach to. This type of power meter registers the load that’s being placed on both crank arms (an important distinction—you’re getting power measurement from both legs). The SRAM/Quarq and SRM power meters use this technology—they tend to be more expensive, but are extremely accurate.
Crank-arm power meters
As the name implies, these power meters measure the amount of strain the crank arm is being put under. An example of this type of power meter is the Precision 3 from 4iiii, which is easily added to your bike setup. Typically these power meters are a lighter option and relatively easy to add to your existing setup.
Pedal power meters
This is the easiest option when it comes to adding power to your cycling mix, and one huge advantage is that you can easily move them from bike to bike. Garmin’s Rally pedals are one example of this type of pedal system.
Separate leg measurement
Many of the less expensive power meters will only measure one leg. The power numbers from that one leg are doubled to give your power output. It’s still a useful measurement, and one that can give you some useful data, but if you’re looking to figure out if there are discrepancies between your left and right legs in terms of power output, you’ll want to invest in a power meter that accommodates that.
Higher-end power meters will also provide analysis of your pedal stroke, which is a great way to monitor and improve your pedalling efficiency.
So, when it comes to picking up a power meter for your bike, figure out exactly what you’re after—just a simple power number to gauge your efforts? Or are you looking for more detailed analysis. Another factor to consider is whether or not you want to be able to switch your power meter from one bike to another—if that’s the case, a pedal-based option is a no-brainer.—KM