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Understanding The Different Types of Power Meters

If you want to get stronger and faster on the bike, a power meter might be your best bet.


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A power meter is an essential tool for the triathlete looking to precisely measure their bike fitness. If you want to know your true effort—expressed in watts—regardless of physiological factors that affect heart rate or external factors that affect speed, power is the way to go. The good news is today’s market is flooded with more options than ever, and there are mainly three different types of power meters based on the location where they measure power: spider-based (the part of your bike between the chainrings and the rest of the crank), pedal-based, and crank-arm based.

Different Types of Power Meters

Spider-Based Power Meters (~$400-$1,000)

These seem (subjectively) to be the most reliable. They also measure the power created by both legs in just one sensor. That means there are fewer bat- teries to change and fewer wireless connections to worry about, as well as less sensors to calibrate compared to dual-sensor systems. Spider-based power meters from companies like Power2Max and Rotor (see our head-to-head) also allow you to use a wide variety of crank lengths, which is a great plus. One inherent disadvantage of these systems is that more advanced metrics and data such as left/right balance are less accurate than dual-sensor systems.

Pedal-Based Power Meter Systems (~$400-$1,000)

These are currently available from a few brands including Quarq (formerly PowerTap), Garmin, and Favero. The main draw to these systems is the ability to move them from bike to bike very easily. Garmin and Favero also both offer more affordable versions of their systems with a power meter in only one pedal, which simply doubles the value to give you your overall reported power. A disadvantage of pedal-based systems is that some of the cleats used with these power-meter pedals lack the adjustability of the Look or Shimano pedals that they tend to replace, and if you are a Speedplay user, you are out of luck. Finally, pedal-based power systems traditionally seem to have more issues than other types of power meters.

Crank-Arm Based Power Meter Systems (~$300-$900)

Power meters like those from Stages and 4iiii use small pods packed with electronics and bonded to the back of one or both of your crank arms. These systems are affordable and have proven to be fairly reliable. Like the pedal-based systems, they can be one or dual sided, and if you opt for dual sided you can take advantage of high-level analysis of your pedaling metrics when paired with the right head unit and computer software (at additional cost). Users of cranks arms shorter than 165mm may need to look to a pedal- or spider-based power meter—while there are a few smaller brands, like InfoCranks, that offer cranks under 165mm, your options are limited.

Face-Off: Power2Max NGeco vs. Rotor INspider

Power2Max NGeco

Approximately $500 for spider only. Cost varies slightly by specific model. competitivecyclist.com

What

The Power2Max NGeco is P2M’s cost-friendly power meter option. The NGeco has 2% accuracy and uses a button type, non-rechargeable battery—compared to its big sister, the NG’s 1% accuracy and rechargeable battery.

Pros

Massive crank arm compatibility. You can install a NGeco power meter on about five different popular aftermarket brands, potentially saving you from having to buy a whole new crankset. Most interestingly for triathletes, you can shorten your crank arm length below 165mm easily by choosing Rotor Aldhu cranks.

Cons

While we didn’t have any issues in our dry weather testing, the battery cover on this unit seems like an afterthought that could easily be knocked off or loosened, letting some water in or the battery out.

This is for

The triathlete on a budget, looking for short crank arm options, a no nonsense power meter, and a great deal.

Rotor INspider

$650 for the spider only. Only compatible with Rotor crank systems. rotorbike.com

What

Rotor’s first-generation spider-based crank arm system. With a slightly higher price than the NGeco, this system boasts 1% accuracy and a very slick rechargeable battery system.

Pros

he INspider is designed to work with Rotor’s Q Ring ovalized chainrings, which claim to ease the dead spot at top dead center of your pedal stroke (they also work well with traditional round rings). Connect the power meter to your smartphone or computer to figure out how to best configure the Q rings or to analyze your pedal stroke with great detail. The INspider uses a magnetic battery charger and the system has a colored LED to indicate the battery level at all times. Our test unit still indicates a full charge after several weeks of riding.

Cons

The system is only compatible with Rotor cranks (see their website for exact models), but their offerings are adaptable to just about every current bottom bracket and frame standard.

This is for

Oval chainring users should be flocking to this power meter system but it’s also great for anyone who wants to dive deep into their pedaling dynamics.

The Winning Power Meter

Rotor INspider. For only a few bucks more, INspider users can take advantage of slightly better precision, rechargeable batteries, and Rotor’s powerful computer and smartphone software to further analyze their rides.