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Power Meter Types

Cycling power meters have been around for quite some time, however in just the last few years, the power meter market has blown wide open. In addition to better power meters, we are seeing new manufacturers enter the market with some different types of power meters. In this article, we want to focus on these different power meter types along with some advantages and considerations of each that you might want to consider before making a purchase decision.

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Power Meter Types

The “type” of power meter refers to where on the bike the power meter measures power. For example, some power meters are built into your crank and measure force at the crank spider. Other power meters are built into the pedals. Currently, there are approximately 7 locations to measure power. They are:

  • Crank (Spider)
  • Pedal
  • Crank arm
  • OFPM (Handlebars)
  • Bottom bracket
  • Hub
  • Chainring

1. Crank (Spider)

A crank-based power meter (crank power meter) is located on the cranks of the bike. They measure torque using a strain gauge positioned inside the crank spider. These units require specific cranks or cranksets, but can be interchanged between bikes, depending on compatibility. A typical crank power meter adds approximately 150 grams to the crankset. Crank-based power meters are some of the most common power meters. They are also the most heavily adopted system by professional athletes.

Advantages:

  • Proven, reliable and accurate. Pros often rely on crank-based power meters for a reason
  • You can find a crank power meter to fit just about any bike (road, MTB, track, cyclocross, BMX, etc.). The SRM Origin for example is itself compatible with a wide range of bikes, simply by changing out the spindle and spacers
  • You don’t have to make any compromises to your component selection. For example, you don’t have to use different pedals (as with a pedal-based power meter) or a different hub (as with a hub-based power meter)

Considerations:

  • Can cost more than some other options. (However this isn’t always the case. For example, the FSA PowerBox Alloy starts at only $649 – and it’s a quality power meter!)
  • Cranksets are not as easy to install or swap out as say a pedal or rear wheel. This makes installing the power meter and moving it between bikes more work

SRM Origin Power Meter

Image of SRM Origin Power Meter

FSA PowerBox

FSA PowerBox power meter

2. Pedal

Pedal-based power meters incorporate strain gauges inside the pedal itself. Favero, Garmin and PowerTap all make pedal-based power meters. Of all the power meter types, pedal-based systems are perhaps the most convenient and easy to use. In addition, they are compatible with a wide range of bikes. These advantages make pedal-based power meters very popular.

Advantages:

  • This design typically allows for easier installation and pedals can often be easily moved between bikes
  • They are compatible with almost any bike since they attach to the crank arm similar to a normal pedal
  • You can measure each leg’s power independently (left vs. right power measurement)
  • You don’t have to mess with your drivetrain (don’t have to change cranks, chainrings, etc.)

Considerations:

  • You must use the cleat system that is specific to your power meter. Currently, all pedal-based power meters use cleats that are similar to LOOK Keo cleats, with the exception of the Garmin Vector, which can be modified to fit Shimano pedals with the purchase of a DIY kit
  • Speedplay pedals remain unsupported by existing pedal-based power meter offerings
  • Currently, no manufacturer offers a pedal-based power meter for your mountain bike

Favero Assioma

Image of Favero Assioma DUO Power Meter Pedals

PowerTap P1 Pedal

PowerTap P1 Pedals

Garmin Vector 3

Garmin Vector 3 Power Meter Pedal

3. Crank Arm

A crank arm-based power meter measures the forces in the crank arm. Verve Cycling sells the InfoCrank, which is a complete crankset (crank arms, spider and chainrings) and has a power sensor on both the left and right crank arm. WATTEAM on the other hand, sells the POWERBEAT power meter which is a self-installed power meter, attached to both crank arms. Since these power meters have a power sensor on both crank arms, they can measure power from both legs independently. Both power sensors combine left and right leg power to give you total power.

At a lower cost, companies such as Stages Cycling and 4iiii sell a left side only power-equipped crank arm.  The left side crank arm doubles your left leg power in order to get a total power figure. This method of calculation assumes that both legs produce the same force. Note that with the 4iiii and Stages, the electronics sit on the inside of the crank arm. Because of this, there exists the possibility of clearance issues with your bike frame (the chain stay). So pay special attention to frame compatibility when purchasing these power meters.

(The advantages and considerations you will see below vary depending on if you are buying a dual-sided, complete crankset offering such as the Verve InfoCrank – or if you are buying a left only crank arm such as the 4iiii PRECISION.)

 

Dual-Sided Crank Arm-Based Power Meter

Advantages:

  • High level of accuracy as the crank arm is an ideal place to measure power. (This is especially true for the InfoCrank which has been certified as the most accurate power meter.)
  • You can measure each leg’s power independently (left vs. right power measurement)

Considerations:

  • You should always be sure your bike frame is compatible before buying a power meter. This is especially true with crank arm-based power meters as there can be clearance issues with the frame and the crank arm
  • Cranksets are not as easy to swap out as say a pedal or rear wheel, which makes moving the power meter between bikes more work

 

Left Only Crank Arm-Based Power Meter

Advantages:

Considerations:

  • You should always be sure your bike frame is compatible before buying a power meter. This is especially true with crank arm-based power meters as there can be clearance issues with the frame and the crank arm
  • If for some reason (perhaps due to a previous injury), you produce more power with one leg versus the other, these cycling power meters can lead to less accurate results. For the majority of riders however, this is not a problem

Verve InfoCrank

Verve InfoCrank Power Meter

WATTEAM POWERBEAT

The WATTEAM POWERBEAT Power Meter installed on a Shimano crankset

Stages Cycling

Stages Cycling Shimano Ultegra Power Meter

4iiii PRECISION

Image of 4iiii Precision Power Meter

4.  OFPM (Handlebars)

Velocomp produces a handlebar mounted power meter called the PowerPod. Unlike direct force power meters (all the other power meter types discussed in this article are direct force power meters) that attach to your drivetrain or pedals and measure your power using strain gauges, the PowerPod attaches to your handlebars. It measures your power through wind measurement – the forces that oppose the rider. This is called opposing force technology. The PowerPod uses an accelerometer, a wind pressure sensor, an elevation sensor and a speed sensor – all to measure power.

Advantages:

  • The PowerPod simply attaches to your handlebars so you can quickly transfer the power meter from bike to bike
  • You don’t have to worry about compatibility because you can use the power meter with any bike. In addition, you don’t have to worry about changing out your components
  • With an MSRP of $299, it is the most affordable power meter on the market

Considerations:

  • In some testing done against an SRM power meter, the PowerPod was shown to be within +/-3% of the SRM. While this level of accuracy is sufficient for most riders, if you are looking for the most accurate power meter types available, you might want to consider a direct force (traditional) power meter

PowerPod

PowerPod Power Meter with PowerStroke Upgrade

5. Bottom Bracket

A bottom bracket power meter is similar to a crank-based power meter in that your current crankset is often replaced for a new, power-equipped one (but not always, as you will see below). However the location of power measurement differs. Bottom bracket-based power meters measure torque in the axle. ROTOR manufactures its INpower and 2INpower power meters. Likewise, Easton and Race Face offer their CINCH power meter.

Advantages:

  • The axle-based design means that the critical components of the power meter are safe from impact, dirt and water
  • The INpower, 2INpower and CINCH all offer compatibility with almost every bottom bracket standard which means there is a high likelihood of compatibility with your bike
  • If you already have a ROTOR crankset, you can add the left-sided INpower for as little as $779. Similarly, if you already have the Easton EC90 SL (road) or the Race Face Next SL (MTB) crankset, you can purchase just the CINCH power meter spindle for $599

Considerations:

  • The INpower and CINCH measure left side power only. (However ROTOR’s 2INpower measures total power including left/right power independently)
  • If you decide to purchase and entire crankset, note that they can take more time to install and are generally not transferred from bike to bike

ROTOR 2INpower

ROTOR 2INpower Crankset Power Meter pictured without chainrings

Easton & Race Face CINCH

Easton CINCH Power Meter Spindle

6. Hub

With a hub-based power meter, the strain gauges are located in the rear hub and measure power through the drive chain. PowerTap remains the only manufacturer of a hub-based power meter. Note that in theory, a small amount of power is lost or absorbed in the drivetrain. Therefore power measured at the hub might be slightly less than power measured at the crank. However this doesn’t make hub-based power meters less accurate, they just measure power a bit differently. To be sure, hub-based power meters have been a go-to power meter for years and they remain a very popular option among cyclists of all levels.

Advantages:

  • Quick and easy installation if you buy a wheelset with the hub pre-installed. Swap out your old rear wheel for your new one and you’re ready to roll!
  • Hub-based power meters are easy to interchange between bikes. This assumes your rear wheels are compatible
  • You don’t have to mess with your drivetrain (don’t have to change cranks, chainrings, etc.)

Considerations:

  • Hub-based power meters aren’t suited as well for racing. In the event of a flat or wheel change, you would lose your power meter. This is of course unless your back-up wheels were also equipped with a hub-based power meter
  • Somewhat limited rim and wheel options

PowerTap G3 Hub

PowerTap G3 Hub-based Power Meter

PowerTap G3 Rear Disc Hub

Image of PowerTap G3 MTB power meter

7. Chainring

PowerTap manufactures the C1 Chainring. Similar to the crank-based power meters discussed above, the C1 measures power at the crank. However the exact location of power measurement is different. SRM for example, measures power at the crank spider. PowerTap measures power on the chainring by locating a sensor on the outside of the small ring. The PowerTap C1 Chainring is the only chainring-based power meter.

Advantages:

  • The PowerTap C1 comes as a complete chainring set that you simply bolt onto your existing crankarms. Therefore, there is no need change out your entire crank or mess with your bottom bracket
  • Great features for the price (ANT+ and Bluetooth SMART, left/right power measurement, long battery life)

Considerations:

  • The PowerTap C1 Chainrings are only compatible with 5-bolt 110 BCD compact cranks
  • Because of the nature of the C1 spider, it can’t take a ring smaller than a 36t

PowerTap C1 Chainrings

PowerTap C1 Chainring Power Meter

Summary – Power Meter Types

As you can see, there are several power meter types. They all have their own set of advantages, price points and considerations. As the market grows and new manufacturers introduce new offerings, we expect even more types to come. If you have questions on anything here, or need any guidance, just give us a call. We’re here to help.

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