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Power Meter Types

Power meters have been around for quite some time, dating back to the late 80’s when SRM introduced its first wired system. However, in just the last few years, the power meter market has blown wide open. In addition to power meters with improved features and functionality, 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, explaining how they differ from one another. We also lay out some advantages and considerations of each that you will want to consider when deciding which power meter is right for you. Let’s check em’ out!

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Power Meter Types

When we talk about “type”, we mean where the power meter is located on the bike. 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
  • 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 unit)
  • 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 difficult

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 a pedal-based power meter. Of all the power meter types, pedal-based systems are perhaps the most convenient and easy to use. In addition, they are compatible with just about any bike. These advantages make pedal-based power meters very popular.

Advantages:

  • This design typically allows for easy installation and pedals can be quickly moved between bikes
  • They are compatible with almost any bike since they attach just like a normal pedal
  • You can measure each leg’s power independently (if you purchase a dual-sided system)
  • 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
  • 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 DUO

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. Several manufacturers make a crank-arm based power meter, however there are a few different ways they go about measuring things. In addition, there are both left-only crank arms (power meters that measure left leg power only), as well as complete cranksets that can measure left and right power. When most people talk about crank-arm based power meters, they are referring to left-only crank arms, so let’s start with these.

 

Left Only Crank Arm-Based Power Meter

A 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. Stages Cycling, 4iiii Innovations and Pioneer use an OEM left crank arm (such as Shimano or Campagnolo) and attach their power sensor (strain gauges and electronics) to the inside of the crank arm.

WATTEAM sells the POWERBEAT Power Meter which is a self-installed power meter that attaches to the side of the crank arm. Since the POWERBEAT is installed on the user’s existing crankarm, it sells for less than the options above.

Note that with the Stages, 4iiii and Pioneer power meters, 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 chainstay). So pay special attention to frame compatibility when purchasing these power meters.

Advantages:

  • More affordable than most power meters since you are just buying the left side crank arm
  • Lightweight as these power meters don’t add more than about 20 grams to the weight of the crank arm
  • This design allows for easy installation and swapping of the power meter between bikes (assuming both bikes have compatible cranksets)

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 power meters can lead to less accurate results. For the majority of riders however, this isn’t much of a concern

 

Dual-Sided Crank Arm-Based Power Meter

At a higher cost, Stages, 4iiii and Pioneer also sell complete cranksets with dual-sided power. With their complete cranksets, they attach a second power sensor on the drive-side crank arm. With two sensors, one on each crank arm, these power meters can measure total and well as independent left/right power.

If you want a dual-sided WATTEAM POWERBEAT, you can buy their Dual, which comes with two sensors – one for each crank arm.

Verve Cycling takes a different approach with its InfoCrank Power Meter. The InfoCrank is also a complete crankset (crank arms, spider and chainrings) and also has a power sensor on both the left and right crank arm. However the InfoCrank places its strain gauges within the crank arm – the only power meter manufacturer to do this. The result is +/- 0.5% accuracy, all the way to 3,000 watts.

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 one of the most accurate power meters.)
  • Lightweight as these power meters don’t add more than about 40 grams to the weight of the crankset (with the exception of the InfoCrank which is a bit heavier)
  • 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

Stages Cycling

Stages Cycling Shimano Ultegra Power Meter

4iiii PRECISION

Image of 4iiii Precision Power Meter

Pioneer

Pioneer Shimano Ultegra R8000 Power Meter

Verve InfoCrank

Verve InfoCrank Power Meter

WATTEAM POWERBEAT

The WATTEAM POWERBEAT Power Meter installed on a Shimano crankset

4.  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) 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:

  • 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
  • Of all the types of power meters, the PowerPod is the easiest to transfer between bikes as it simply attaches to your handlebars
  • With an MSRP of $299, it is one of the most affordable power meters on the market

Considerations:

  • The PowerPod requires that you attach a separate speed or speed/cadence sensor to your bike for proper operation (whereas direct force power meters do not)
  • 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 Power Meter

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 an 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. To be clear, this doesn’t make hub-based power meters less accurate, they just measure power a bit differently. 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 (Road)

PowerTap G3 Hub-based Power Meter

PowerTap G3 Rear Disc Hub (MTB)

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 and 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 and ready to help.

Josh Matthew

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