Power Meter Types

2. Pedal

Pedal-based road power meters incorporate strain gauges inside the pedal itself. Favero Electronics, Garmin, and SRM/LOOK all make a pedal-based power meter. These power meters come with proprietary, LOOK Keo style cleats that must be used with the pedal. Of all the power meter types, pedal-based systems are perhaps the most convenient in terms of compatibility and installation. These advantages make them one of the most popular power meter types.

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 (note the SRM/LOOK EXAKT takes a bit more work to install)
• You can measure each leg’s power independently (if you purchase a dual-sided system)

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. Note that Favero, Garmin and SRM/LOOK pedals can also be used with original LOOK Keo cleats
• Speedplay pedals remain unsupported by existing pedal-based power meter offerings

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 left-only crank arms (power meters that measure left leg power only), as well as complete cranksets that can measure left and right leg 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

A left side crank arm-based power meter 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, electronics and battery) to the inside of the crank arm.

Note because the electronics sit on the inside of the crank arm, there exists the possibility of clearance issues with your bike frame (the chainstay). So pay special attention to frame compatibility when purchasing these power meter types.

Advantages:

• More affordable than most power meter types since you are just buying the left side crank arm
• Lightweight as these power meters only add about 10-20 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 left only 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

At a higher cost, Stages, 4iiii and Pioneer also sell complete cranksets. With their complete cranksets, they attach a second power sensor on the inside of 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.

Verve Cycling takes a different approach with its InfoCrank IC2 Road 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 20-40 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. This makes moving the power meter between bikes more work

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 models starting at $249, it is the most affordable power meter 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 +/- 3.0% 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

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 2INpower DM and INpower DM power meters.

Advantages:

• The axle-based design means that the critical components of the power meter are safe from impact, dirt and water
• The 2INpower DM, INpower DM and CINCH all offer compatibility with almost every bottom bracket standard which means there is a high likelihood of compatibility with your bike
• More affordable than some other power meter types as the INpower DM and CINCH sell for $715 and $599, respectively

Considerations:

• The INpower DM and CINCH measure left side power only. (However ROTOR’s 2INpower DM 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 between bikes

Summary – Power Meter Types

There are several power meter types and they all have their own set of advantages, price points and considerations. Remember, with power meters it’s never about better or worse. Rather it’s about finding one that fits your budget, is compatible with your bike and offers the features and functionality you desire. If you have questions on anything here, or need any guidance, just give us a call. We’re here and ready to help.