Power Meters – What Are My Options

Now that you know how power based training can help you as a cyclist, it’s time to figure out which power meter best suits your needs. With new power meters coming out what feels like monthly, this isn’t meant to be a complete list, but rather a guide to navigate your options.

If there was a heat map for power meter locations, the bottom bracket area would be red hot (no, we are not talking about mechanical doping), with some additional heat coming in the rear hub and the handlebars. At the center of the bike, you have crank, spider, chainring, bottom bracket, pedal/cleat, and insole based power meters. They come in all shapes, sizes, and configurations and offer plenty of options at different price points. Rear hub power meters have also been a mainstay of the power meter market for a number of years, and there are a few options that mount to your handlebars.

Let’s start from the back of the bike and move forward.

Rear Hub

Rear hub based power meters use strain gauges to record the amount of force coming through the drive train and making it to the hub. The great thing about this type of power meter, you can move it from one bike to another, as long as the spacing, axle type, and brake type match. The PowerTap hub based power meters have been around for a number of years. There is not a lot of added weight to the wheel set, and price wise, they are about the middle of the road.

Rear hub based power meters are great since you can custom build wheels with their hubs to get exactly what you are looking for out of your wheels. This is also their biggest disadvantage. If you build a wheel for training, it is probably going to be an aluminum clincher. Many competitive cyclists race carbon wheels though, so if you want to race with your power meter, you’ll either need two wheel sets with power meters, or be prepared to race and train on the same wheel set. If you are looking to move the wheel from one bike to another, you’ll also need to consider brake type (rim vs. disc) and axles. If you are running standard quick release with rim brakes on your road bike and thru-axles and disc brakes on your cross bike, you are out of luck.

If you are looking for more detailed information beyond how much power you are putting out, you’ll probably need to look to other power meters. Left/Right power measurement is becoming a more popular feature in power meters, and rear hub based power meters just can’t provide this information.

Crank/Spider

Crank based power meters are the most popular part of the market. They can measure power from three different areas, the spindle, crank arm, and spider.

An example of a spindle based power meter would be the Rotor InPower. The InPower measures the power from strain gauges and accelerometers in the spindle. Putting the extra weight in the spindle is a trick pro mechanics will use to help bikes meet the UCI’s minimum weight limit, so putting the added weight of the power meter here seems like a good choice. A drawback in the InPower’s case is it is only measures on the left side.

The crank arm based power meter is growing rapidly, but it was Stages that started it off with the first successful non-driveside crank arm power meter. Pioneer and others have gotten into the game, but Stages is one of the few brands (if not the only brand at this point) that is offering these types of power meters in carbon. Typically, brands are taking other brands’ non-driveside crank arms and attach epoxy a pod to the inside of the arm of an aluminum crank. These pods hold the strain gauges that are used to measure the power and also cadence. If you are running the same crank across multiple bikes, transferring the arm from one bike to another (and possibly swapping pedals) is all that is needed to be done. On the downside though, if you have different cranks, this doesn’t work. Also, power is only recorded on the left side.

Spider based power meters are where it all began. SRM (Schoberer Rad Messtechnik) started making power meters back in 1986. The original units weren’t the portable units we think of today. Eventually though, designs became more compact, while also becoming more intricate. Today, an incredible amount of information can be gained from them. SRM is still considered one of the leaders in the game. Their units are used as reference points for many other brands out there. They also have a specific head unit that has a very distinctive look.

Pioneer is another brand that is putting out a power meter that provides incredible amounts of information, some of which is very unique. Their model has a distinctive pod that sticks out from the spider arms on Shimano Ultegra and Dura-Ace cranks. With the addition of a non-driveside pod located on the inside face of the crank arm, Pioneer offers left/right power readings. Along with measuring your cadence, Pioneer also measure what they call Force Vector, or the direction you are putting the power down. We’ll dive into this more in an upcoming review of their SGY-PM68 power meter and SGX-CA500 computer.

There can be a few drawbacks though. Some require you to mount magnets onto your frame for cadence measurement or as a reference point. As with other power meters on the crank, portability from one bike to another can be an issue. Price used to be a major hurdle as well, but as the market becomes more saturated, prices have been falling.

Chainring

Chainring based power meters are still pretty new. PowerTap has worked with FSA to develop this area. Instead of putting the strain gauges inside the crank arms or on the spider, they are attached to the chainrings. This  simplifies potential clearance issues with your frame and should make it pretty easy to transfer them from one bike to another, as long as you are using a similar crank. For example, if you are running an FSA crank with a 5-arm spider on your road bike, and a Shimano crank with a 4-arm spider, they will not be compatible.

Other potential issues are replacing worn chainrings, chainring sizes, and specialty rings like oval rings. To use the C1 as an example again, you can buy replacement chainrings, but they suggest that you have the power meter recalibrated after installation. You are also locked into one chainring combination. With other power meters, you can switch ring sizes for different disciplines, and still use your meter. If you are a fan of oval rings like I am, chainring based power meters are not for you.

Pedal/Cleat

Pedal and cleat based power meters are starting to make headways into the power world. There are a few different options out there, but some use sensors in the axles, some in the body of the pedal, and some in the cleat itself. Garmin, Polar, and PowerTap are some of the players in the pedal based power meter game, while Brim Brothers is the sole maker of cleat based power meters. If you currently use Shimano or Look pedals, you’re in luck since most of the pedal power meters use these types of cleats. A plus for both of these types of power meters is that many can be bought as single sided power meters and be upgraded to a dual-sided power meter by buying additional pieces. While they can be transferred between bikes pretty easily, they are only for the road at this point. If you want to swap it over to your cross bike and use your Shimano SPD or Crank Brothers pedals, you are out of luck.

The Brim Brother’s cleat power meter is interesting because you can use just about any road based pedal system. The sensors mount under your cleat, with a pod attached to the top of your foot. The pod is rechargeable and hopefully, you can buy additional sensors kits for additional pairs of shoes. If not, that could be an issue. Also, if you use a shoe that does not have a strap, say the Giro Empire, you might have difficulty attaching the pods.

 

Insole

Insole based power measurement is one of the newer options. RPM² has created an insole system that measures both left, right, and total power from the four courners of your feet. They were originally launched for runners, but have made their way into the triathlon world, and now cycling. The brand is sponsoring the Cylance Pro Cycling team to help develop the insoles even further.

With how new this product is, there are still some unknowns. There is the potential to add even more types of information than already collected by other power meters, but things like battery life, long term durability, and accuracy is still an unknown.

Handlebar

Another rather new area for power meters is the handlebars. iBike started their category with what is essentially a head unit with a power meter built in. Under a new name, Velocomp has since completed a successful Kickstarter campaign and launched their PowerPod. What makes this category unique is that they do not use traditional strain gauges like other power meters. Instead, they use wind pressure, speed, and other sensors to calculate your power.

Since the power is not being directly measured, one could argue that these are theoretical power numbers. I haven’t had a chance to test one yet, but we are hoping to get a PowerPod into the BWN test center soon. From others that have tested it, reports are that the numbers are pretty accurate.

If you are looking for a power meter that can be swapped between bikes easily, this is probably one of the easiest options to move

Online

One final method that doesn’t really require anything more than a GPS cycling computer and the internet would be online sites like Strava.com. Even if you don’t have a power meter, Strava has a way of estimating your power numbers for a ride. In the short term, it is the cheapest option out there.

With that being said, there are some drawbacks. First, the number is estimated. Strava has some great algorithms to calculate your numbers, but the power is not being measured directly from the effort you are putting out. Also, you can’t see these numbers while you are riding. If you are looking to do specific power based intervals, a websites can’t help you there. You also lose more detailed information like left/right measurement.

Other Things To Consider

Battery replacement – Can you replace it at home, or will you need to send it out to be replaced? What kind of battery does it use, and how easily is it to find?

Bluetooth and ANT+ compatibility – This will determine what cycling computer you can use. Garmin computers are ANT+, while others like the Wahoo Elemnt are ANT+ and Bluetooth compatible. Many of the power meters that are coming out broadcast in both formats.

Warranty – Hopefully you will not have to use it, but you never know. Having a good warranty give you some piece of mind that your power meter will last.

Calibration/Service – How hard and how often does the power meter need to be calibrated? This could be as simple as calibrating it through the connected cycling computer, or as in-depth as needing to be sent out to the manufacturer. This could leave you without the power meter during part of your training.

Conclusion

That all might be a little overwhelming, but take some time and think about how you will be using the power meter, the bikes you will want to use it on, and your budget. Take a look at the various power meters on the market, and read more about what they have to offer.