What is Power? What is a Power Meter?
If you’re familiar at all with cycling, or training for cycling, you’ve probably heard of watts. Watts, or power, is a way of measuring the amount of work done in cycling. Unlike speed or heart rate which can be influenced by other things, power will always be consistent. If you measure 100 watts of force on one day, that will be the same amount of force the next day and the day after that.
I’m not going to go into too much detail about how this number is generated or why it’s helpful to your and your coaches. It is, however, extremely helpful in training. Buying a device to measure power output (a power meter) is one of the best upgrades you can make. There are many devices that can measure power, some more accurately than others, and we typically recommend two types at the shop: crank or pedal power meters. We find these devices are the most accurate, reliable, and durable of all devices we’ve tested.
Crank Power Meters
First off, let’s look at crank power meters. Crank power meters such as the SRAM DZero measure strain between the crank spider and the chain ring bolts. Whether the force is applied on the left or right side, the power meter will measure it. Additionally, we find that the weight is centralized closer to the rotational axis. Finally, the delicate electronics are closer in to the center of the bike. All these combine to make crank power meters the most accurate and reliable of any power meter.
Hoewver, for trade-offs, the crank power meters are varied based on bottom bracket and difficult to change. They require specialized tools to install and removed, and are not typically compatible between any two given bikes if you ever wanted to switch it. However, by checking your bottom bracket specifications, we’re happy to help you determine the correct option for your bike. If you purchase the power meter through the shop, we’ll install it free of charge.
Pedal Power Meters
When looking at pedal based power meters, their biggest benefit is interchangeability. Most bikes, even comparing something as different as a commuter bike and a track bike, use the same size pedal thread. Swapping out pedals is an easy operation most riders are familiar with. Thus, the compatibility and exclusivity of different types of crank based power meters are solved by using pedals. They are thus a bit easier to re-sell, much easier to change between bikes, and all around are quite user friendly. Additionally, pedals can sometimes give you more interesting data than a simple power number. The Garmin Vector 3 can even measure time seated vs. standing, as well as the exact start and stop of your power phase! (For more info on what a power phase is, check out coach Erin’s article on cycling drills!)
However, the major drawback is weight and fragility. Pedals are the most exposed part of the bike when riding and transporting the bike. Spinning hundreds of dollars of equipment around 90 times per minute can be a detriment of something goes wrong. Additionally, these pedals are typically a bit heavier than a non-power pedal. The Powertap P2s weigh in at 400 grams, almost 150 grams heavier than an Ultegra pedal. 150 grams may not seem like much, but consider adding on that weight to every pedal rotation. You can then understand the benefits of lower rotational weight.
Let us help you!
Choosing the right power meter can be daunting, but we’re happy to work with you to make the right choice. Reading power numbers can give you and your coaches an objective view of how you’re performing. It’s incredibly helpful for training, and good information to know! Just a reminder, not only will we consult for free on what the best option for you is, if you purchase the part through us, installation is free as well!