SRM has been making power meters since the late 80’s. They are best known for their crankset-based units, however have recently rolled out pedals options as well. Available for road, MTB, track and BMX, SRM power meters are some of the most precise and consistent power meters available. They are also some of the more costly. Their flagship power meter is the SRM Origin. It features a LOOK carbon crank arm with Trilobe Technology, a rechargeable battery, +/- 1.5% accuracy and a full 3-year warranty. You can also configure it with a range of different chainrings or spindle sizes.
SRM power meters typically come as a complete crankset – spider, chainrings and crank arms. Installation requires you to remove your existing crankset and replace it with the SRM. Assuming you are not changing bottom brackets, this is a pretty straightforward process, but is more involved than say installing a pedal or crank arm.
Their pedal power meters are a bit easier to install. While there are some quick one-time set-up steps, they largely install like a normal set of pedals
Most SRMs run in the 600-800 gram range, with the SRM Origin weighing in at 599 grams, the lightest of the bunch. Remember, when buying a power meter, you are concerned about added weight. Therefore, determine added weight by subtracting the weight of your current crankset.
SRM crankset power meters measure power at the crank spider. Therefore, they measure both left and right leg power. However, unlike some other crankset-based power meters, they do not measure left/right power balance.
SRM pedal power meters have a senor in each pedal and therefore can measure the power from both legs in addition to independent left/right power.
What sets the SRM power meters apart is their accuracy. They have been making power meters longer than anyone and have the process down to a science. Most units feature SRM’s 144 point calibration protocol, resulting in accuracy up to +/- 1.0%. Most units also come with a full three-year warranty. This compares to one or two years for other power meter brands.
With most SRM power meters, you have your choice of a rechargeable battery or standard battery (the pedals come with a rechargeable battery only). Most customers opt for the rechargeable, which features 100 hours of battery life. SRM’s standard batteries have a very long battery life, typically around 2,000 hours. However the power meter must be sent back to the factory for a battery change.
SRM power meters support the ANT+ wireless protocol. Therefore, they are compatible with any head unit that supports ANT+, including SRM’s own PowerControl head units.
The SRM pedals also support Bluetooth SMART. This is a nice feature and allows the power meters to be used with smart phones as well as with popular indoor training apps such as Zwift.
Accuracy is synonymous with SRM. The company uses a 144 point calibration protocol against a known mass measured to the exact gram. This results in an error of less than 1.0% in most cases, better than the industry standard.
These power meters use a magnet to measure cadence. The magnet is mounted to the frame, typically on the underside of the bottom bracket area. It triggers the reed switch which is located inside the crank spider. While mounting a magnet to the frame is an additional step, magnet-based cadence measurement is considered the most accurate.
SRM power meters come with a three-year warranty which covers the product from defects in material and workmanship. This compares to one or two years for other power meter brands.