SRM Product Information
SRM, widely regarded as the pinnacle of accuracy and reliability for power measurement, has been manufacturing power meters for nearly 30 years, developing their first system in the late 80’s. SRM power meters represent the ‘Gold Standard’ of power measurement with their +/- 1% accuracy. They provide up to 3,000 hours of battery life and come with a 3-year global warranty. SRM makes a variety of models to fit every bike and budget.
Your SRM power meter will come as a complete crankset – spider, chainrings and crank arms – which makes installation pretty straightforward. You simply remove your existing crankset in its entirety, and bolt on your new one. Note that you also have to install the cadence magnet as well, which sometimes can take a bit of trial and error. The magnet must be located in just the right position in order to trigger the reed switch located inside the power meter or spider.
Most SRM power meters run in the 600-800 gram range, with the SRM Shimano Dura-Ace 9000 power meter weighing in at 768 grams. Remember, when calculating the weight of your SRM power meter, subtract the weight of your current crankset in order to determine the added weight of the power meter.
Left/Right Power Measurement
SRM does not provide left/right power measurement.
SRM power meters run off a proprietary battery. No CR2032 or AA batteries here.
The SRM Shimano Dura-Ace 9000 power meter has a battery life of 3,000 hours – far surpassing the average for a power meter which is around 300-350 hours.
Difficulty to Change
As SRM power meters utilize a proprietary battery, the power meter must be sent back to the factory for a battery change.
SRM power meters transmit data via the ANT+ wireless protocol so they will be compatible with any head unit that supports ANT+, including SRM’s own PowerControl head units.
Accuracy is synonymous with SRM. SRM uses a 144 point calibration protocol against a known mass measured to the exact gram. With precise calibration and its auto-offset feature, the power measurement of the SRM has error of less than 1%. The cycling community has long been publishing peer reviewed research using the SRM as the bench mark for measuring power.
SRM is old fashion, but accurate, when it comes to measuring cadence, using a magnet and reed switch. The magnet is mounted to the frame, typically on the underside of the bottom bracket area, and triggers the reed switch which is located inside the crank spider, with each revolution of the cranks.
SRM recommends you perform a manual auto-offset before each ride in order to ensure accurate power readings. A pre-ride zero offset is common practice for almost all power meters.
The SRM power meter also uses an auto-offset feature to keep your offset value in check. However users have recommended that you turn off this feature as some have reported erroneous auto-offset values. The offset you perform at the start of your ride should be stable enough that you don’t need the unit to auto-offset as you ride. Note however that you can only disable this feature if you are using an SRM PowerControl head unit. This feature cannot be disabled using a Garmin head unit, for example.
Starting February 1st, 2016, all SRM power meters come with a limited lifetime warranty for the original owner. The warranty covers the structural and electronic components of the power meter – it does not cover the crank arms, chainrings or accessories.