Our power meter may be small in stature, but it packs a technological wallop.
Our Stages Power meter is downright miniature. The 20g unit houses an array of high technologies adapted from the rapid advancement of modern electronics.
Our accelerometer based cadence measurement is possible due to the technology's development for use in smart phones. We’re especially excited about the Stages Power meter’s bilingual communication between both ANT+ and Bluetooth Smart protocols; the latter gives us the ability to ‘future proof’ this power meter with the ability to update its firmware over the air using an iPhone 4S or iPad 3 (or later) devices, while also keeping its housing impenetrably sealed to the elements.
Ultimately, we believe the Stages Power meter offers the most advanced technology of any power meter currently on the market, yet is one of the easiest to install, maintain, and simple to use. To dive deeper into the technology making up the Stages Power meter, select a link below.
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Accurate readings and smart design
We’re measuring power with strain gages that measure force in kilograms and converting it to power via simple physics equations. The major difference between Stages Power and our competitors, however, is that we’re measuring force on the left crank arm. In turn they measure power at the crank’s spider.
Measuring power at the left arm requires one assumption — that your left and right legs have a balanced power output. We have found with thousands of miles of testing, that power differential between legs has no significant influence on ride data and its value as a training tool. This assumption is the tenant to our ability to keep the complexity and cost of our system lower, all the while providing power measurement with ±2% accuracy (of the left leg's measured power).
Our assumption of symmetry also gives major advantages over spider based torque measurements, which are forced to add complex algorithms or geometries in order to filter out unwanted torque measurements coming from chain line and crank position.
By measuring force at the arm we’re able to use the orientation of our strain gages to geometrically filter any unwanted measurements of deflection. Our left measurement also makes our calibration simpler and more accurate, due to the fact we do not have to compensate for torque differences due to chain line induced flex in the spider or chainring stiffness. This orientation also helps us compensate for temperature changes, which we further back with factory calibrated, software based temperature compensation.
Likewise the use of accelerometer based cadence allows the Stages Power meter to know if you’re pedaling in less than a second. And from the rider’s perspective one of the clearest advantages to accelerometer-based cadence is the elimination of glued or zip-tied magnets, allowing our unit to be completely self-contained.
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Size and Weight
The Stages Power meter is factory assembled to a non-drive side crank (it cannot be purchased alone); this means you can add a power meter to your existing crank by replacing the left arm only. To facilitate this we sell a variety of Cannondale, Shimano, and SRAM power measuring left arms, separately. The Stages Power meter adds just 20g to a manufacturer’s existing crank arm, and measures a petite 65x30x10mm in dimension. Mind you this weight and size package represents everything needed to capture power and send it to your computer, including: the battery, and cadence sensor. The Stages Power meter's small size and lightweight put it in a class of its own.
The meter itself is between 33g and 185g lighter than much of the competition, and that’s before you factor in the competition’s required additional magnets or hardware, of which the Stages Power requires none. Additionally, the Stages Power meter is highly sealed against environmental conditions. The power meter’s housing is made of a polycarbonate blend, which is a similar material to that used in bulletproof glass and your favorite sport sunglasses. We find this material perfect due to its superior durability and flexibility, so there is very little chance of breaking the housing before irreparably damaging the crank.
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ANT+ & Bluetooth Smart
The Stages Power meter is the first power meter to add the new Bluetooth Smart protocol, which offers an extended range compared to standard Bluetooth. Bluetooth 4.0 (at the device end) offers one major benefit for our application: the ability to communicate both to and from our meter for true two-way communication. This allows the Stages Power meter to both send power data to your phone or Bluetooth enabled head unit, but also allows us to use your phone to send firmware updates to the power meter without need for an external wire port.
There's one other added benefit of Stages Power meter’s use of Bluetooth Smart, the ability to upload a ride captured on your iPhone directly to Strava or Training Peaks before you even take your helmet off. Once you have recorded your ride information, you need to get it out of the meter to save, upload, and analyze. To do this the Stages Power meter includes two communication protocols: ANT+™ and Bluetooth Smart.
ANT+ is the gold standard for over-the-air communication in the cycling and athletic industries. The system is simple, robust, and well accepted thanks to the proliferation of Garmin's GPS display units. Our ANT+ antenna provides for those riders looking to add power to their ANT+ devices, whether from Garmin or another manufacturer
By including both ANT+ and Bluetooth Smart communication, the Stages Power meter gives riders all options. In essence, it's future-proof, and you need not worry about where the head unit category goes in the future.
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Left arm based strain gage
Stages Cycling achieves the Stages Power meter’s amazing weight and price by melding contemporary technology adapted from today’s rapidly evolving electronics industry with an elegant design that measures power effectively and discreetly at the left crank arm.
"There are several good products in the market costing $2000 or more, each with its own advantages and disadvantages," said Doug Crawford, VP of Product Development for Stages Cycling. "Our approach was to clearly focus on both rider needs and the opportunities not addressed by current offerings. We then applied the best available technology to deliver a simple yet elegant solution for direct power measurement that is unique in its implementation. We stripped away some areas of system complexity, but added new and emerging technology in order to provide riders with exciting new benefits in several critical areas.”
This goal required Stages Cycling’s power meter solution to be simpler, lighter, and less expensive than any other power meter in the market. This required out of the box thinking to reach a less complex solution that meets the same end, and reaching that solution took considerable development time.
The Stages Power meter uses a custom strain gage array to measure power at the left arm. By measuring power here, Stages Power eliminates the complexity of filtering the power data from chain torques and the multiple vectors associated with spider based units or efficiency losses through the drivetrain. This measurement then derives total power using an algorithm that effectively doubles a rider’s left-measured power.
The most important factor of this whole discussion is the data. Please reference our comparative data tab.
Our Position:
90+ percent of riders out there need a real power number they can train to, NOT the ability to analyze their pedal stroke or left-right balance of power. (Note that the only, available, outdoor options to truly look at this data come from Look and Rotor)
The most important factor of this whole discussion is the data — the data doesn’t lie. Check out our comparisons tab.
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From pedaling force to power
To start with the basics, we need to look at how we derive power. We make a slight modification to a simple equation taught in Physics 101.
P=2∗((Fave∗9.8∗L)∗(R∗.1047))
Reading into this equation: P is power (Watts). The (2) is a multiplier and our one assumption, which represents the doubling of our left leg power measurement. We feel this assumption is fair and we’ve tested it to be consistent. This assumption is also the key factor that allows us to produce the Stages Power meter to be more compact, lighter, more robust, and more economical than any of the competition.
From there, the rest of the equation is standard physics. The average force per revolution (Fave) is measured by the strain gauges in kilograms and then converted to torque in Nm (Newton Meters) by multiplying it by the crank length (L) in meters and the gravitational constant (9.8m/s^2). Finally it is multiplied by the crank RPM which is converted to radians per second to derive the power.
Multiplying this equation by two gives us an overall power output based on both legs, and it’s through our own internal testing that we’ve found this assumption to be fair, consistent, and work for 99 percent of riders out there.
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The key to cadence
We have Apple and their fellow smart phone manufacturers to thank for our feature of accelerometer-based cadence. These phone manufacturers pioneered the use of accelerometers in smart phones to change the orientation of their display screens and facilitate other App features. Their use of the technology drove both development and more economical pricing making it a feasible technology for the Stages Power meter.
The most apparent benefit to an accelerometer-derived cadence is eliminating the need for any additional hardware outside of the power meter unit; thus the Stages Power meter does not need any additional wires, magnets or zip-ties.
The use of an accelerometer to measure cadence gives multiple position measurements per revolution, giving us enough data to know when a rider stops pedaling within the second they do so. The fast response and higher resolution allows us to build a better database of both power and cadence information.
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Self contained for fast install
Who wants to mess up the aesthetic of their beautiful bike by adding magnets or worse yet, zip-ties to their crank or chainstays. These methods are the mark of non-integrated aftermarket items not the innovative, forward thinking solution that a power savvy rider wants to add to their bike.
The Stages Power meter does not require any additional mounted hardware, save for the unit itself: no zip-ties, no magnets. For cadence, it uses an accelerometer that tracks crank position to calculate each rotation. The self-contained unit means installing the meter is as simple as replacing the non-drive crank arm, pairing the power meter to a compatible head unit, and heading out to pedal.
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A power meter for every disipline
The Stages Power meter is assembled to a variety of Shimano road and mountain cranks — from 105 to Dura-Ace 9000, as well as XT, XTR, Saint and DXR. There are also options for SRAM Rival road, X9 mountain, and Cannondale models, for road and mountain use.
While there is a Stages Power meter for every discipline, it is also offered at the lowest price of entry, US$699 (Shimano 105/SRAM Rival), in the industry. Both Shimano 105 and SRAM Rival models bring all of the features of the top Stages Power meters to riders who may not have ever before considered training with power.
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Comparative data
Ultimately our data answers this question, because no matter how you cut it - data doesn't lie.
Through extensive and thorough testing Stages Cycling prove the Stages Power meter's data to be both sound, and an extremely consistent measure for riders to train with.
We implore riders try the Stages Power meter and compare it to their experience with other power meters and weigh the costs and benefits. If they do this honestly, Stages Cycling believes any rider will become a Stages Power rider.
Competitor 1
Competitor 2
These two graphs are derived from a 100-minute snippet of a longer road ride. We've overlaid our data with a highly respected competitor's data (note: data was gathered concurrently) to illustrate our confidence in our power meter and algorithm. The top graph is derived from raw data, as it would export into analysis software, wereas the lower graph is averaged for better graphical assessment.
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New to Power
So you're new to the idea of power-based training, and likely, your first question is: why train with power?
To answer that question we must first start with an explanation of what measuring power in cycling does? It boils down to this: power is a true metric that remains relatively unaffected by temperature, wind speed, road surface, road grade, time of day, heart rate or any other outside parameter that might affect a cyclist's performance.
Since power is the most consistent measure we have of a cyclist's effort, it's the best metric to use when tracking a cyclist's training. Furthermore, power is the only measure that shows a true change in fitness or the performance of a cyclist over a period of time.
This is why power meters are universally accepted among coaches as the best tool available for training cyclists.
With power, and the knowledge of a good coach, web, or software training program, a cyclist can baseline, train, and track their efforts and expect the end result of improved performance.
Power can also provide the most accurate gauge of real time performance, thus a power meter can serve as a rider’s ‘rev’ limiter, ensuring that a rider puts forward their best performance and sustains it for the necessary time.
And this is simply what training with power can do for you. By training smarter with power you're guaranteed to get faster and be able to put the hurt on your competition.
The Stages Power meter offers an ease of implementation and low cost of entry to power training, which has never been available before. We have power meter models that cost as little as $699, and set up in less than 15 minutes (for left arm replacement) even for those with very little mechanical knowledge.
With every Stages Power meter we include a special package from Training Peaks to facilitate the education of those riders new to power measurement.
As part of this package, Stages Power meter owners will receive a complementary 1-month premium membership to Training Peaks and 1-month of tailored tips delivered daily via email from Joe Friel, expert cycling coach and author of the just released, Power Meter Handbook.
So if you're ready to get started with your own power-training program, look no further than the Stage Power meter models in the Stages Cycling web store or your local bicycle dealer.
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How can I find out if my bicycle is compatible with the Stages Power Meter?
To ensure your bike is compatible with the Stages Power Meter, we request you check these primary compatibility guidelines for your bike. Each of the following steps should guide you through the process of verifying that your bike is a good fit.
Frame Clearance
We recommend checking these in all instances due to the large number of variations of bicycle frames, parts spec, and ongoing model year changes that make it difficult to keep a running list. Checking the frame compatibility is simple and can be done with a 10mm allen wrench.
The diagram below provides the necessary “CLEARANCE ZONE” you should consider prior to making your crank purchase. As long as you have the necessary “clearance” between your crank arm and chain stay, and assuming you have existing compatible cranks, you should be able to utilize our solution with your crank set.This includes not just the chain stay of the bike, but also any chain stay mounted brake that sits in the space between the crank arm and the frame. For bikes with chain stay brakes, an alternate brake caliper may be required.
Chain Stay Brake
If you do note that your bike has a chain stay mounted brake that may interfere with the placement of the power meter on the left side, it may still be possible to use the Stages Power Meter. Please note the following info:
Brake model
Bike model and year
Crank model
Crank Compatibility
Once you've checked the frame for clearance, the next step is to confirm compatibility with your existing crank set. In some instances, a left crank option is not available, so a complete crank set may be required. Check our list of models to find an equivalent model with your existing crank. Check the product descriptions to confirm compatibility with other models of cranks from the same manufacturer, as an exact match is not always needed.
To help find your crank model, check the exterior of the crank for any printed brand and model information. The length of the crank is typically engraved or stamped into the back of each crank arm near the pedal spindle.
Crank Model Number and Length as seen on a Shimano 5800 left crank arm
Still need help?
If you're unsure if your existing crank set lines up with one of our models from Shimano, SRAM, FSA, or Cannondale - please make note of the brand, model, and bottom bracket type of your crank or snap some photos and contact us for more assistance