Among the most talked about products at last fall’s Interbike tradeshow — the Stages Cycling Power Meter — is slated to start shipping to shops and consumers this week. If it can deliver on it’s significant promise, it could mark a huge sea change in the power meter market, substantially lowering the price and weight associated with strain gage-based power measuring systems.
Last week, the Boulder, Colorado-based company gathered about a dozen members of the cycling media to conduct initial test rides and go over final thoughts and figures relating to the new product. RoadBikeReview.com was on hand. Here are the highlights of what we learned.
What it is
In a nutshell, it’s a power measuring device manufactured in Colorado that’s affixed to the inside of a bike’s non-drive side crank arm, and uses strain gages to determine power output by measuring deflection (aka extremely subtle microscopic bending) of said crank under load. Each strain gage is specifically calibrated to the crank it’s mounted on.
The unit takes 64 discrete measures per second, which is far more than necessary for road riding, but could have interesting applications in the track, BMX and even downhill mountain biking world where rapid acceleration is key to success.
All that information is then doubled to account for the fact that it’s measuring just one leg, then transmitted to the receiving device of your choice (Garmin head unit, iPhone, etc.) via ANT+ or Bluetooth technology. There’s also an inboard accelerometer to measure speed and cadence.
It should be noted that Stages does not sell any of these recipient devices, just the non-drive side cranks with device affixed, or full cranksets with device. Also, the system only works with alloy cranks, which bend at a consistent rate, versus carbon with its mix of materials that do not bend uniformly.
That’s no problem for Shimano users who can choose from nine different cranks, including Dura-Ace 9000 and Saint. But SRAM Red or Force aficionados will have to drop down to Rival. This was the case with the RoadBikeReview.com test set-up. We had the SRAM Red 50×34 carbon compact set-up removed from our road bike, and replaced with a SRAM Rival set-up including the new power meter and a BB30 adapter made by Wheels Manufacturing. The net effect was a 154-gram weight penalty (from 624 grams to 778 grams).
Stages says it is currently working on a better BB30 solution, which will utilize Cannondale’s various BB30 cranks. But that wont be available until later in the spring at the earliest. You can see the full line-up of current offerings, including available lengths and colors here.
FSA and Campagnolo are not among the choices and from what we heard during the two-day press event, it doesn’t sound like that will change anytime soon.
According to Stages marketing man Matt Pacocha, the unit works with “about 90 percent of the road bike frames on the market. It just depends on the location of the rear brake. It can be an issue with some lower priced time trial bikes, which use a full-sized caliper on the chainstay.”
Stages does not retrofit its product on previously purchased crank arms, so don’t bother asking if you can stop by Boulder HQ with your old crank in tow. The answer is, no.
The unit is powered by a CR2032 battery, which will cost you about a dollar at the grocery store. Run time is claimed to be 200 hours, with accuracy pegged at +/- 2% when measured at 100 watts and 90rpm. Occasional free firmware updates will be delivered via Bluetooth by way of the Stages Cycling Utility App, which will be available soon.
The Stages cycling power meter also includes a built-in thermometer, which feeds info into the main calculation so temperature change does not effect accuracy.
Some may question the accuracy of measuring just one leg. But Stages did its best to dismiss this concern, bringing in well-regarded cycling coach Neal Henderson, who’s the sports science manager at the Boulder Center for Sports Medicine. Serving as an expert witness of sorts, Henderson said he rarely sees significant output differences between legs, and it’s usually with patients who have had a knee or hip replacement, or some other significant body change.
Henderson also said he’d been doing some testing with the Stages Power meter and liked what he saw, writing on Twitter, “I’m impressed with @stagescycling so far. Simple use, very light weight, consistent data, & very close to other validated PMs.” You can read more of what Coach Neal had to say on his Twitter stream and see links to his various power files.
Price & Weight
Prices on the Stages Cycling power meter start at $700 (SRAM Rival, SRAM X9) and climb to $900 for Shimano Dura-Ace, XTR and Saint. The Cannondale Hollowgram models will run $50 to $100 more than Dura-Ace when they become available in the spring.
The power meter can be purchased via the Stages Cycling website, or at select independent bike shops. Purchase price also includes a 1-month premium subscription to both TrainingPeaks and Strava, roughly a $26 value.
By comparison, the least expensive PowerTap model runs $899, but that’s just for the hub. You still need to build up a wheel, which you will then be locked into if you want to ride/train/race with power. SRM and Quarq don’t restrict wheel choice, but the least expensive model is the recently-introduced Quarq RIKEN, which retails for about $1600. Prices of SRM and Quarq quickly rise into the $2000 range.
We didn’t actually get a chance to weigh one of the Stages units ourselves, but claimed weight is “under 20 grams” and senior VP Pat Warner said that most units are closer to 14 grams. The weight hit for PowerTap models is in the 100-gram range, while spider-based systems typically add around 30 grams.
The variance in weight for the Stages system is due to the difference in protective housing shape from one crank model to the next. This housing is bonded onto the crank using a proprietary method that Stages claims does no damage to the crank itself, and creates a bond so strong that the two pieces effectively become one. That means it’s totally waterproof, though Stages warns that it should not be directly sprayed with a pressure washer so cross racers need to be careful.
Each power meter comes with a one year warranty, and a longer warranty (think Apple Care) can be purchased for $105 to $135 depending on the model you choose. This could be a wise choice for mountain bikers and cyclocross racers, who run a much greater risk of suffering a direct-impact rock strike or crashing.