Too bad it only measures left leg power. Most people's power distribution varies greaty over the course of a race, as fatigue sets in. Also, there have been numerous reports of inconsistent power readings from these meters, even while being used on rollers or a trainer. If a unit isn't at least self consistent... it's worthless as a training tool. Also, many people have found problems in how the units measure cadence (no magnets used, it's dependent upon accelerometers). It's easy to tell that if even small errors arise in cadence calculation, lots of problems can arise in the power numbers.
Stages Cycling: A Power Meter Perfect Ideal for Cyclocross? – Sea Otter 2013
If you’ve ever toyed with the idea of racing cyclocross with a PowerTap to get some solid wattage readings, then the Stages Power Meter might be a new toy to add to your wish list, especially if your PowerTap is on a clincher wheel and you’ve got a nice pair of tubular race wheels. The fully sealed Stages Cycling unit only adds 20 grams to your bike’s total weight, and it connects directly to a crankarm. The company offers different left crankarm options, including SRAM and Shimano, both in road and mountain bike models.
“The idea was that we wanted to introduce a power meter that was cost competitive so we wanted to make it under $1,000, which we did, and we also wanted to make something that was light,” Stages Cycling said. “The sensors only add 15-20 grams to the crank arm, and that’s including the battery. So it’s really light.”
“The main objective was cost and weight and also ease of installation. There are no magnets that need to go on the bike or anything, it goes on, easy to calibrate and then you go ride,” their rep adds.
How is it so light? “The compromise is that it measures left leg power only under the assumption that people are fairly symmetric, left-right, and we double that power,” he explains.
Another interesting feature is that the sensor is wireless: “We send our power data out via ANT and we also do Bluetooth, there are several iPhone apps, so you’re kind of future-proof. Bluetooth also gives us the ability to do firmware updates so you can use the iPhone app and it’ll allow you to update as we add features. You don’t’ have to send it back, it’s something you can do in your garage and keep it moving.”
With the sensor, you get the power measurement and also can see your cadence.
So how will this work for cyclocross, and what can you learn? “I’ve been riding one for ‘cross for the past year,” he explains. “’Cross as everyone knows is a bunch of hard efforts, it’s on and off, on and off. And at the end of the race, your power averages out to be about like a hard road ride, but how you develop that power is completely different. It makes you think about your training and you realize you need to do more interval training.”
Stages Cycling Power Meters:
MSRP: $699 to $999, depending on model
Options: MTB and road cranks from Shimano and SRAM, but “For most applications, we can find some sort of crank that works with what your setup is and get power on it.”
More Info: Stages Cycling
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