Power Up, pt 5: Kurt Kinetic

 May 7, 2012 article & images by Nick Salazar

Kurt Power
Training with power doesn't have to cost a fortune, if you're willing to train indoors.

Thus far, the Power Up series has focused on only one measurement device: the Quarq crankset. And while there are many other options on the market, they all share a fairly hefty price tag. Today we're going to look at one of the cheapest solutions there is, made by Kurt Kinetic. That's right, the company that primarily makes trainers has in its arsenal a bit of gear that calculates power based off of the trainer itself, or more specifically, how fast the flywheel is spinning.

So let me say that again. If you want to get into power on the cheap, all you need is a Kurt Kinetic trainer, and their $79 cyclometer. Of course, that means you have to be riding indoors to get power data, but there are pretty respectable riders who have no problem doing their training inside.

So how does it work? Kurt's fluid chamber is filled with a silicon solution that exhibits very predictable properties. It doesn't expand or change viscosity as it heats up, so its power curve can be very accurately calculated for a given range of loads. In fact, Kurt publishes the equation they derived for the trainers. The equation makes a couple of assumptions to narrow down the variables involved, such that all you have to plug into the equation is speed, and it will spit out power. How accurate is it? I found it to be very good, tracking my Quarq within a couple of percentage points. TrainerRoad did a more thorough analysis of its accuracy, and found basically the same thing that I did. One caveat is that changes in rolling resistance can have a measurable impact on accuracy, so make sure you crank the flywheel down to your tire with roughly the same amount of force. It's worth noting that Computrainer has a sensor to measure that force, so that you can get more repeatable results.

Now, if all that's required to derive power from these trainers is speed, then why do you need the computer? Well, because it has the equation built in - it will show you your power as you're riding. But the downside is that it will only show it to you live. There's no way to record and download the data for later analysis. Fortunately, there are other solutions available. As mentioned above, Kurt Kinetic very smartly published their power equation, and this opens the trainer up to more universal applications. TrainerRoad, mentioned above, is first and foremost a software package that lets you record your data straight to your computer via an ANT+ stick and a laptop. It's a pretty slick solution, and definitely worth a look. In fact, I'll be doing just that in Part 6 of this Power Up series.

Kurt Kinetic also has a couple more indoor-specific products that aren't directly-related to power, but are definitely germane to the topic of riding on a trainer, and worth a mention here. Hit the jump to read about Kurt's heavy-weight flywheel option, and their indoor-specific training tire.

Tags » kurtkinetic,  powerup,  software
  • The Kurt Kinetic power computers (available wired and wireless) provide wattage readings when riding on a Kurt trainer, and functions as a regular speed/cadence head unit when riding outdoors.
  • The Kurt Kinetic speed sensor is small and elegant.
  • The Kurt heart rate monitor isn't as fancy as some of the newer models from other brands, but it gets the job done.
  • Kurt Kinetic computers are bundled with a speed sensor and heart rate monitor, and start under $90 retail.
  • The massive Kurt Kinetic Pro Flywheel adds inertia to the trainer's resistance unit, making it harder to spin up and take longer to spin down - a little more like on the actual road.
  • The Pro Flywheel secures via a left-hand-thread thumbscrew. Since the trainer spins clockwise, the left hand threads prevent the flywheel from accidentally coming off while riding. Nice touch!
  • The Pro Flywheel sitting on the floor next to the Kurt Kinetic Rock and Roll trainer.
  • The Pro Flywheel mounts right on top of the existing flywheel
  • Kurt Kinetic also sells a trainer-specific tire, manufactured by Kenda.
  • I haven't tried it out yet, but it's reported to reduce trainer noise and the tire debris. Beware, the tire is reported to be a tight fit on some clincher beads.

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