While power meters are amazing training tools that simplify the complexities of cadence and torque into the wattage figure on your head unit, they’re not magic and still rely on their human operators...
Once equipment for professionals only, thanks to Stages power meters have become much more easily accessible to a wide array of riders with differing levels of experience in the sport. With that reach, some regular misconceptions about how power meters work have cropped up and persisted, causing heartache for owners.
Here are some our customer service team hears on a regular basis. Take heed, and you’ll soon be a power meter expert – or at least likely to escape the trappings of the power meter newbie.
Comparability between meters
There are a variety of power meters on the market, each with different mechanics to achieve the same goal of reliable power measurement, but that doesn’t mean each will give you exactly the same data when used interchangeably. In turn, it doesn’t mean either is broken. For example, a power meter measuring at the crank is likely to be different from one measured at the hub or pedal, while stationary trainers that have a power readout often use an algorithm rather than strain gauges, making comparison tricky.
Different bikes, different power
Just as power meters aren’t quite created equal, neither are bikes themselves. Some new to power swap their power meter across more than one bike and baulk when the results differ. The stiffness of a bike’s bottom bracket can make significant difference to the way a crank-based power meter responds – as can geometry, tyre width, tyre pressures, gear ratios and even how clean your chain is. In short, there are a lot of variables! Neither bike’s readings are wrong; just don’t expect them to be the same. Oh, and don’t forget to perform a zero offset calibration every time you switch your head unit between different power meters.
Different athletes, different power
We’ve heard this one more times than we’d care to mention, but even if your friend is on the same kind of bike, with the same power meter, and you ride the same speed on the same course, your data will be different. You might have a different bike set-up, you’re probably different weights and conditions vary from second to second. And don’t be disheartened if your riding buddy is pushing more watts than you for the same speed – that means you’re winning! So relax; chances are that your power meter’s fine.
Same route, different power
While a power meter is great to spot training trends and improvements over time, the likelihood of producing consistent values over the same course day to day is extremely remote. What your power meter is doing is giving you accurate data for the conditions on that day, taking into account tyre pressures, tyre profile wear, changeable winds, rain, moisture on road surfaces, clothing choice, fatigue, whether your body is fighting a cold you don’t know about yet, bearings that are wearing out, dry chains, spending more time on the drops as you get fitter, drafting other riders and vehicles… These are all reasons for varying power data – even if your commute home takes the exact same 45 minutes!
Position changes everything
Another regular query we hear is regarding different power figures on TT or mountain bikes. Riding position makes a huge difference to the bike’s engine (that’s you) and its ability to push the pedals. Don’t rely on data from one position to be accurate for another, especially when transitioning from an upright riding position to an aggressive time trial set-up. If you’re riding different bikes, perform an FTP test on each to get a rough differential comparison between each and ensure you’re training at your best.
If there’s one tip that helps people out of a lot of connection issues, it’s to bypass the ‘search’ function on your head unit, especially if there are other power meters around. Every power meter has its identification number listed on the unit, so type this into the serial number field instead to be sure of a reliable connection to the right device. Also, be sure that the software on both power meter and your head unit is up to date – so many problems disappear after a firmware update.
If you’re using a Stages Shimano power meter, be aware that using the correct and symmetrically applied torque value when tightening the pinch bolts, along with correct bearing preload, is hugely important to valid and consistent data, as well as BB bearing life. Keep an eye on your BB too – notchy bearings in need of replacement will certainly affect data.
Dropouts aren’t always dropouts
You do a hard ride, get home and see loads of zeroes in your data. Your power meter must be acting up right? This is one we hear all the time – and it’s usually not down to faulty hardware, but due to the fact that whenever you stop pedalling, your wattage hits zero. The same is true if you don’t use auto pause and stop at traffic lights. A good way to check is to compare a graph of your power data with elevation data. See dropouts on the downhills? Sounds right to us! It sounds stupid, but if we had an extra watt for every call we had, we’d be winning Le Tour!
Power meters read low on indoor trainers
This is a very curious phenomenon that happens to nearly all riders. Bereft of the mental stimulation and cooling effect of the rushing air that we enjoy while riding on the road, it’s harder to hit big power numbers on indoor trainers. So if you’re using indoor test results to inform outdoor training, add a pinch of salt. Using a fan while training indoors can help you achieve better results. If you perform an FTP test on the road and indoors, you may be able to see a consistent indoor-outdoor difference.
Power changes as you do
One of the strangest queries we receive is users worrying about power numbers rising over time as they use their power meter. Unless you’ve been riding less since installing your power meter, the likelihood is that you’re actually just getting fitter. At the other end of the spectrum, there still seem to be people who think a power meter will automatically make you faster and add power to your legs. Don’t be that mechanical dope in your local bike shop!