I got a new cycling computer about a month ago, but the wireless speed and cadence sensor have already gone flat. My previous computer was old and used a wired sensor with magnets on the wheel and crankarm. Is this a normal lifespan for the new units that don’t use magnets, or is there something else I can try?

I have gotten a few e-mails about the GPS computer’s accuracy in heavy tree cover, and the answer is to add one of these Bluetooth or ANT+ wireless sensors. They use an internal gyro to automatically determine wheel size and are surprisingly accurate. Their real downside is that they turn on with movement. This might sound convenient, and it is in normal conditions, but they power on from any movement. Since they don’t use a magnet to determine a full rotation, any movement powers them on.

If you transport your bike in a vehicle this can cause the unit to power on and stay on for the entire drive. If you do this often enough, then it will cause a noticeable amount of power drain. This affects cadence and speed sensors, as well as some power meters. I have even heard of SRAM’s eTap being affected, but from our experience, this has not been an issue.

I would recommend trying some new name-brand batteries as many times, because the supplied batteries are cheap. If the problem persists, reach out to the manufacturer and see what they say, but we get about 300–500 hours from our units. Also, remember that most computers will pair with any speed or cadence sensor. It doesn’t need to be brand-matching, and a different brand might offer a sensor that will fit your needs better than the one your computer’s brand offers.

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