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Garmin Hub-based Speed Sensor for Fatbiking

For years I’ve advocated for the use of a wheel speed sensor to augment the data of GPS-based bike computers in order to alleviate distance issues caused by aliasing. Up until recently the only good options for this were traditional magnet-and-reed-switch units like the Garmin GSC-10 Speed/Cadence Bike Sensor and the Wahoo Cycling ANT+ Speeed/Cadence Sensor. These sensors work well in general, but I’ve had issues with them on my fatbike.

Because of  snow buildup on the rim (photo) the sensor is positioned closer to the hub (photo) to keep it from scraping in the snow. Withof the further-back position near my heel and the frequency of falling over when when riding in snow, it’s not uncommon for the sensor to get knocked around and tilted slightly inward. This causes the reed switch arm of the sensor to knock against spokes: the usual tick-tick-tick sound. It seems that these repeated, gentle physical impacts break the switch, as I’ve now had two which stop picking up wheel speed after a year or so on my fatbike. The rearward positioning also makes it impossible to use the cadence side, which feels a bit wasteful.

Garmin recently released a new series of speed/cadence sensors which use internal motion sensors instead of magnets (sensor bundle page on Garmin’s site). These were reviewed in great detail over here by DC Rainmaker, and the hub-based speed sensor seemed a perfect fit for my fatbike. This design will stay away from both the snow and my heels, and lacking a reed switch there isn’t that part to fail. The lack of cadence sensing on a fatbike is fine with me, as it is used in such mixed conditions such data isn’t very useful. When cleaning up my fatbike earlier this week I ordered the standalone speed sensor ($39.99 from Amazon) and fitted it last night before heading out for a ride.

My first impressions are very positive. It connected to my Garmin Edge 510 just as I’d expect, and a ride through River Bends parking lot automatically calibrated it to a sane number. A 1.5 hour trail ride near dark went fine with it, and it just seemed to work, similar in function to the GSC-10, but with a technical implementation that is more suited to fatbiking. I’ll stick with the traditional reed switch sensors for my other bikes, as I haven’t had the same kind of difficulty there and I don’t strap-to-crank-arm sensors, but for here on the Mukluk, it seems a good fit.

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