Garmin GSC 10 Speed/Cadence Bike Sensor

Review by Brad Jackson for Garmin GSC 10 Speed/Cadence Bike Sensor
Rating:
Another handy piece of equipment from Garmin!

This kit comes in three basic parts; a sensor unit, which is about the size of a matchbox, and two magnets about the size of your pinky nail. Several zip-ties are included for mounting purposes; the entire kit weighs at most a couple of ounces.

Installation is pretty straightforward, but do follow the directions carefully and don’t snug down the zip-ties until you’re sure you’ve got all three components just where you want them and have tested the system!

The sensor mounts to the left chain stay with a pair of zip-ties. Garmin thoughtfully added a piece of rubber padding to the bottom of the sensor unit, so it won’t rough up your fancy carbon frame or your paint job

A single zip-tie attaches the crank magnet to the crank, although I had to use a large (3/4″) shim on my FSA crank (which has a curved profile and a hollow back) to place the crank magnet in the proper position for the sensor to “see” it. The spoke magnet clamp has both a round hole and a square hole; make sure you use the right hole for your spoke profile! I mounted mine on a spoke directly opposite the tire valve, just to help keep the wheel in balance.

The sensor unit must be positioned along the chain stay such that it can “see” both the crank magnet as it passes by the cadence sensor (the round part on the side of the sensor unit), and the spoke magnet as it passes the speed sensor (the part that looks like a lever in the picture).

Testing is accomplished by pressing a small button on the sensor unit, which prompts it to flash a red LED, then a green one to indicate that testing is started. As pointed out by another reviewer, the LEDs are hard to see in bright ambient light; I’d recommend testing in a garage if possible. Hi-intensity LEDs would have solved this problem, although I suspect these LEDs were chosen for their low power consumption, so maybe it’s a smart design decision after all.

Once the test button is pressed, the next 60 revolutions of the crank should cause the red LED to flash when the crank magnet passes the sensor, while the spoke magnet passing the sensor should generate a green LED flash. If you saw the red/green flash when the button was pressed, but don’t see a flash as each magnet passes the sensor, chances are one or both magnets are not properly aligned with the sensor (there are alignment lines on the sensor and both magnets), or the magnets are passing too far from the sensor (this is the problem I encountered and solved with a shim).

When you’re sure everything is in the right places, snug the zip-ties and cut them flush. Then set up a screen (typically the Biking screen) on your 305 to display Cadence in one of the data fields, and go ride!

Review by Ron Henson for Garmin GSC 10 Speed/Cadence Bike Sensor
Rating:
The design could be improved upon as you need to have a magnet on both the crank arm and the spoke within 5mm of the sensor. This makes id difficult and may require some minor modifications on some bicycles (I needed to add a spacer between the crank arm and the magnet). Too much tilt towards the crank, risks having the arm of the sensor being caught in the spokes after a large bump on the trails or raod. I have known of other people being able to purchase a larger magnet to the inside of the pedal screw which allows the sensor to be farther appart. Other than that, it works great with the Edge.

Review by Thomas L. Wilson Jr. for Garmin GSC 10 Speed/Cadence Bike Sensor
Rating:
Easy installation of sensor and magnets. Crank magnet come loose easily.

Pairing the sensor with the receiver unit can fail without much of an indication of the problem. Once the sensor is paired, the unit works very reliably.