The Garmin Speed/Cadence sensor (GSC 10) is Garmin’s basic ANT+ way of getting speed and cadence data from wheels and pedals to your ANT+ device. Much has been made recently about the Garmin Magnetless Cadence Sensor that was reviewed here on TriedOnline a few weeks ago. During these winter months I probably join a number of other people in getting the majority of my bike miles in on a turbo trainer, and I needed to be able to measure cadence and speed, as I was not able to take this information off a GPS track. Enter the GSC 10.
Now the immediate question is why choose this over the magnetless options? Put simply, there are two reasons. Firstly the full magnetless setup is about £20 more expensive, to provide you with exactly the same data. Secondly, my current riding setup involves switching wheels between bikes, rather than switching bikes, and it is easier to transfer one spoke magnet between wheels, than it is to switch two units over between bikes. This is not to say that magnetless might not be the correct choice for many people, especially if one switches between bikes a lot as the GSC 10 is pretty much a permanent fixture on the frame it is installed on, and also would require a fairly endless supply of cable ties if one were to switch it over every other ride. Many readers will be very familiar with the GSC 10 and other speed/cadence sensors like it (such as the Wahoo Blue) and it is clearly a tried and tested design for capturing this sort of data.
Opening the Box
As you might expect from Garmin, the GSC 10 comes very well packaged in a sturdy laminated cardboard box, and there was a reassuring amount of bubblewrap around the sensor itself. Most of the contents of the box are laid out in the picture below (we have missed out the instruction manuals and cable ties) and as you can see there is the sensor itself, two magnets – one for spoke and one for crank – and two rubber mounting spacers so that whatever your frame type you can achieve a snug fit. Garmin also supply plenty of cable ties for attaching the speed cadence sensor and the crank magnet.
The instructions for installation are well laid out, in the usual variety of languages, and easy to follow. The first stage is attaching the crank magnet. This HAS to be first as the position of this component dictates where on the frame the main unit is mounted. In the picture below you can see the simple yet effective method of attachment. The magnet has a peel off back and so sticks to the crank to aid positioning, and the cable tie in the groove locks the whole thing in place. This picture shows the magnet mounted to a slightly older style of Shimano crank.
A minor inconvenience is shown in the right hand picture. My bike has Vision TTi Max cranks, and these have a significant cutout on the back of them, as can be seen in the top image of the drive side crank. This meant the cable tie could not secure the magnet properly, and the sticker is never going to be strong enough to hold it on. The solution that I came up with was to cut a small amount (about 1cm) off a foam nail file, and tape it into the cutout, so that the magnet can be firmly secured. To be on the safe side I then taped over the whole assembly, just for security, shown in the bottom half of the image. I expect that the Magnetless cadence sensor’s ‘tri-rubber-band’ attachment system would work much better on my cranks.
Next comes the installation of the Garmin Speed Cadence sensor itself. First one chooses the rubber mounting spacer that best fits the area of the rear frame that the sensor is to go on. There is a sticky pad on top of the spacer for more security. The sensor has to be aligned so that the crank magnet passes next to the small line marked on the outer side of the sensor. The cable ties are then passed through the holes and secured around the frame.
Next, the moveable armature is set up to record the speed from your back wheel. Seen in these pictures in the ‘down’ position, it can also be moved upwards if there is not enough clearance between the frame and the spokes. The magnet is then mounted on the spokes to align with the mark on the bar of the sensor. This whole setup process probably takes longer to describe than actually execute, but as mentioned above it is very much a semi-permanent option, and for a slightly higher investment the Magnetless sensors (both cadence and speed) can be transferred between bikes in a matter of seconds.
To check it’s all working correctly, the white circular button (see image above) can be activated which will illuminate red each time the crank magnet passes and green for the spoke magnet. This is also handy if you ever need to check if the battery has died.
Once set up it is but the work of a moment to get the GSC 10 paired up with the ANT+ enabled device of your choice. I paired it with the Garmin Forerunner 920XT, already extensively reviewed right here on TriedOnline. All one needs to do is turn the pedals with the 920XT set to search for sensors and it is connected immediately. Once you have hit OK on the watch this will be remembered for future occasions and will automatically hook up whenever the pedals are turning.
Functions & Accuracy
The above screenshot of an activity on Garmin Connect was taken on an hour long turbo trainer session. As you can see the sensor is very accurate, capturing even small changes in cadence and ‘speed’. You can see 35 minutes into the ride I did a higher cadence section, after a longer period of sustained effort. When I get a chance I am going to run a test of the sensor against GPS tracked speed on a real ride, rather than a simulated one.
I get on really well with this bit of kit. It is a no-frills solution to both indoor training and on the go cadence, all in one well priced package. If you just use the one bike it is absolutely ideal, even with different wheelsets, as spoke magnets are a doddle to swap over. I did some research about the history of this sensor and it looks like the first iteration of it was in 2001, and it has remained virtually UNCHANGED FOR OVER A DECADE! I’m sure that there has been the odd software tweak but one of the things that I really like about this product is Garmin’s no-nonsense ‘if it ain’t broke don’t fix it’ approach. The competition from the magnetless options is high, and the sensor is ANT+ only, so it is a no-go for any Bluetooth only users, but I remain convinced that we have not seen the last of the GSC 10, and it will remain the first choice for many of us for a few more years to come.
We want the TriedOnline reviews to be as independent as possible. On that basis, a link to Amazon should provide the most impartial method of you looking at other user comments should you be considering a purchase. You can also find the product info direct at Garmin