Does anyone have one of these fitted and FULLY understand it?

I just fitted a GSC10 to my XC bike, but I’m confused about the speed sensor.

On one hand it says that it’s all self calibrating because of the edge 800 GPS doing the speed… Does this mean I don’t need to worry about entering wheel sizes in the bike profiles pages (as this has switch to automatic)

Do I literally have to do nothing other than make sure the edge 800 recognises the GSC10?

Ultimately I don’t want to get to the end of a 40mile ride for the data to say it was a 20miles ride and my average speed was 14mph.

Any help much appreciated.

Some leave it some don’t
I entered the wheel circumference manually – it’s simple to do, why not?

I get the same distance on my commute (Garmin Edge 500) whether the magnet is attached to a spoke or if taken off so, no, you don’t need to bother entering wheel sizes.

I thought that, but then the magnet can be placed anywhere on the spoke so why does the wheel ciircumference make a different?

Also how do you calculate that with the tyre on too… I’m being thick I know

Mark your tyre and a mark on the floor at 6 o clock. Wheel the bike forward until the mark is at 6 o clock again and mark floor. Measure between the two marks on the floor.

MM

Also how do you calculate that with the tyre on too… I’m being thick I know

Line on the ground, roll bike one wheel revolution, measure distance. 26×2.1 is about 2070mm.

I thought that, but then the magnet can be placed anywhere on the spoke so why does the wheel ciircumference make a different?

Both ends of the spoke travel the same distance, so it’s just how far it has travelled between passing the sensor that matters.

I don’t have experience with the 800 but I have a 705 and I have a GSC10 on two of my bikes. With the 705 I pair the GSC10 with the GPS (only if its new or the battery has been replaced). As soon as the GSC10 senses the wheel or crank magnet it wakes up and a message pops up on the GPS screen.
I can set the 705 to auto calibrate or manual if I leave it in auto (I do) a message pops up on the screen after about 1/4 mile saying wheel size calibrated.
If the GPS doesn’t detect the GSC10 it’ll measure the mileage using the GPS.
If you really want a 40 mile ride to show as 20 miles just manually calibrate the wheel size to double what it should be 😀 (I’ve a feeling the GPS software might still overide if the error is large enough).

Yup, it only measures speed while the GPS is switched off (or on startup if you hit start before it’s fixed onto the satelites).

My Edge 305 died last night, ~£70 to get it fixed by Garmin or £160 for a Bryton Rider50? Anyone got one and know if cheep/free OS style mapping is available?

Yup, it only measures speed while the GPS is switched off

Really? lift your bike up and spin the wheel.

Biggest benefit for me was that the GPS knows you are still moving if it looses the satelite for a few seconds.
Without the speed sensor cycling under a bridge causes the speed to drop to zero then spike to 50mph as you magically appear on the other side of the bridge.
Weather I have the wheel size entered or the GPS set to auto the speed still is less stable than the wired cateye but the end of ride distances match pretty well

Without the speed sensor cycling under a bridge causes the speed to drop to zero then spike to 50mph as you magically appear on the other side of the bridge.

Really? I genuinely can’t remember which bike my sensor is on, I get cadence from my PowerTap which I swap between both road bikes and just rely on the GPS speed, I’ve never ever noticed speed fluctuations as you describe. I think it’s clever enough to assume you carry on at a constant velocity until such time as it regains signal, which realistically is unlikely to be more than a couple of minutes, even if you ride through a long tunnel.

I’ve never ever had mine drop out whilst riding that I’ve noticed.

I’ve thought about adding one but haven’t been bothered to date – again my cadence comes from my powermeter on road.

I have heard that for techy switchback style routes offroad the gps measures very short which makes sense – but then again distance of road is not much of a measure of anything as its so terrain and mud dependent that I’ve never really paid much attention to it.

I have heard that for techy switchback style routes offroad the gps measures very short which makes sense – but then again distance of road is not much of a measure of anything as its so state terrain and mud dependent that I’ve never really paid much attention to it.

Admittedly I don’t ride much of that, but there’s one notable trail near me with short switchbacks and you can clearly see them when you upload the route.

You do need to calibrate the sensor as 1 full rotation will vary distance covered depending on tyre profile. I tried my edge 800 without the magnet at first but hated the erratic speed changes and the slowness. On average the gps is only accurate to 10 metres hence why it displays a speed when you are standing still.

Also, once the edge detects the sensor it then stops using gps data for speed and distance so you must calibrate it to be able to rely on the data.

It’s very simple to do!

Without the speed sensor cycling under a bridge causes the speed to drop to zero then spike to 50mph as you magically appear on the other side of the bridge.

That doesn’t happen