Advantage of speed sensor?

I'd guess that most people want to know their speed/distance on an indoor trainer. The speed sensor gives you that. And it's pretty much mandatory for Zwift (for those so inclined).

That's easy to know, and there's no need for a sensor. On a trainer, speed and distance are both zero. Metrics like power, cadence, heart rate, those all make sense and are useful. Not speed and distance. (I'll grant you, if a VR trainer like a Zwift can actually mimic the actual feel and resistance forces of the road, then maybe speed makes sense. Otherwise, it's just a made up number.)

Taking speed from speed sensor but still recording GPS

I want to use speed sensor as MAIN source of speed in my 520 combined with GPS just for tracking, is it possible? I think 510 has this feature.

E.g. there are tunnels near my area where my GPS shows under 15kph speed but I really want to see exact speed, also in downhills or climbs where the GPS jumping.

Any ideas??

The 520 does that. Displayed speed and distance come from the sensor. The recorded data points in the FiT file contain the speed and accumulated distance derived from the sensor along with the GPS location. Post processing apps can use the Edge recorded distance or calculate speed and distance using the recorded locations and time of day stamp.

Thanks Tiger,

of course it could be, but not 520 of mine. It drops the speed rapidly in the tunnel with speed sensor connected and GPS+Glonass setup.

Are you sure the speed sensor is connected and working? If you spin the wheel does speed show? The 520 works just like the 510 so it appears to me that your 520 is not using the sensor at all

Yeah, but since your speed is zero, so is a speed sensor. Using one only makes any sense at all if you're riding rollers, and even there the opposing forces you feel on the road just aren't there. Speed is a useless metric indoors.

There is a difference between "Not as useful as it is outdoors" and "useless". For a variety of reasons many riders still find it useful to track their indoor mileage, even if it the effort doesn't correlate 100% with outdoor effort. Among other things, it helps to track service intervals during the winter or other times you're putting wear and tear on components without putting wear and tear on the road.

As mentioned previously, the three times a speed sensor is useful with GPS are:
1) When tree cover, tunnels, or other conditions block sat reception.
2) Short, convoluted routes where GPS sampling rates might produce errors.
3) Indoor/trainer/roller/virtual riding where there GPS does not produce data.

None of these make a speed sensor necessary, per se, but for a few bucks and grams, its worth having, IMHO.

BB

I can always tell if thee is something wrong with a speed sensor as the speed seems to fluctuate quite a bit when using GPS, well it did with my 500 and 510 anyway.

should the speed sensor be installed on the front or the rear hub?

should the speed sensor be installed on the front or the rear hub?

However you like, I've used it both on rear and front, it worked in both cases.

should the speed sensor be installed on the front or the rear hub?

In theory it shouldn't matter, unless of course you are using an indoor trainer then it HAS to go on the rear wheel.
It would be a case of try it and see though. If you have any problems, have a read through the speed/ cadence section of this forum, a lot of people seem to have problems with it on the rear, whether that be a distance / line of sight thing from the head unit, or a popular theory seems to be that there can be some magnetism in the drive train that throws the sensor off (it works by recognising the earths magnetic field as it rotates). I have the GSC10 so can't comment on any experience with the magnetless ones myself.