Garmin cadence Sensor question

subscriber

Just fitted the Garmin GSC 10 cadence sensor there few days ago. Just a quick question about it. I have only used it on the turbo trainer so far on "indoor mode" with my 305, and it allows me to gauge speed as well as cadence. So when I bring it outdoors in "outdoor mode", is it going to be gauging my speed based on the cadence sensor or based on my 305's GPS system. I would imagine the GPS is more accurate for speed so was just wondering if I am loosing out on speed accuracy with the cadence sensor installed????

Thanks
Subscriber

sconhome

If you have set up your wheel size the sensor is going to be more accurate than GPS.

Not sure about how Gamrin prioritises the information but if Polar detects a speed sensor it will always use the sensor for speed / distance and the GPS for mapping.

subscriber

amphkingwest wrote: »

If you have set up your wheel size the sensor is going to be more accurate than GPS.

Not sure about how Gamrin prioritises the information but if Polar detects a speed sensor it will always use the sensor for speed / distance and the GPS for mapping.

Thanks AKW, if my wheel takes a 700 x 23 tyre, will I program my 305 as 700 x 23 or will it be slightly larger than that, as in the actual rim size? I know it's programmed in mm to be accurate so a 700 x 23 will be 2097mm.

BTH

It will pick up speed and distance from the sensor above the gps. Simple fix, take the magnet off your wheel when riding outdoors.

sconhome

subscriber wrote: »

Thanks AKW, if my wheel takes a 700 x 23 tyre, will I program my 305 as 700 x 23 or will it be slightly larger than that, as in the actual rim size? I know it's programmed in mm to be accurate so a 700 x 23 will be 2097mm.

No its the tyre size that's important.

There is website somewhere that gives you the accurate circumference of the wheel based on the tyre. 2097 -2100mm sounds right for most.

I would argue against taking the magnet out (apart from losing the thing) the GPS can be 10% out and you won't get more accurate than a wheel based measurement. You don't use trust a GPS to measure how far you are driving or how fast you are going in a car (?)

Found calc: http://www.bikecalc.com/wheel_size_math

Amprodude

How does one set this cadence sensor correctly that it is accurately measuring distance? I went for a cycle yesterday and my Garmin read 50.0 km. my bike odometer read 50.3km and strava on my smartphone said 50.4. I just took the average of 3 to get my total distance.