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  1. #1
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    Edge 705 speed sensor question(s)

    Been using my 705 for a couple of weeks and all was well. I really like it and purchased an optional micro SD card to give me the local country roads. However, today I installed the optional cadence sensor and went for a ride. The auto pause kept kicking in because the speed would drop to zero while I was cruising along at 18 mph. Then the auto resume would come back on. Very annoying.

    #1.) Is the speed dropping to zero because it's not sensing my magnet on the spokes or is there another solution ? The cadence would keep reading out, but the speed would go to zero.

    Also, I would rather my 705 determine speed from the satellite as it did before I installed the cadence unit. I simply want to know what my cadence is and don't really want my spokes to tell what my speed is. When I selected auto calibrate for my wheel size, it determined an odd number for my wheel (2089) instead of the usual (2124) as I've used for a 700 wheel with all of my other bike computers. While riding today I felt as if the speed was off from what I normally ride.

    #2.) Is there a way of having the cadence and not using the spoke magnet for determining speed ? I'd rather rely on the GPS for my speed.

    #3.) How do I determine the proper wheel size to input into my 705 without having it auto select my wheel size ?

    So far, I really like my 705.

    Thanks in advance for any help.

  2. #2
    Hack Racer
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    Your questions are confusing... It would help if you clarified your questions a bit. Based on what I've read...

    1.) Speed on the edge 705 and edge 305 is calculated using the GPS by figuring out the time elasped between distances. The only time the garmin units uses the spoke magnet is when either of two things happen: A.) You do not have satellite lock (because you in a concrete jungle downtown urban area) or B.) You are using an indoor trainer where the wheel is spinning but you are not physically moving. The auto calibrate takes into account the small variances in tires and the pressure I think. That is why you get a slightly odd number.

    2.) I don't understand this question. Cadence is not a function of the spoke magnet. Cadence is determined by how fast your crank arms are rotating (revolutions per minute) by measuring the time it takes for the magnet on the crank arm to make one full revolution. Make sure you have the correct gap between the sensor and the magnet and the for and aft position of the sensor and the magnet is crucial. The instructions on the garmin CD explain it very clearly. So does the pdf file of the instruction manual which you can download from the garmin site.

    3.) To determine wheel size. You fully inflate your tire. Line up the valve stem so it's perfectly perpendicular to the ground and mark this spot. roll your bike forward until the valve stem completes one complete rotation and again is perpendicular to the ground. Mark this spot on teh ground. Measure the distance between the two marking in millimeters and you will have the circumference of the tire/wheel. Make sure the line is straight (as you roll the bike).

  3. #3
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    I'll try to make more sense of what I'm getting at.


    #1.) Is the speed dropping to zero because it's not sensing my magnet on the spokes or is there another solution ? The cadence would keep reading out, but the speed would go to zero.

    1.) Speed on the edge 705 and edge 305 is calculated using the GPS by figuring out the time elasped between distances. The only time the garmin units uses the spoke magnet is when either of two things happen: A.) You do not have satellite lock (because you in a concrete jungle downtown urban area) B.) You are using an indoor trainer where the wheel is spinning but you are not physically moving.

    This doesn't make any sense as my unit worked perfectly until I installed the spoke magnet. I'm riding out in the open country where I shouldn't have any problems with satellite reception. Neither of these solutions apply in my case.

    #2.) Is there a way of having the cadence and not using the spoke magnet for determining speed ? I'd rather rely on the GPS for my speed.

    2.) I don't understand this question. Cadence is not a function of the spoke magnet.

    My question isn't about the cadence at all but rather with the spoke magnet and if I can get rid of the spoke magnet. I just want to use the GPS for determining my speed. Do I have to have both sensors, the pedal and spoke, hooked up in order for the GSC 10 to work ?

    Sorry if my question seemed confusing

  4. #4
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    I have heard this before about the sensor not overriding the GPS for speed. I think that I would disagree on that. The reason that being when I have my bike in the stand, with the unit on a receiving signal from many satellites, I spin my tire and I get a speed reading on the unit. I think that the 705 bypasses the GPS for speed when it senses the cadence sensor. I also had a defective sensor which only read speed part of the time and I took a ride which is 22 miles and I came up with about 12 miles. By the way, the bad sensor was replaced my Garmin with no questions asked, no receipt, no return of the old product, nothing. I was impressed as I could be.

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