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Garmin 705 and PowerTap

William JenksWilliam Jenks
in General Training Discussions

I have the Garmin 705 and a wireless powertap wheel.

Today I noticed that I'm a firmware verstion behind.  I have 3.1 and there is (and has been) a 3.3.  There are a couple of nice-sounding features listed in the version history.  However, I also know there have been "lemon" firmware versions from time to time, especially regarding power recording.  So if it ain't broke....

Does anybody know the "wisdom" about Garmin 3.1 vs 3.3 firmwear on the Edge 705?  Thanks!

Comments

  • Cary BlancoCary Blanco
    William,

    I've been using 3.3 without any issues since it was released (knock on wood). There are reports of other people having problems in the Garmin forums. It looks like your A race is far enough away to give it a try. I believe it wipes your settings, so get a good look at what you've got on your data fileds etc.

    Worse comes to worst, I've got the 3.1 firmware that I can send you if you need to downgrade back.

    Good luck.
  • William JenksWilliam Jenks
    Thanks Cary. Will give it a go!
  • Michael ByertsMichael Byerts
    I just upgraded the firmware last week. My saturday ride went fine. But a race on Sunday, the 705 had issues. Power data recording was just fine, but speed and distance was way off. It claims the 30K course was less than 20K, and that my max speed on a downhill where I was in fact going more than 35 mph was about 18. Not sure why it misbehaved like that.
  • William JenksWilliam Jenks
    Sounds like a couple possibilities to check. (1) When the hub batteries start to fail, you get drop outs...which you might not notice on power, but the mileage would be wrong; (2) I think under certain circumstances the speed and distance are picked up from the magnet and cadence sensor (if you have one) instead of the GPS. If that got changed somehow and the wheel diameter is wrong, you would get the right power and wrong distance.

    Of course it could be one of the bad Garmin dropout problems too.... hope not!

    Wm
  • Cary BlancoCary Blanco
    Posted By Michael Byerts on 28 Jun 2011 05:51 PM

    I just upgraded the firmware last week. My saturday ride went fine. But a race on Sunday, the 705 had issues. Power data recording was just fine, but speed and distance was way off. It claims the 30K course was less than 20K, and that my max speed on a downhill where I was in fact going more than 35 mph was about 18. Not sure why it misbehaved like that.



    Friend had the same problem after the update. I believe he went to bike profile and unchecked cadence and power and all was good.

  • William JenksWilliam Jenks
    That's a strange thing to have to check... those derive from whether you have a power meter and whether you have the cadence pickup.

    It sounds like you're saying that you told the Garmin that you didn't have those things and then everything was fixed? Strange!

    I am going to do my first ride with the 3.3 firmware today. I haven't changed any of the settings from my 3.1 firmware, which (on the bike profile) have both the cadence and power checked and a custom wheel size. (2093 mm)

    I had set custom wheel size a while back when I kept getting notices that automatic wheel size calculations were being done and once in a while got odd speed/distances. That all stopped. Anyway, we'll see how it goes!
  • Cary BlancoCary Blanco
    If you've already paired your PM and cadence sensor and don't use more than one bike (profiles) then you don't need to check these boxes in bike profiles. This is only for people with different cadence sensors and/or PMs on different bikes. What people have seen is t crazy auto calculated wheel size that gives them incorrect speed and distance. If you've got a correct custom-wheel size in then you're fine, then problem occur with the auto wheel size setting.
  • Michael ByertsMichael Byerts
    Thanks! I will try changing that setting and see if it fixes the problem.
  • William JenksWilliam Jenks
    Got it. Thanks!
  • Cary BlancoCary Blanco
    William, let us know how your ride goes.
  • William JenksWilliam Jenks
    On my 705, if I unchecked the PM option under bike setup, the whole wheel circumfrence thing went away, so I left both that and the cadence sensor thing checked.

    I have the luxury of having a FR 310xt as well, and I took it along as a double check.

    Both instruments came out reading the same distance and average speed. There is a slight difference in the average power, but I use the 310xt on the bike so little, this may have something to do with autopausing or averaging zeros that I have lost track of. In any case, the difference is just 3 W, so it's clearly not a big deal. It appears that everything is hunky-dory.

    Incidentally, the total ascent is ridiculously high on the 310xt. According to Garmin Connect, total ascent is ~700 feet using 310xt and "elevation corrections". I get 1100 feet raw on the 705 and 2300 feet on the 310xt.

    Because the course has lots of very small "hills", I wouldn't be surprised if the 1100 figure is closer to correct than the 700 ft figure (given that they probably don't have data every 10 feet or whatever on the road), but it is interesting to see that the GPS and barometric methods give SUCH different values for climbing.

  • Cary BlancoCary Blanco
    William,

    Apparently I did not communicate effectively, my apologies.

    If you have speed/distance anomalies, it's probably due to a auto-wheel size not being calculated correctly, so you can specify a wheel size or bypass the auto-wheel size altogether by unchecking those boxes.

    So, IF you have speed/distance errors, THEN try unchecking those boxes, it will force the 705 to use GPS for speed and distance. IF you use a custom wheel size, THEN you should could check the boxes because you specifically know how to put the data in that is required by checking those boxes.
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