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Polar power problems - how to fix ?
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Did my first ride with the power system of Polar this week-end, just to check if I had put it correclty on the bike, and it seemed to work fine on the small chain front ring, giving outputs of around 200 watts (against wind on the flat), but when shifting to the big front chain ring, then the power output dropped to about 140 watts, which is not what one would expect.

Any explanation for this, did I do something wrong when installing the whole thing ?

Thanks a lot for your explanations.

P.S. The bike shop that helped me installing it was doing this for the first time too.
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Re: Polar power problems - how to fix ? [Diabolo] [ In reply to ]
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In Reply To:
Did my first ride with the power system of Polar this week-end, just to check if I had put it correclty on the bike, and it seemed to work fine on the small chain front ring, giving outputs of around 200 watts (against wind on the flat), but when shifting to the big front chain ring, then the power output dropped to about 140 watts, which is not what one would expect.


You may not have done anything wrong, I have a computrainer which also displays power in watts.

In my experience I have the highest wattage reading when I am cycling "up hill" - on the "flat" when I am spinning (by my standards anyway) my watt reading is lower, even though I am going faster.

It is a long time since my physics classes, but I do not think that you would necessarily expect your watts to increase just because you are using a higher gear.

Wouldn't the same speed using a higher gear mean less watts, merely because of the effect the gear ?

When I am an on the flat, even though I am traveling faster my perceived exertion is less and so is my hr - so I am not surprised that my/your watts are less.

I may of course be writing absolute rubbish so I will wait and see what the scientists/engineers have to say.
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Re: Polar power problems - how to fix ? [pete_newing] [ In reply to ]
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Thanks Pete.

Most of the ride was on the flats. Shifting from small to big front chain ring on the flat, you would expect to have to work harder when on the big chain ring, especially when your cadence is about the same.

But then again, as you, I am not a scientist or expect on this. It just makes sense to me this way.
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Re: Polar power problems - how to fix ? [Diabolo] [ In reply to ]
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Firstly, my caveat: I've never used or seen an S710, so have no actual experience of it. However, from the wattage list at topica.com, there appear to be quite a few people who have problems when installing the S710, it needs to be done very carefully and preferably with another meter (i.e., SRM or Power Tap) on the bike to ensure that it's correct. Here are two links from people who've written up their results/experiences with the S710: http://external.nj.nec.com/homepages/sandiway/bike/feather/tt/s710/index.html
http://www.schererfamily.com/Joisey_Scherers/Chris/cycling/polar/polars710.htm

Secondly, on a practical level, under given environmental and topographical conditions at the same velocity, your power output will be the same irrespective of what gear you use (i.e., 42 x 21 or 53 x 11). Obviously, cadence would alter as would the force that you'd apply to the pedals.

Ric Stern

http://www.cyclecoach.com
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Re: Polar power problems - how to fix ? [Diabolo] [ In reply to ]
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"which is not what one would expect. "

Sorry to have to be the one to tell you this; all the reviews on the internet point to this very same problem.

In fact it is exactly what I expected. You can do some things to lessen the difference but you'll never get it to go away. That problem is the reason i don't have a power meter on my bike today. i own the 710 but when I found out about this problem I decided not to get the power unit. I ride a triple; all the reviews report this problem on double rings it would be much worse on a triple.

Hope you find a work around.
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