Happy Polar 720 Power Owners?



bob_chew

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Oct 14, 2003
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I am struggling between Powertap and Polar 720 with Power. I have read all the tests and I think I have a grip on pros and cons of each system. Given all my research I am close to getting the 720 with power because of the price difference (the polar power option is about a third the price of powertap pro) but I must say that I haven't read too many comments from people who own the Polar power device and LOVE it. Most comments are complaints about installation or limitations on capturing low power readings etc.

Anyone out there LOVE their Polar power meter?

thx
 

ART

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Jun 24, 2003
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Originally posted by bob_chew
I am struggling between Powertap and Polar 720 with Power. I have read all the tests and I think I have a grip on pros and cons of each system. Given all my research I am close to getting the 720 with power because of the price difference (the polar power option is about a third the price of powertap pro) but I must say that I haven't read too many comments from people who own the Polar power device and LOVE it. Most comments are complaints about installation or limitations on capturing low power readings etc.

Anyone out there LOVE their Polar power meter?

thx

I have had abysmal results with the polar power option. Very inconsistent readings after many controlled tests. The results often make no sense whatsoever and the readouts are dramatically different then the power readings on my Computrainer which I know is very accurate. The unit is hard to install and creates some very annoying issues. For example, to have the chain tension sesor within the appropriate distance from the chain, the power of the sensors magnet causes the chain to pull down onto the sensor if you stop pedaling- upon commencement of pedaling the chain does not line up properly with the chain ring it is on causing it to rub on the front deurallier or worse causing the chain to come off. God forbid you backpedal- the chain gets all bunched up.

Additionally, I have received horrible feedback from Polar regarding these problems. I have used (happilly I might add) Polar HR watches for close to 20 yrs now and was shocked at this product and Polars non-responsive feedback I have been very very disappointed.
 

tsai

New Member
Dec 2, 2003
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i have a 520, which has the cadence function - but not the power option of the 720). the cadence function doesnt work very well - very intermittent, and essentially useless if you plan to keep the watch unit on your wrist, especially when on aerobars, etc.
 

peterwright

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Mar 5, 2003
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I have had the power option of the 720 on my race bike for about 6 months and have to say that it is not great. I have it fitted correctly but find that it is very easy to knock one of the sensors and suddenly find you have no cadence or speed. Power readings seem a little inconsistent and also low compared to other references I have. On balance I would spend more and get a better product. I have just changed to an Ergomo and it looks to be a solid product.

Peter
 

beerco

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Nov 8, 2003
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Originally posted by bob_chew
I am struggling between Powertap and Polar 720 with Power. I have read all the tests and I think I have a grip on pros and cons of each system. Given all my research I am close to getting the 720 with power because of the price difference (the polar power option is about a third the price of powertap pro) but I must say that I haven't read too many comments from people who own the Polar power device and LOVE it. Most comments are complaints about installation or limitations on capturing low power readings etc.

Anyone out there LOVE their Polar power meter?

thx

Love, maybe not, but I do like it enough to not seriously considering going to another device....yet. I don't think any of the other devices are so much better (if at all) that it's worth re-investing in a new system. I do think there will be some new devices out in the next year or two that will cause me to upgrade though.

The polar definitely has more features than any other power meter out there and gives pretty accurate results on the road (though I think a bit optimistic). On the minus side, I doesn't work at all on most trainers and there's always that nagging in the back of your head that the power reading is off.

I've got two meters on two bikes (second sensor was only $150 used - one of the great features of it) and they correlate very well.

Good luck.

-Andy B.
 

larrynipon

New Member
Sep 17, 2003
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The Polar is fine if you are looking for RELATIVE performance tracking to determine your progress. It definitely gives bad data on a trainer, but ANY bike installed unit will not respond well on a trainer. Powertap doesn't correlate with Computrainer readings any better than Polar does. On the road, I find the Polar and Powertap units to be fairly consistent. The Polar software is actually quite good. Installation of the Polar unit can be a bit tricky if you have a bike with unusual geometry.

Originally posted by bob_chew
I am struggling between Powertap and Polar 720 with Power. I have read all the tests and I think I have a grip on pros and cons of each system. Given all my research I am close to getting the 720 with power because of the price difference (the polar power option is about a third the price of powertap pro) but I must say that I haven't read too many comments from people who own the Polar power device and LOVE it. Most comments are complaints about installation or limitations on capturing low power readings etc.

Anyone out there LOVE their Polar power meter?

thx
 

kneighbour

New Member
Apr 30, 2003
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I have used this on two bikes now - and I am fairly pleased with it. Mind you, here in Australia it is VERY expensive, so it is vary hard to say I have bought a dud.

My biggest problems with the Power Sensor are -

- the thing has to be perfectly level. It can often get bumped a bit, and then the cadence sensor won't be picked up, etc.
- the cadence magnet falls off all the time. I think have had 4 or 5 magnets now.
- I am always worried about the wire to the chain speed sensor - it looks like it is going to get caught in the chain/sprockets. It hasn't yet, but I feel it is only a matter of time.
- the magnet drags the chain down when you are stopped. This looks weird, but has not caused a problem yet. You have to put a plastic cover on top of the sensor as this chain dragging wrecks the sensor unit.

My problems with the S720i were legion -

- the LCD screen gets a rainbow pattern in low light situations - especially early mornings. It can be that bad you simply cannot read the screen. I returned two units for this problem - eventually giving up and swapping the S720i for a S710i. This seems better, although not perfect.

- the bike functions are poorly thought out - you cannot select combinations of functions, etc. All bike functions are really only on the top line - very hard to read when actually on the bike.

- the thing stops recording after about 15 or 20 minutes of no HRM. It says 30 minutes, but it is shorter than that. Under the 30 minutes, you should be able to make the thing "relearn" your chest transmitter - but there is a bug in the system that stops this ever working. After 30 minutes, the recording simply shuts down - you have no way of restarting it. You are meant to "Stop" and then restart the recording - but that never actually works either.

- there is NO ride distance function. Completely weird. There is a Trip function that records multipule rides, but as this is never reset, this cannot be used for ride distance.

- interference can be a REAL problem. This is not a real problem on the bike, but it can so muck up your recordings that it can be quite difficult to remove with the error correction software. I have done a few rides with averages around the 100+ kph.

- downloading to the PC can be hit and miss. The USB connection is prone to error and in fact I could never get mine to work so I had to revert to the Serial interface. Downloading can be very slow as you may have to retry 4 or 5 times before it finally all gets there.

While all this sounds pretty bad - the unit is actually fairly good overall, despite all the problems. I am quite happy with it. The software is really good - without that, I don't think I would ever have bought one. I just treat it as a"work in progress" - I am sure that Polar will resolve all of the problems in time.
 

RPLewis

New Member
Jun 27, 2003
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I've had a S720 with power unit for the last year. In a nut-shell all of the Power metering systems out on the market at this time (possibly excepting the Scientific SRM) have some issue or another. All watches tell the time, but all will report different times unless synchronised in some manner. Each PM system has operational difficulties and draw backs. For instance the Power Tap can't be used with disc wheels and axle cones are subject to ware. Ergomo on measures power from one side and averages etc. and will be subject to bearing wear over time.

As for the 720 the head unit (aka watch) it is excellent. The Power unit is somewhat less professional. Set up is tricky (requires measuring chain weight and centre of chainstay position) and one needs to be resourceful in finding additional packaging materials to lift the sensor unit to within the required height limits from the chain stay. The other problem is with the Cadence magnet as this can slip on the crank arm and thus lose cadence and power readings. Solution is to ensure the crank arm magnet is fully secured with a harness of zip ties or use a rare earth magnet in the back of the pedal spindal (these are so strong they just don't move). The PPP Software is good and I've had no issues with the serial port IR transmitter. However, I now download into Cycling Peaks Software directly as this supports the 720 series under PM download. Don't expect this power meter to work at all consistently whilst your on a turbo trainer or egrometer.

Basically once you understand the limitations of the system you can work with it and make use of the power information. Just remember that the information is personal to yourself and that you can't really compare your power readings between taken on the 720 and those of a friend with a PT.

Power meter measurement on the bike is relatively new and these devices are all at stage one. Second generation power meter systems will improve considerably over these first generation devices.

Enjoy working out with power.

Rick.

Originally posted by bob_chew
I am struggling between Powertap and Polar 720 with Power. I have read all the tests and I think I have a grip on pros and cons of each system. Given all my research I am close to getting the 720 with power because of the price difference (the polar power option is about a third the price of powertap pro) but I must say that I haven't read too many comments from people who own the Polar power device and LOVE it. Most comments are complaints about installation or limitations on capturing low power readings etc.

Anyone out there LOVE their Polar power meter?

thx
 

acoggan

Member
Jul 4, 2003
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Originally posted by larrynipon
ANY bike installed unit will not respond well on a trainer. Powertap doesn't correlate with Computrainer readings any better than Polar does.

The PowerTap, SRM, and Ergomo work just as well on a trainer as they do out on the road (unless your trainer happens to be too near some heavy-duty electrical equipment, thus causing interference...not a problem for most people, and usually easily solved when encountered). If you don't find agreement between your PowerTap and your Computrainer, that's because the Computrainer is wrong - period.
 

jasong

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Nov 24, 2003
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What are the known issues that would prevent the Polar system from working with a trainer? If those aren't well known, what are the suspected problems? It would seem that a trainer would give much more consistent results because you're in a much more controlled environment not leading to power spikes, you're always pedaling (mitigating the low power issues some have written about), and you're just not having to respond to conditions inherent on the road.


???
 

acoggan

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Jul 4, 2003
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The Polar calculates power by multipling chain speed by chain tension (force), with the latter determined by the frequency with which the chain vibrates (think guitar string). Since the chain is subject to all sorts of bounces and bobbles, determining the underlying, constant frequency requires a bit of sophisticated data processing to separate the true signal from the noise. The system seems to work well enough out on the road, where extraneous vibrations are random, but on a trainer or rollers the sensor will frequently 'lock on' a false signal resulting from e.g., the drumming of the rollers. Somebody recently reported that they had better success using the Polar on a trainer if they always kept the wheel speed quite low, but that may not always be possible (since resistance can only be raised so high).
 

9606

New Member
Mar 8, 2004
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acoggan - my computrainer seems to consistently read 10-15 watts below my PT. (The computrainer is calibrated & the PT torque is zeroed.) Would increasing, or decreasing, the roller pressure reduce the delta? I typically get a resistance(?) measure on the computrainer of 1.5 - 2.0.
 

acoggan

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Jul 4, 2003
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Originally posted by 9606
acoggan - my computrainer seems to consistently read 10-15 watts below my PT. (The computrainer is calibrated & the PT torque is zeroed.) Would increasing, or decreasing, the roller pressure reduce the delta? I typically get a resistance(?) measure on the computrainer of 1.5 - 2.0.

Only way to find out would be to experiment. In theory, the power reported by the Computrainer should be independent of the 'press on' force (since that is taken into account in the calculation of power), but in theory there also shouldn't be a difference between your Computrainer and your PowerTap in the first place.

Note that Computrainer accuracy claims are based on a wheel speed of ~19 mph (I believe that is the value)...so if you find yourself spinning the wheel at far lower or higher speeds, adjusting the press on force to change the rolling resistance to bring you closer to this value may be helpful.
 

djg21

New Member
Jul 14, 2003
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Originally posted by acoggan
The Polar calculates power by multipling chain speed by chain tension (force), with the latter determined by the frequency with which the chain vibrates (think guitar string). Since the chain is subject to all sorts of bounces and bobbles, determining the underlying, constant frequency requires a bit of sophisticated data processing to separate the true signal from the noise. The system seems to work well enough out on the road, where extraneous vibrations are random, but on a trainer or rollers the sensor will frequently 'lock on' a false signal resulting from e.g., the drumming of the rollers. Somebody recently reported that they had better success using the Polar on a trainer if they always kept the wheel speed quite low, but that may not always be possible (since resistance can only be raised so high).

Can I presume that the affect that you mention would occur equally with an old Velodyne, even with its relatively large flywheel? While pedaling easily, or riding at moderate tempo, I get readings on the Velodyne fairly close to those of the Polar -- off by 10-30 watts or so. When doing hard efforts, my velodyne has at times reports power output approximately 200+ watts more than that simultaneously reported by the polar. I had chalked it up to calibration and/or frequency of measurement issues.

Unfortunately, my velodyne isn't presently hooked up to a PC, and I have no way of recording data directly from it, or of determining average power outputs.
 

beerco

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Nov 8, 2003
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Originally posted by djg21
Can I presume that the affect that you mention would occur equally with an old Velodyne, even with its relatively large flywheel?

How big is the roller though? Roller diameter dictates the frequency at which any trainer induced vibrations will occur for a given wheel speed. If the Velodyne's roller is big enough, the vib's might be low enough to not affect the reading.

How high a power were you seeing the bad numbers? It's also known that the Polar under reports very high power outputs (like 1000w+ range)
 

djg21

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Jul 14, 2003
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Originally posted by beerco
How big is the roller though? Roller diameter dictates the frequency at which any trainer induced vibrations will occur for a given wheel speed. If the Velodyne's roller is big enough, the vib's might be low enough to not affect the reading.

How high a power were you seeing the bad numbers? It's also known that the Polar under reports very high power outputs (like 1000w+ range)

The roller appears to be just slightly bigger than that of a traditional trainer (e.g., kurt kinetic), perhaps with a diameter of 3". It's my guess that this stops the polar PS from properly working.

The numbers were nowhere near 1000w (I wish!). When I last did short (30 sec) intervals, the velodyne would read in excess of 500w, and the Polar would read around 350-375 watts.

The slower the speed, and lesser the effort, the closer the readings on the two devices become.
 

acoggan

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Jul 4, 2003
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Originally posted by djg21
Can I presume that the affect that you mention would occur equally with an old Velodyne, even with its relatively large flywheel? While pedaling easily, or riding at moderate tempo, I get readings on the Velodyne fairly close to those of the Polar -- off by 10-30 watts or so. When doing hard efforts, my velodyne has at times reports power output approximately 200+ watts more than that simultaneously reported by the polar. I had chalked it up to calibration and/or frequency of measurement issues.

Well, my Velodyne will definitely "thrum" quite loudly if I get the wheel spinning fast enough (generally >30-35 mph), so obviously even having the heaviest flywheel on the market doesn't damp out all vibrations. Since the flywheel is so heavy, though, it is obvious that the true source must be the tire/wheel, because if the braking motor or flywheel were significantly unbalanced the thing would readily tear itself apart. (I know one owner of a amateurishly-repaired Velodyne that had problems with an unbalanced motor.)

Note as well that transient differences in power reported by the Velodyne vs. another device are always to be expected, since powermeters measure the power input to the system, and the Velodyne either calculates or controls the power output. Input will temporarily exceed output when wheel/flywheel speed is increasing, whereas the reverse will be true when the wheel/flywheel speed is decreasing. This, along with difference calculation/updating intervals, means that only quasi-steady-state comparisons are really valid.
 

beerco

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Nov 8, 2003
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Originally posted by djg21

The numbers were nowhere near 1000w (I wish!). When I last did short (30 sec) intervals, the velodyne would read in excess of 500w, and the Polar would read around 350-375 watts.

The slower the speed, and lesser the effort, the closer the readings on the two devices become.

In addition to what Andy mentioned, it's possible that under most conditions, the roller's vibrations are low enough to not fall into the chain tension window of frequencies (bandwidth).

When you do a 30s interval, you speed up the roller to a range where the vib's are in the range the polar's looking for - which would most likely be lower in frequency than the chain's f which would under report power.

Just a thought
 

hdavies

New Member
Nov 22, 2003
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Polar Power kit,

Do people use it on the chanstay with a foam build up underneath?

If fitted as per instructions it does not work, polar do not supply anything to correct this. I get very even and consistent results off mine but have the power sensor raised about 3cm from the chanstay nearer to the chain.
 

Weisse Luft

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May 28, 2004
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Count me as a happy PPS user. It took me all of 20 minutes to install and another 10 minutes of check-out to verify all was working correctly.

Since I cannot compare to other units or stationary trainer, all I have to go by is fellow cyclists and their power meters. In the same group, our power averages are within 1-2 Watts. Last night, I had a 282 W average, PT reported 283.

For time trialing, all are equal. For bragging, the ~3 second lag on the Polar can miss bursts.

One advantage of the Polar, and its a big one, is the pedaling index with right-left balance.