Polar Power Output Kit

Discussion in 'Power Training' started by grayghost, Jan 25, 2004.

  1. grayghost

    grayghost New Member

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    I am thinking about purchasing the power kit for my Polar s710 monitor. Are any of you currently using this product, if so what are your feelings vs. Power Tap.

    Please let me know both positives and negatives

    Thanks
     
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  2. redstorm

    redstorm New Member

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    Hi grayghost,

    I have been thinking about the same thing. I haven't purchased one yet although I have been considering it. From the information I have right now the only thing the unit has going for it its lower price (certainly when compared to PowerTap) and perhaps easier to handle installation (I know it seems to require a lot of adjusting but to me its easier to install than having to install a PT or SRM myself??? I might be wrong tho!) I visited the Polar booth last summer at a road racing event here (Actually it was a Polar Distributors booth) and the staff told me that I should not get the power meter but he did not specify why?

    From what I have read from multiple sites, PowerTap seems to be giving the most reliable readings for power so far. But this is based only on searching this discussion board and websites that had reviews of the units.

    I am currently considering getting the PowerTap for this summer. I just feel stupid for getting an S710 with double sensors for two bikes last summer. Now I'll have to sell the S710 and get the PowerTap.

    Ah well Let me know if you get more information!

    alp!
     
  3. RPLewis

    RPLewis New Member

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    I think your decision to got either Polar or PowerTAP is dependent on your budget and how your gonna use your power meter system.

    If you TT and use disc wheels the PT is out. If you want to use your bike on the Turbo the Polar is out. With a powertap you need to consider your rim choice carefully depending on if you want a robust training rim or a race/aero rim. Also the wheel size is fixed thus a 700c wheel won't fit 650c etc.

    PT is easier to set up as its a wheel swap with a simple wiring harness to the head unit. The wheel can be moved easily between different bikes with additional wiring kits. A Polar Power kit is needed for each bike due to the fine tuning required on the Polar setup. The Polar watch has capability for recording between two different bikes.

    R.
     
  4. tomUK

    tomUK New Member

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    PT has to be the way to go.

    There is little price difference. With the exchange rate as it currently is you would be wise to order one from the states. The cost translates to approx £474.

    You are unlikely to incure any duty or VAT as the cost of goods is too low.

    Cheers,
    Ed.
     
  5. peterwright

    peterwright New Member

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    Why not look at an Ergomo ? Great quality unit and easy to install as replacement BB. Manufacturer claims +/- 2% accuracy. I am very pleased with mine.

    Peter
     
  6. redstorm

    redstorm New Member

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  7. HarryS

    HarryS New Member

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    For whatever it is worth on this controversial topic, I'll offer my recent experience . Since I already owned a Polar S720 which I use (and love) as a bike computer I decided to invest into a power option from EBAY (~$200). Because so many articles have been written about it, I was able to install it in just about one hour, albeit I have tinkered with it quite a bit subsequently. The measurements vary from cog to cog as decribed by others when the unit is on a trainer and may differ by up to 25%. However, this difference simply went away when I used the unit on the road on a known measured incline where the differences were in the 2-3% range. I also could not find the "over-reading" error reported by others when I used it against a known power resistance provided by a Kurt Kinetics trainer. Reproducibility between rides both on the road and on the trainer have been excellent.
    Does that mean that absolute power is accurate? Probably not but that is not very important to me. The features that I like and use are ones that are hard to find in any other package.
    1.) One small watch unit as the main brains without any wireless stuff other than the heart rate belt.
    2.) Great integrated software that shows and catalogues all your workouts and graphs them in a very flexible way.
    3.) Pedaling index (PI) and left right balance can be displayed while you ride. I have used this to greatly improve my pedaling technique. I honestly believe that this feature alone is worth having the Polar. I now ride with the PI on display all the time and have noticable improved my pedaling. I have also been able to correct a slight left right imbalance that I started with. I have seen posts about this function not working. It works great on my bike. You pedal with only one foot, you get 100% of the index to that foot. You shift your preceived effort and you immediately see it. As far as I know, none of the other units have PI or L-R balance.
    4.) If you own a Polar 720, the additional cost is very small indeed. As to moving it from bike to bike, I spend another $200 and got a second unit on EBAY for my other bike (so thats an additional $400 for 2 bikes).
    5.) On the trainer, my spinerval tapes use mostly 23, 15, 13 and 12 cogs in the big ring. I measured the unit a few times against the known resistance on the Kurt Kinetics. I found that the 15 and 12 were within 2%, as was the 23, while the 17,19, &21 were reading higher by up to 20% and the 13 and 12 were reading lower. I could simply adjust the values now for this error in my training. However, I love looking at the wattage simply as an indicator to maintain my effort high for a given workout. Absolute accuracy does not matter as much.
    6.) It very light by the time you factor in the components you don't need. The actual weight penalty for me was on the order of 150g extra.

    Dislikes:
    1.) Fiddle factor during installation. If you have the local bikes store lube your chain and adjust your brakes, don't get it. If you love fiddling with your bike, this unit is a must. You can kill weekend after weekend figuring out how to improve it. As a tip, the chain speed sensor is very sensitive to position.
    2.) Cadence magnet. The one that comes with it is hardly functional. I got a rare earth magnet from radio shack and used electric tape to tape it to the inside of the crank. It has been stable since.
    3.) Handlebar mount is made for standard handlebar. I have an oversised and used wireties to attach. Not the prettiest of options but it works.
    4.) The small contacts between watch and the base. Make sure to tighten the strap real good so that the unit will not move.
    5.) variability of readout on trainer. On the plus side, it does give you cadence and speed readings from the rear wheel so can be easily used on a trainer for as long as you are careful interpreting the results.


    So all in all, I would say a valuable training tool for a few hundred dollars, particularly if you already have a Polar 720.
    There is a very interesting published scientific paper evaluating this unit out there that is rather positive. I have downloaded the pdf file. You can find it on pubmed.
    "Int J Sports Med. 2003 Apr;24(3):156-61. Validity and reliability of the Polar S710 mobile cycling powermeter. Millet GP, Tronche C, Fuster N, Bentley DJ, Candau R."
     
  8. jimh2

    jimh2 New Member

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    Well I just bought a Power Tap and had the Polar power, but never used it. I sold it on EBAY and the guy that bought it (brand new) was having problems 4 months later.
    The Power Tap seems to be a no brainer. It went on easy and the software was not a problem. I also bought an extra mounting kit for another bike ($65.00) that is something you can't do with the Polar.
    The main disadvantage of the Power tap is the weight of the wheel, its about 1100 grams. I would also recommend that if you buy the Power Tap you really get into learning how to use it and train with power, otherwise the enormous amount of data that is presented will overwhelm you.
    I would but it again, it has been helpful.
     
  9. HandyAndy

    HandyAndy New Member

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    Hi
    I am thinking of getting a polar power meter due to its low cost and I use the S720 already.Where can I find this scientific paper evaluating the unit?Would it be possible for you to email it to me at all, or just point me in the right direction.

    Andrew
     
  10. beerco

    beerco New Member

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    I trained and raced with a polar power meter for two years and it worked fairly well. The biggest issue I had was that I was never confident in the numbers it would report. Sometimes the numbers gelled but sometimes they didn't (e.g. when compared to calculated power etc.). I also tested the unit up hill in every gear and did find considerable variation between all of the gears - normally this is o.k. because it averages out when you use a variety of gears. The final straw though was when I did a 20k TT last year with a time of 30:20 (just under 25mph) but a power of 295w ave. At that power, I should have been well under 30.

    I've since sold all of my polar stuff (s710 + two power kits) and got a second hand PT for less than what I sold my polar stuff for ($450 on an OP rim).

    Having used both, I'd recommend the powertap, in spite of the polar's features.

    (btw I did a 7mile TT yesterday with the powertap in a time of 16:30 - Pave was 272 speed....25.5 - that makes much more sense!)

    p.s. The only software worth owning is CyclingPeaks btw.
     
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