Another Polar CS600 question

Discussion in 'Power Training' started by eugkimj, Feb 24, 2008.

  1. eugkimj

    eugkimj New Member

    Joined:
    Jul 28, 2007
    Messages:
    26
    Likes Received:
    0
    I recently set up my CS600 on my bike, but I have a few concerns. My main question is whether the power will be accurate given my bike's setup. The issue is the power sensor. I have a Cannondale Supersix. The chainstays are fairly thick such that the chain almost touches them in the small/small gear. This forces me to push the sensor further forward. However, the Supersix has the BB30 bottom bracket, so that the crank arms sit almost flush against the side of the bracket (instead of having the bracket cups adding space between the bracket and the arms). Hence, the crank arm is very close to the chainstay. The only way to make it work was to move the sensor forward so that the cadence sensor is at the level on the arm where the arm bows outward. In addition, I had to tilt the power sensor toward the wheel to add more room for crank arm clearance.

    With this setup, the sensor is off plane - it's not parallel to the chain front to back, and it's not level with the horizon in the side to side plane. Also, it's far enough to the front that, in the large/small combo, the chain isn't even lying over the sensor.

    I haven't tested it. It's on a Fortius trainer which I've read is not great for the Polar accuracy. It definitely reads, but the numbers are inconsistent and usually low compared to the Fortius.

    Based on the bike setup, is it likely that the CS600 isn't a great option for the Supersix?
     
    Tags:


  2. doulos

    doulos New Member

    Joined:
    Apr 22, 2007
    Messages:
    20
    Likes Received:
    0
    I'm interested in the same setup. Please let me know how it works. How about borrowing a PT wheel from someone and do some test rides for comparision? Also Tom Anhalt has lots of post on Polar setup that are very helpful.


    Good luck,
    Tim
     
  3. goodboyr

    goodboyr New Member

    Joined:
    Feb 10, 2008
    Messages:
    28
    Likes Received:
    0
    I will let T.A. chime in, but my experience is that its all about the gap between the sensor and the chain. The alignment (parallel to chain motion, tilting etc) is not important. On the other hand, you have to abide by the "1 inch square" sensor size around the large dot on the sensor as to where the chain needs to be close to. In other words, if you are in the big/small combo, what is the measurement of the gap to this 1 inch square spot? If its 25mm, you're probably ok. Better still, a picture is worth a thousand words in this case, and it would help us help you.
     
  4. veloventoux

    veloventoux New Member

    Joined:
    Nov 30, 2007
    Messages:
    25
    Likes Received:
    0
    Sorry but I dont agree with what goodboyr just said about alignment not being important. From my own experience I'd say it's maybe the most important parameter along with the chain height. So try to keep your power sensor (paddle) as // as possible with the chain. Be very careful with positionning the magnet right in front the cadence mark.
    In addition to these settings , weigh and measure carefully your chain and your CS 600 should work perfectly.
     
  5. Tom Anhalt

    Tom Anhalt New Member

    Joined:
    Dec 9, 2003
    Messages:
    239
    Likes Received:
    0
    Nope...goodboyr had it covered. "Parallelism" is immaterial, as long as how you have it mounted conforms with the chain always passing over an ~1" square area on the case centered on the "middle" mark and is never any further than 25-30mm from the top of the case at that area and you can get a consistent trigger with the cadence magnet. Period. The only thing "parallelism" helps is in reducing the likelihood of the chain rubbing on the case, but it is in no way a "requirement." BTW, acquiring a stronger magnet for the cadence trigger allows for a LOT more flexibility in mounting since you can trigger it from much further away.

    If you've ever taken apart the module case and seen the sensor (I have) and understand it's theory of operation (think "bass guitar pickup") you'll quickly realize why this is so.

    Why do you think I was able to get one of mine to work just fine on an elevated chainstay mountain bike? Yep...It was sensing the chain from BELOW the module!
    ;)
     
  6. eugkimj

    eugkimj New Member

    Joined:
    Jul 28, 2007
    Messages:
    26
    Likes Received:
    0
    This is my question. Because of the height/thickness of the chainstay and its proximity to the crank arm, the sensor sits close to the wheel. In the large/small combo, the chain does not cross anywhere near the center 1" square on the power sensor. Not too sure if the readings will be of any use like this. I guess I'll find out when it gets nice out.
     
  7. veloventoux

    veloventoux New Member

    Joined:
    Nov 30, 2007
    Messages:
    25
    Likes Received:
    0
    Well looks like you've studied the question in a very scientific way:) As I said since I run a bicycle shop I've studied it in my own empiric way. After installing the Polar CS600 on a Dedacciai Nero frame bicycle with curved chainstays and having problems of data dropouts I've installed it in the very same way on a Scott Addict frame which has straight chainstays: no more problems everything works perfectly.Period.
    As I see it you're much more likely to have your chain passing over the 1" square if your chain is //, the very shape of the paddle seems to indicate that the Polar guys must have thought the same
     
  8. goodboyr

    goodboyr New Member

    Joined:
    Feb 10, 2008
    Messages:
    28
    Likes Received:
    0
    If you think of the chain line as a diagonal line between the chain rings and cassette, and depending on the gear combo, the line changes angles, there's a spot on the chainstay where the chain position changes the least as the diagonal changes. That would be at the midpoint of the distance in the line. So, if you are having problems getting the chain to pass over the 1" inch square, for all combo's (all the combo's that you use when you ride), then getting the square near the middle of the line distance maximizes your probability of success, even if the paddle is not parallel.
     
  9. Tom Anhalt

    Tom Anhalt New Member

    Joined:
    Dec 9, 2003
    Messages:
    239
    Likes Received:
    0
    That doesn't sound good. You know what? If you can take the time to post a couple of photos of how you have it set up currently, perhaps we could make a few suggestions to help out the situation.
     
  10. jeza

    jeza New Member

    Joined:
    Mar 29, 2005
    Messages:
    2
    Likes Received:
    0
    i have an i-magic which also registers 30/40 watts more than the 600.i'm sure i have it set up correctly especially having read these threads.any idea which would be more realistic?
     
  11. Tom Anhalt

    Tom Anhalt New Member

    Joined:
    Dec 9, 2003
    Messages:
    239
    Likes Received:
    0
    Ummm....neither? I-magics aren't known for their accuracy and Polars tend to get "flaky" on a trainer.
     
  12. goodboyr

    goodboyr New Member

    Joined:
    Feb 10, 2008
    Messages:
    28
    Likes Received:
    0
    Assuming chain weight and chain stay length is accurate via measurements, I would trust the Polar. I use my bike on a Cycleops Fluid 2 and the readings are reliable and repeatable and very close to the theoretical wattage expected.
     
  13. Tom Anhalt

    Tom Anhalt New Member

    Joined:
    Dec 9, 2003
    Messages:
    239
    Likes Received:
    0
    I have the exact same trainer and my experiences are exactly opposite...it's "hit or miss" depending on the power level and cadence if the Polar reports powers that are anywhere close to "reality". I guess, as they say, YMMV ;)
     
  14. vetboy

    vetboy New Member

    Joined:
    Nov 14, 2007
    Messages:
    35
    Likes Received:
    0
    My experience is with Tom's. My CS600 reads "wonky" on my KK. Some gearing/cadence combos read OK (although even with these there is some day to day variability) , while others are no where near the ballpark.

    Joe
     
  15. goodboyr

    goodboyr New Member

    Joined:
    Feb 10, 2008
    Messages:
    28
    Likes Received:
    0
    I've installed them on two Cervelo's (an R3 and a P3C) and a new Madone 5.5 and all three are working great in all gears. (I did the constant speed tests across each gear ratio. The only inconsistency is a slightly (20 watts) lower reading in the big chain ring, biggest two cassette gears combo's). For whatever reason, things work well. Go figure!
     
Loading...
Loading...