my thoughts on cleat position with eliptical chain rings

Discussion in 'Cycling Equipment' started by Randyforriding, Dec 1, 2012.

  1. Randyforriding

    Randyforriding New Member

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    First I want to clarify something. A lot of people seem to confuse the current crop of eliptical chain rings, which do work, with Shimano Bio-pace, which didn't work. They are completely different, and in fact, work on the exact opposit pricipal.
    Leonard Zinn, who is a very smart man and knows a heck of a lot about bikes, is in favor of a rearward cleat position. In fact, he told me that he re-drills his shoes so he can move the cleats even farther back. There is some basis in logic for doing this. When your cranks are at right angles to your seat post, the ball of your foot is farther away from the bottom bracket, just as it would be with longer cranks, giving you more leverage. But there is no increase in leverage at the top and bottom of the stroke. Seems to me the results would be a lot like Bio-pace.
    But put Rotor Q-rings into the mix and things change. If you set the Q-rings at the #2 position (or even #1), rather than the
    #3 position recommended by Rotor, then a rearward cleat position gives you more leverage just where you need it. That is, you have more leverage when the effective chain ring size is biggest. I wish I could draw you some diagrams, but right now I don't have a good way of doing that. Hope my idea is clear anyway.
    By the way, this year's TDF was won on eliptical chain rings (not Rotor).

    Sorry if I sound like I'm lecturing, but I've been riding since Eisenhower was president and I have a lot of time to think and just had a few thoughts I needed to get off my chest. Wouldn't be the first time I was wrong, though. The problem with smart people (not that I'm smart) is they don't think they can be wrong. But smart people are wrong quite often.
    Randy
     
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  2. alienator

    alienator Well-Known Member

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    You need to do a careful sketch or two to consider in what directions force is applied to the pedals at the top and bottom of the pedal stroke, positions that are in the dead zone. You need to consider those vectors with respect to how the leg functions. It's the magnitude of the forces applied in those areas and the physiological constraints on force application in those areas that lead to the shape and orientation of Rotor's Q-rings and Osymetric's chain rings. As for cleat positioning, until conclusive evidence is presented, cleat position will be like pretty much everything fit related: highly dependent on the individual.
     
  3. davereo

    davereo Well-Known Member

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    I was wrong for believing.
     
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  4. Randyforriding

    Randyforriding New Member

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    I'm not sure what you are saying. Are you disagreeing with something I said, and if so, what? I've been using Q-rings for about three years now and have a pretty good understanding of how they work. The idea being the gearing is tallest where your legs can give the most push and smallest at the "dead zones". Your legs can give the most push when nearly straight, but your crank arms have the most leverage when at right angles to your angle of thrust. So, taking these both into account, your leg is past 90 degrees (but much less than 180) when the gearing is tallest. This is the opposit of Bio-pace, which I have used too, which worked on the pricipal of slowing the leg down through the "dead zones" and speeding up on the down thrust. Am I not right in this?
     
  5. Eichers

    Eichers New Member

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    Hi Randyforriding, what you have said sounds interesting and very reasonable. Rearward cleat position is what I use with traditional crankrings, because I find that it provides more support and power :)

    What length crank arms are you using with the Rotor Q-rings?
    What length crank arms would you say that is equivalent to when using standard (non-eliptical) crankrings?
     
  6. alienator

    alienator Well-Known Member

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    No, you're right on that part, but I'm not convinced of your argument on cleat position and its effect at TDC and BDC.
     
  7. Randyforriding

    Randyforriding New Member

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    To clarify the cleat position thing, with a rearward cleat position when the crankarm is at the 3 O'clock position (or nine, depending on which side you are on) the ball of your foot is farther from the bottom bracket, as it would be with longer cranks. But at the 6 and 12 O'clock positions, the ball of your foot is the same distance from the bottom bracket no matter where you poition the cleat. So my theory is that, with Q-rings, you would have more leverage where the gearing is tallest. But your leg is also capable of giving more push starting about there, which is where I could be going wrong, if I'm wrong.
     
  8. Randyforriding

    Randyforriding New Member

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    I was using 195 mm crank arms (Zinn custom), but decided that they were too long (see my other post). I'm now using 175 mm, but would like to go to 177.5. If my theory is correct about the cleat position, I think you could use a shorter crank arm than you would otherwise choose.

    An observation or two about Q-rings. Most of the time the advantage of Q-rings is subtle, if there at all. Where I have noticed the most improvement is against a headwind. I think there is some gain in climbing. On the flats with no wind, they are probably about the same as round. Down hill, they are probably a disadvantage.
    Randy
     
  9. alienator

    alienator Well-Known Member

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    In a strictly mechanical sense, any "leverage" at 3 or 9 o'clock is going to be function of the angle between a horizontal line through the pedal axle axis at the crank arm and roughly between the ankle and knee. Of course, rarely can anything physiological be completely described mechanically, and in this case the leg geometry, rider position with respect to the bottom bracket, and muscle function that yield optimal performance for an individual will also be a big factor. Moreover, there have been people who have reported that they don't get on with the rearward most placement of cleats.
     
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