Am i thinking this thru correctly?- Mtbr.com
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  1. #1
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    Am i thinking this thru correctly?

    I was trying to see how much more efficient a singlespeed is than a geared bike, so i started a little impromptu experiment...

    i took my Trek 4500 gearie and my Fila Taos SS and started them from the same point at the end of the driveway and counted the number of pedal revolutions it took to reach the beginning of the driveway...

    both bikes were set to 18-38 gearing, and i used the same amount of energy pedaling them....

    on the Trek gearie it took 17 revolutions to get to the start of the driveway and i was doing 9 MPH
    on the Fila SS it took 16 and i was doing 12 MPH

    the only difference between the two bikes, gearingwise is the Trek has it's stock Shimano Alivio deraileurs, and the Fila has a shortened chain and Surly Singleator in "Push Up" mode

    i rode the experiment 5 times, and every result was the same, 17 rev/9 MPH Vs. 16 rev/12 MPH

    do you really lose that much efficiency thru the deraileur, or does it have more to do with the shortened chain, the gear ratios were identical
    Brian, there's a message in my Alpha-Bits, it says "OOOOOOOO"
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  2. #2
    Nouveau Retrogrouch SuperModerator
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    But are the tires the same?
    mtbtires.com
    The trouble with common sense is it is no longer common

  3. #3
    Gaa-zee-raaaa!
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    Quote Originally Posted by shiggy
    But are the tires the same?
    Exactly.

    On a side note, you have WAY too much time on your hands.
    Now with more vitriol!

  4. #4
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    contradictory results

    Quote Originally Posted by MacTech
    I was trying to see how much more efficient a singlespeed is than a geared bike, so i started a little impromptu experiment...

    i took my Trek 4500 gearie and my Fila Taos SS and started them from the same point at the end of the driveway and counted the number of pedal revolutions it took to reach the beginning of the driveway...

    both bikes were set to 18-38 gearing, and i used the same amount of energy pedaling them....

    on the Trek gearie it took 17 revolutions to get to the start of the driveway and i was doing 9 MPH
    on the Fila SS it took 16 and i was doing 12 MPH

    the only difference between the two bikes, gearingwise is the Trek has it's stock Shimano Alivio deraileurs, and the Fila has a shortened chain and Surly Singleator in "Push Up" mode

    i rode the experiment 5 times, and every result was the same, 17 rev/9 MPH Vs. 16 rev/12 MPH

    do you really lose that much efficiency thru the deraileur, or does it have more to do with the shortened chain, the gear ratios were identical
    Your results don't make sense. If you had the same gear setup and the same tire size then the revolutions have to be the same - the bikes are set to the same gear inches. You are miscounting the revolutions or the distances are not the same. (Try counting the teeth on the Trek again)

    Energy is much too subjective to judge. (Is the driveway sloped? Is the Trek heavier?)

  5. #5
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    has to be the tires. if all the parameters are equal on both bikes, then the results will be equal. tire size is the only relevant parameter that you did not mention. that will skew your revolution and speed calculations. use the exact same set of wheels on both bikes and try the experiment again. (must be the same because of pressure, tread wear, etc).

    The read derailleuer adds to friction and affects the transfer of energy but it does not change the gear ratio. and unless you have a super long driveway, you are not getting accurate results because the test is too short. run it over the course of a mile at least. do it slowly so you can keep an accurate count of revolutions.


    Or better yet, throw away the slide rule and calculator and just ride whatever makes you smile the most.

  6. #6
    "Mr. Britannica"
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    Quote Originally Posted by shiggy
    But are the tires the same?

    or tire pressure?

  7. #7
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    Not trying to be a jerk here - but your entire experiment is flawed. Your outcome, regardless of length, etc... is going to give you no indication as to whether or not an SS is more efficient than your gearie.

    Besides, the true value of any bike should be measured in "smiles per mile"
    Now with more vitriol!

  8. #8
    the cool nerd
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    Quote Originally Posted by Godzilla
    Besides, the true value of any bike should be measured in "smiles per mile"
    Than my ss is truly valuable Maybe too valuable to risk crashing?

  9. #9
    paintbucket
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    I think this experiment needs significantly more beer.
    When the going gets weird its bedtime.

  10. #10
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    Quote Originally Posted by wooglin
    I think this experiment needs significantly more beer.
    That's all it needs. Forget the driveway, the cheap bikes and the counting. More beer, please.

    OGG
    Spinning and Grinning...

  11. #11
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    cranks?

    tires are probably the culprit but crank arm length would come into play as well

  12. #12
    Nouveau Retrogrouch SuperModerator
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    Quote Originally Posted by disco
    tires are probably the culprit but crank arm length would come into play as well
    Different tires will change the final drive ratio and the number of pedal strokes.
    Crank length will not.

    Crank length may change the perceived effort.
    mtbtires.com
    The trouble with common sense is it is no longer common

  13. #13
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    wooglin has the right idea -- go for a real ride on a trail on each bike then liberally apply beer to situation.

    Seriously, I think your study is way too subjective. The only accurate ways to measure efficiency would be to either measure wattage output w/ one of those new cycleops hubs like they used in the TDF, or to entirely remove the human factor.

    Easy: remove the human factor: If you measure the distance covered by the bike caused by pure pedal revolutions by NOT BEING ON THE BIKE, and not allowing any coasting, then you should get an accurate apples:apples comparison of the pedaling efficiency of the drivetrains on the two bikes. However that won't take into account any of the other variables, like weight, efficiency of rider position, riding style, traction/tire performance, wasted energy (friction in each bike's moving parts - BBs, hubs, headsets, etc), list could go on and on, etc.

    More complete method: you'd have to ride same course on both bikes w/ one of those hubs that monitors wattage produced and all the rider bio vitals like heart rate, etc. You'd probably need to ride each bike several times to get any sort of accurate sample and then do something like a regression analysis to control for other variables, such as weather, trail conditions, fresh vs. tired rides, etc.

    You'd have to have a lot of time on your hands to try something like that. I'd go w/ the 'smiles per mile' formula...

  14. #14
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    That is one long arse driveway

    16-17 cranks of a 55in gear in a straight line = about 3/4 of a football field.

  15. #15
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    right idea but

    Quote Originally Posted by steelbike
    16-17 cranks of a 55in gear in a straight line = about 3/4 of a football field.
    It's 78 feet not yards, still a long driveway.

  16. #16
    paintbucket
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    Quote Originally Posted by VTSEAL
    Sciency stuff.
    Here's a better thought. Straddle each bike and kick a pedal backwards with your foot. Which one smacks your shin harder?
    When the going gets weird its bedtime.

  17. #17
    tlg
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    Quote Originally Posted by MacTech
    I was trying to see how much more efficient a singlespeed is than a geared bike, so i started a little impromptu experiment...
    Your experiment isn't measuring efficiency.

    and i used the same amount of energy pedaling them....
    You measured this energy how?

    Efficiency is the difference between power in and power out.

    do you really lose that much efficiency thru the deraileur, or does it have more to do with the shortened chain, the gear ratios were identical
    Your gear ratios weren't identical since the wheels are part of the "gear".

    Here's how you do your experiment.:
    Take your Trek 4500 gearie. Split the chain and bypass the derailleur, making it a SS with the same gear ratio.

    Do your driveway test. And I guarantee you'll get the same number of revolutions.

    Good luck accurately measuring the power input/output and speed without labratory equipment.

    For what it's worth, the efficiency of a geard bike vs SS is virtually identical. The only difference is 2 pullies. If they're bearing pullies, they're 98% efficient.

  18. #18
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    Quote Originally Posted by pacman
    Your results don't make sense. If you had the same gear setup and the same tire size then the revolutions have to be the same - the bikes are set to the same gear inches. You are miscounting the revolutions or the distances are not the same. (Try counting the teeth on the Trek again)

    Energy is much too subjective to judge. (Is the driveway sloped? Is the Trek heavier?)
    what do you know.....its not like you are a physicist or anything

  19. #19
    Nouveau Retrogrouch SuperModerator
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    Quote Originally Posted by pacman
    It's 78 feet not yards, still a long driveway.
    Sorry, no. 55 gear inches x 3.1416 x 17 revolutions = 2937.4" = 81.6 yds

    Gear inches are not the same as rollout.
    mtbtires.com
    The trouble with common sense is it is no longer common

  20. #20
    cause it's fun
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    Quote Originally Posted by wooglin
    I think this experiment needs significantly more beer.
    I second that!
    mmmmm...beerrrrrrr
    bus driver wanna be

  21. #21
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    you left out the pi(e)

    My driveway barely takes more than a turn of my 46" gear to go from one end to the other. No wonder my wife wants a bigger place.

    Quote Originally Posted by pacman
    It's 78 feet not yards, still a long driveway.

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