What improves the efficiency of a bicycle?

Discussion in 'Cycling Equipment' started by Neil, Jun 6, 2003.

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  1. Peter Cole

    Peter Cole Guest

    "Ron Hardin" <[email protected]> wrote in message news:[email protected]...
    >
    > A loss is in additional work, not additional power.

    Thanks for the primer, but I think it's reasonable to talk about forces on the rider or power the
    rider must supply to maintain a given speed. Total work doesn't make much sense, unless you're
    counting calories.
     


  2. "Peter Cole" <[email protected]> wrote in message
    news:<[email protected]>...
    > "Ron Hardin" <[email protected]> wrote in message news:[email protected]...
    > >
    > > A loss is in additional work, not additional power.
    >
    > Thanks for the primer, but I think it's reasonable to talk about forces on the rider or power the
    > rider must supply to maintain a given speed. Total work doesn't make much sense, unless you're
    > counting calories.

    I think you missed the main point in Ron's reply.

    If you calculate the drag _forces_ the aerodynamic drag increases to the square of speed, but
    rolling resistance is _constant_ it _does_ not_ "go up with speed directly".

    If you calculate _power_ loses the aerodynamic loses increase to cube of speed and RR does "go up
    with speed directly".

    If you ride with MTB-tires, rolling resistance is very significant even at higher speeds. Even with
    good quality road tires RR is 20-50% of the total drag at the speeds of recreational cyclists
    (15-35 km/h).

    Changing from MTB-tires to good quality road tires will make you ~3-5 km/h faster at the speeds of
    15-50 km/h depending on speed an riding position. Try this:
    http://w3.iac.net/~curta/bp/velocityMetric/velocity.html.

    Joakim
     
  3. Jeff Wills

    Jeff Wills Guest

    [email protected] (Chris Zacho "The Wheelman") wrote in message
    news:<[email protected]>... <snip>
    > Here is where the benefits of a recumbent would defiitely start outweighing any downfalls.
    >

    Switching to a recumbent takes dedication- muscles and riding technique require a few months of
    adaptation. Even then, I've known a couple people who have gone back to upright riding.

    That being said, I know several 60-to-70 year olds who completed the last Cycle Oregon on
    recumbents. Some were slow, some were fast- but back-to-back 90 mile days will string out any group.
    Here's a bunch of them: http://www.geocities.com/e_r_r_c/COXV.jpeg Note preponderance of gray hair
    and Aerobellys (tm). Jeff
     
  4. Peter Cole

    Peter Cole Guest

    "Joakim Majander" <[email protected]> wrote in message
    news:[email protected]...
    > "Peter Cole" <[email protected]> wrote in message
    news:<[email protected]>...
    > > "Ron Hardin" <[email protected]> wrote in message news:[email protected]...
    > > >
    > > > A loss is in additional work, not additional power.
    > >
    > > Thanks for the primer, but I think it's reasonable to talk about forces on
    the
    > > rider or power the rider must supply to maintain a given speed. Total work doesn't make much
    > > sense, unless you're counting calories.
    >
    > I think you missed the main point in Ron's reply.
    >
    > If you calculate the drag _forces_ the aerodynamic drag increases to the square of speed, but
    > rolling resistance is _constant_ it _does_ not_ "go up with speed directly".
    >
    > If you calculate _power_ loses the aerodynamic loses increase to cube of speed and RR does "go up
    > with speed directly".

    I think that's what I said, if you find what I said ambiguous, it's what I meant, hence my comments
    about power, not work or force, being the important thing to consider.

    > If you ride with MTB-tires, rolling resistance is very significant even at higher speeds. Even
    > with good quality road tires RR is 20-50% of the total drag at the speeds of recreational cyclists
    > (15-35 km/h).
    >
    > Changing from MTB-tires to good quality road tires will make you ~3-5 km/h faster at the speeds of
    > 15-50 km/h depending on speed an riding position. Try this:
    http://w3.iac.net/~curta/bp/velocityMetric/velocity.html.

    That's a pretty crude site compared to the one I listed: www.analyticcycling.com.

    According to the (your) site:

    "The "Tire" menu choice also sets somewhat arbitrary rolling resistance coefficients. Actual
    measurements for these values are hard to come by"

    This doesn't fill me with confidence. I think hard RR numbers are out there. Where did you
    get yours?
     
  5. "Peter Cole" <[email protected]> wrote in message
    news:<[email protected]>...

    > I think that's what I said, if you find what I said ambiguous, it's what I meant, hence my
    > comments about power, not work or force, being the important thing to consider.

    You are right. I somehow missread your post.

    >
    > > If you ride with MTB-tires, rolling resistance is very significant even at higher speeds. Even
    > > with good quality road tires RR is 20-50% of the total drag at the speeds of recreational
    > > cyclists (15-35 km/h).
    > >
    > > Changing from MTB-tires to good quality road tires will make you ~3-5 km/h faster at the speeds
    > > of 15-50 km/h depending on speed an riding position. Try this:
    > http://w3.iac.net/~curta/bp/velocityMetric/velocity.html.
    >
    > That's a pretty crude site compared to the one I listed: www.analyticcycling.com.
    >
    > According to the (your) site:
    >
    > "The "Tire" menu choice also sets somewhat arbitrary rolling resistance coefficients. Actual
    > measurements for these values are hard to come by"
    >
    > This doesn't fill me with confidence. I think hard RR numbers are out there. Where did you
    > get yours?

    The site I mentioned is not mine. It uses RR coefficients of 0.012 for MTB, 0.005 for clincher and
    0.004 for tubular. They are quite close to the truth, if MTB is a knobby tire, clincher a "normal"
    road racing tire and tubular close to a track tire. The differenses between different makes, models
    and pressure are quite large (http://www.terrymorse.com/bike/rolres.html road:RR coef 0.004-0.008,
    MTB: RR 0.01-0.02)

    I like the calculator, since it gives quite a good clue how fast you can go with different bikes,
    positions and tires at a specific power. I'm familiar with www.analyticcycling.com. It also has a
    power calculator, but you need to know much more in order to use it. It is quite hard to know
    frontal areas and drag coefficients unless you have been in a wind tunnel test.

    Joakim
     
  6. "Peter Cole" <[email protected]> wrote in message
    news:<[email protected]>...

    > I didn't see where the coefficients were listed on that site, so I was judging the accuracy from
    > the annotations, which seemed pretty tentative.

    I once looked trough the actual java code.

    Joakim
     
  7. Peter Cole

    Peter Cole Guest

    "Joakim Majander" <[email protected]> wrote in message
    news:[email protected]...
    > "Peter Cole" <[email protected]> wrote in message
    news:<[email protected]>...
    >
    > > I didn't see where the coefficients were listed on that site, so I was
    judging
    > > the accuracy from the annotations, which seemed pretty tentative.
    >
    > I once looked trough the actual java code.

    Oh well, shame on me for not being that thorough.
     
  8. Review Boy

    Review Boy Guest

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