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  1. #1
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    For best ave. time.....

    Since I'm in training for a 500 mile ride, I'm a bit of a fanatic about keeping track of my ave. speed. I always consider all the conditions when evaluating my performance and now I'm curious...What is the optimum for best ave speed? Flat road out and back with no wind? (I'd actually have not had the pleasure of no wind yet this spring) It would seem you'd gain going down hills what you lost going up but that hasn't really been my experience yet. I suppose that last 10 lbs I need to lose might remedy that? Also, it just doesn't seem I'm able to gain with the wind what I lost against it. Anyone have the facts on these issues?
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  2. #2
    Senior Member DnvrFox's Avatar
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    You are fighting the laws of physics here.

    And your perception is exactly right.

    Wind drag increases in a logarithmic fashion. Twice the speed, 4 times more drag.

    Please see this excellent article, a portion of which is excerpted here:

    http://www.sheldonbrown.com/brandt/wind.html


    Wind drag is a nonlinear function of the relative wind. That is, drag does not increase in proportion (linearly) to wind but rather with the square of its speed relative to the rider. Relative wind-speed is the sum of wind and rider speed, which in still air is equal to rider speed. Direct head- and tailwinds can be combined by addition with rider speed to give relative wind-speed.
    Therefore, when you descend you are relatively less efficient as a greater portion of your slowing comes from the wind resistance which has greatly increased at a higher speed.

    Likewise, a tail wind does not make up for fighting against a head wind.

    The graphs show how both headwinds and crosswinds affect performance, and that, in an out-and-back time trial, a tailwind does not makes up for time lost riding into a headwind of the same speed. The effect of crosswinds is probably the most interesting because it has been the subject of much controversial conjecture. Although analytical, these curves accurately show the effect on bicyclists.
    Last edited by DnvrFox; 06-01-06 at 08:01 AM.

  3. #3
    The Improbable Bulk Little Darwin's Avatar
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    I haven't done a scientific study, but by how I "feel" I think that occasional gently rolling hills are best for average speed. I think the extra exertion of getting up the hill is made up for by the rest dueing the descents.

    I have come to this conclusion by comparing rail trails and/or exercycles to the local roads. There may be other factors, but I have formed a hypothesis with no real way to test it.

    However, as a little evidence, I got off the exercycle last night to refill my water bottle, and when I got back on, I had to check the resistance bcase it felt like it had been lowered... I think periodic rest may help muscles last longer. Of course, if you are doing a 10K timetrial, then your muscles should be burning when you are done.
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  4. #4
    Time for a change. stapfam's Avatar
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    If I want to judge myself for average speed- top speed or any other speed - it would be over the same route in similar conditions. When I do occasionally ride on the road- we have a few set routes and all are different. One route is relatively flat with only one long drag in it but lots of tight corners that have to be braked for and accellerated from. Then another couple of routes take in some severe hills and a few fast downhills- then once again if I start out wanting and easy ride- we take to the Marshes with no hills steeper than 2% and no longer than 200yards and relatively long straights.

    My average speed over these rides will vary from 12mph to 18mph- then take in the weather- cold rain or frost does slow me down and a 35mph headwind is not nice. Then realise that it is on a mountain bike and I may still have knobblies on and you can see taht I cannot even think about an average for one ride is good or bad.

    Then there is the distance involved- I take it slower on a 50 mile ride than I would for a 30miler. Then there is how fit I am.

    I can see why you have have asked the question but only one person can tell you the answer.
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  5. #5
    Huachuca Rider webist's Avatar
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    I have been satisfied with gradual increases in my average speed over a variety of rides over time. Four years ago, I got excited at average speeds over 11 mph. Today, regardless of conditions (other than the most extreme) I seldom fall below an average speed of 15 mph, unless intentionally recovering or riding with the spouse. Four years ago a distance over 10 miles also thrilled me. Today my daily ride is a monimum of 20. Gradual positive progress, to me anyway, is quite gratifying.
    Just Peddlin' Around

  6. #6
    Let's do a Century jppe's Avatar
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    I agree with dgreg...at least for my riding style. I'd favor rolling hills with no wind to maximize speed related to overall effort. I'll take hills over a head wind anyday. I assume the physics would support that the optimum for overall speed is flat......

  7. #7
    feros ferio John E's Avatar
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    Quote Originally Posted by jppe
    I ... I assume the physics would support that the optimum for overall speed is flat......
    Yup, and with dead-steady speed the whole time. Boring ...
    "Early to bed, early to rise. Work like hell, and advertise." -- George Stahlman
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  8. #8
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    For me, and it's personal, on a mainly flat course with turns and some rolls I can average 16.5 mph for a 20 mile ride. When I go 40 to 60 miles my average drops to around 15.

  9. #9
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    50mph tailwind the entire way makes my average jump a bit...

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