Freewheeling speed

heavymental
heavymental Posts: 2,076
edited September 2013 in Road general
What factors determine freewheel speed? I notice my buddy flies away from me when freewheeling. We are of similar weight and stature and although I think my bike is lighter than his I can't see that it would make a huge amount of difference. I have a decent set of wheels so I wouldn't expect his to freewheel significantly faster than mine. What's his secret!?

Comments

  • adr82
    adr82 Posts: 4,002
    Tucking yourself into a more aero position will make a significant difference, at least on descents that are long and steep enough to make it worthwhile. Watch how some of the pros go downhill for example. Just be careful you don't get too ambitious... jumping straight to trying something like this
    tumblr_inline_mrxqo8Nmbw1qz4rgp.gif
    is liable to end badly :P
  • Barteos
    Barteos Posts: 657
    Different riding positions?
    Different tyres/pressure?
  • positioning yes, and the slingshot (drafting) effect - can create enormous acceleration, even from surprising distances where you'd think the slipstream was irrelevant.
  • t4tomo
    t4tomo Posts: 2,643
    Maybe your wheels aren't as good as you think. Additional friction in the hub will make your bike slower.
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  • Hm. May be a number of factors I suppose. I've recently had new bearings so maybe I'll notice a difference next time we ride together. Am I right in saying it's mainly weight, aerodynamics and friction that are the main factors? What are the physics? I mentioned we are of similar stature because I don't think our frontal area is much different.
  • goonz
    goonz Posts: 3,106
    Have you checked his bike for an engine? Try looking in the seat tube.
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  • kajjal
    kajjal Posts: 3,380
    Weight is another factor. I weight on the way to twice what my wife does (8.5st v 15.5st) and on any downhill freewheeling I accelerate alot faster. My wifes bike is a better spec than mine :(

    Try swapping bikes for a quick downhill freewheel to see if he is still faster ;)
  • diamonddog
    diamonddog Posts: 3,426
    Kajjal wrote:
    Weight is another factor. I weight on the way to twice what my wife does (8.5st v 15.5st) and on any downhill freewheeling I accelerate alot faster. My wifes bike is a better spec than mine :(
    ^^ This, down hill I have to pedal like hell to keep up with my riding partner (51kg v 85kg) even though I get really aero knees tucked in etc. but on the flat and up hill a different story. :)
  • Barteos
    Barteos Posts: 657
    t4tomo wrote:
    Maybe your wheels aren't as good as you think. Additional friction in the hub will make your bike slower.

    Yes, the bearing/seal friction is so huge that OP needs to upgrade to ceramic bearings in order for his wheels to roll "smoother" (by 0.1W?) :wink:
  • navrig
    navrig Posts: 1,352
    Another thing which will clearly affect your downhill freewheel speed is initial speed. Obvious isn't it but sometimes you may not appreciate that those last three turns of the pedals will give enough acceleration to give you a head start. This is especially noticeable if you are behind your mate and try to catch him on the brown of the hill, you effectively catch him but at a higher speed and then shhot past giving the impression that your freewheel acceleration is better.

    Does that make sense?
  • slowbike
    slowbike Posts: 8,498
    Navrig wrote:
    Another thing which will clearly affect your downhill freewheel speed is initial speed. Obvious isn't it but sometimes you may not appreciate that those last three turns of the pedals will give enough acceleration to give you a head start. This is especially noticeable if you are behind your mate and try to catch him on the brown of the hill, you effectively catch him but at a higher speed and then shhot past giving the impression that your freewheel acceleration is better.

    Does that make sense?
    Is it a particularly scary summit?! ;)
  • Rolling resistance (be it wheel on road or bearing) increases linearly with speed. Wind resistance (for a non-streamlined shape like a bike and rider) increases, approximately, as a square of the speed. Ergo, if you're approximately the same size and weight, it's likely he has a more aero position when he's descending.
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  • navrig
    navrig Posts: 1,352
    Slowbike wrote:
    Navrig wrote:
    Another thing which will clearly affect your downhill freewheel speed is initial speed. Obvious isn't it but sometimes you may not appreciate that those last three turns of the pedals will give enough acceleration to give you a head start. This is especially noticeable if you are behind your mate and try to catch him on the brown of the hill, you effectively catch him but at a higher speed and then shhot past giving the impression that your freewheel acceleration is better.

    Does that make sense?
    Is it a particularly scary summit?! ;)


    Brilliant, didn't notice that :lol::lol::lol::lol::lol:
  • Pross
    Pross Posts: 40,412
    diamonddog wrote:
    Kajjal wrote:
    Weight is another factor. I weight on the way to twice what my wife does (8.5st v 15.5st) and on any downhill freewheeling I accelerate alot faster. My wifes bike is a better spec than mine :(
    ^^ This, down hill I have to pedal like hell to keep up with my riding partner (51kg v 85kg) even though I get really aero knees tucked in etc. but on the flat and up hill a different story. :)

    Yeah but he made the point of saying they are similar weights.