Can't break 40mph downhill

Discussion in 'Road Cycling' started by wiredued, Jul 20, 2005.

  1. wiredued

    wiredued New Member

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    I was at a race recently and couldn't believe the speeds they were traveling at, the previous year I was told the fastest riders were hitting 68mph on radar. How is this possible I can't break 40mph downhill I'm 6' 1" 195lbs isn't weight an advantage for downhill?
     
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  2. tourdelivermore

    tourdelivermore New Member

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    At 5' 10" and 180, all time top speed of 52.5 MPH...you should have me beat.

    Where are you cycling? Do you have steep mountains?
     
  3. OCRoadie

    OCRoadie New Member

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    Find some steeper, longer hills. On my local rides, I barely ever break 44mph. When I go to the Sierras, 50mph+ comes pretty easily.
     
  4. frenchyge

    frenchyge New Member

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    You'll probably need a decent tuck to break 50mph. 68mph sounds like an urban legend to me.
     
  5. rayner

    rayner New Member

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    Whats so hard to believe about 68mph (108kph)? If you've got a bunch of fellas working well together on a straight and steep downhill it should be pretty straightforward. If you're by yourself I'd give up now though! :) .

    @wiredued: have you tried pedalling?
     
  6. frenchyge

    frenchyge New Member

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    Why? Because in a 53x11 gear, you'd have to pedal 172rpm to achieve 68mph, and that's pretty tough to do in an aerodynamic tuck. That said, there really is no "working together" since everyone is just tucked-in coasting in each other's slipstream and only going as fast as gravity and wind-resistance allow.
     
  7. wiredued

    wiredued New Member

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    Pedaling yes I have a 52X11 but it doesn't seem to matter much... I noticed the racers were not pedaling at least they weren't when they past me at the bottom of a long hill.

     
  8. wiredued

    wiredued New Member

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    I have been trying on a monster hill near by I will try the hill used in the race to see if it makes a difference soon.

     
  9. wiredued

    wiredued New Member

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    I don't wear bicycle shorts or jersey how many mph does that cost?

     
  10. frenchyge

    frenchyge New Member

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    If you mean that you're riding naked, then that should make you faster still! Unless you're *very* well endowed, that is... :eek:

    Actually, if your t-shirt and shorts are billowing out like a parachute behind you then that'll cost you a significant amount of speed. I'd guess 3-5mph difference at 40mph depending on your position on the bike. We're talking road bike, right? 'Cause 40mph on a mountain bike would be pretty good.

    Here are my suggestions:
    Pedal at the top of the hill to get up to 25mph or so, then put your cranks horizontal and push your butt way back on the seat and drop your chin down down to the handlebars. Keep your knees and elbows in tight. Putting your hands close to the middle of the bars helps, but that's not really stable or safe, so use the drops instead. Try this on a straight stretch at first until you get comfortable with it.
     
  11. Eldrack

    Eldrack New Member

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    Longest hill I have around where I live is about 500 metres long but its fairly steep, maxed out at 42mph. Hit 25 as I got up to the hill pedaled until I was about halfway down then tucked in to get those last few mph.
     
  12. tourdelivermore

    tourdelivermore New Member

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    You know it...my 52.5 MPH was on the front side of Monitor.
     
  13. OCRoadie

    OCRoadie New Member

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    Mine was coming down from Sagehen Summit. 55 mph on my tandem, and about 53 on my regular bike. I am looking forward to a couple of days in the Sierras in the end of Sept (Everest Challenge).
     
  14. Lonnie Utah

    Lonnie Utah Banned

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    How's your aero position? Head down, back flat, legs and elbows tucked in...

    L
     
  15. wiredued

    wiredued New Member

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    I think my aerobars might be preventing me from laying on the handlebars the way the premier racers do on long descents can aerobars slow you down when you are coasting downhill? Getting my back flat seems difficult with them on. However I talked to someone who I think is a more experienced rider and he can't break 40mph either and he doesn't have aerobars.

     
  16. slickdemo

    slickdemo New Member

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    68 doesn't sound right to me either. I've hit 60 coming down a mountain, a many mile long mountain where you have plenty of straightaways, i'm 6'4" and about 175 pounds, and generally go downhill faster than my companions. but 68 is a lot faster than 60 and I'm just a tad skeptical that there's not some exageration.

    please tell me you're not descending IN your aerobars, or if you are, please promise to stop, because I don't want you to die. hands on the bars, against the stem, with your chin hovering just above your knuckles is dangerous enough.
     
  17. BikingBrian

    BikingBrian New Member

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    Very true, especially for the inexperienced. I used to be a very poor descender, and being quite light didn't help either, when I first started cycling I was about 59 kilos (130 lbs), I also could rarely break 40 mph. Now, (about 8 years later), I regularly descend the local mountains averaging about 80 kph (50 mph). I maxed out with a small group a few years ago at 91 kph (56.8 mph), this was verified by everyone in the group having similar numbers on their computers. And I still only weigh 63 kilos (139 lbs). I think a large part of descending is confidence, staying relaxed, and knowing how to carve turns.
    By the way, for the "Uber Aero Tuck" how about this: turn your hands around so your fingers are facing you (as if doing a pull-up), and "hang" from the bar tops with your nose on the stem, elbows and forearms squeezing the head tube and down tube. Guaranteed Speed! BUT (disclaimer)....this is SUPER dangerous if you don't have the skills for it, DON'T attempt it. If you can find old cycling pic's, you may come across Delgado in this pose. When I saw that pic, I knew I wanted to be able to emulate him one day, so I started practicing little by little. In the end, that's what it's all about....
     
  18. chopster

    chopster New Member

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    has anyone learned anything from physics? weight has nada to do with it. everyone has heard of the example of a hammer and a feather being dropped on the moon. they hit at the same time. so why not here? air! air resistance is the key( or lack of resistance that is). if you can get a very fast start at the top of the hill( remember, gravity is expodential) and tuck like you've never tucked before, then you will be hauling. again: fast start at top and tuck.
     
  19. BikingBrian

    BikingBrian New Member

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    Everything you say is true, hoewever there is one small detail to consider:
    generally speaking, lighter people are leaner and have their body mass spread out more than heavier people, presenting more surface area to the wind than heavier people.
    Actually, this has been discussed before, in a rec.bicycles thread as well as on weightweenies.com
     
  20. andrello

    andrello New Member

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    Wrong. Weight has a lot to do with overcoming drag. Objects only accelerate at the same rate - g. So in a vacuum they hit the ground at the same time but in air the object that can apply more force against the force of drag will hit the ground first. F=mg, i.e., a bigger m gives a bigger F which means it cancels more of the force due to drag.
     
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