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  1. #1
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    What makes a bike stable?

    Hi all,

    I'm curious what parameters make a bike stable, or shall I say, more stable. I mean the kind of stability that allows you to take both hands off your handlebars and zip up your jersey, or whatever. Like we could all do on our small ancient Schwinn's (or whatever) when we were kids. Yeah, I know all the guys in the TdF can do it, but they're athletes, and I'm not even close. So what things can help a klutz like me? Longer chainstays seem to be one item. Less "aggressive" head angle (I think that means a lower angle, like 71-72 deg, right?) seems to be another. What about bottom bracket height or drop? What about 650b rims and tires rather than 700c? What about fatter tires and/or tire pressure? What else?

    Thanks in advance, Dick

  2. #2
    Mr. Dopolina Bob Dopolina's Avatar
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    Look up "trail". It's related to the head tube angle and fork rake.

    Also, speed helps. Bikes are more stable the faster you are moving.
    Last edited by Bob Dopolina; 08-05-14 at 11:00 PM.
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  3. #3
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    Endurance road bikes have a more forgiving geometry to allow ease of riding and comfort than racing road bikes which will have a geometry designed to optimize a rider's strength and speed.

    Different bikes will ride differently depending on what kind of ride a bike manufacturer seeks for them.

  4. #4
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    As mentioned trail and chainstay length are important factors but I recently noticed that moving my saddle forward made it much more stable with no hands.

    I didn't have a problem before mind you but now it's effortless and I never have to make broad corrections if that makes sense. Don't go moving your saddle just for this reason though, I was playing with saddle fit for some knee tenderness and comfort and as a byproduct noticed the increased hands-free stability.

  5. #5
    coprolite fietsbob's Avatar
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    more trail .. until there is too much ..

  6. #6
    Long Distance Cyclist Machka's Avatar
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    Quote Originally Posted by dicktill View Post
    Hi all,

    I'm curious what parameters make a bike stable ...

    Hmmm ... probably more than 4 bicycles.









    OK, back to your regularly scheduled programming.

  7. #7
    Senior Member kleng's Avatar
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    a long wheel base

  8. #8
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    Quote Originally Posted by kleng View Post
    a long wheel base
    Yes, this is the key I believe. Also, youth. I could ride my old balloon tire single speed bike with no hands almost anywhere at almost any speed. I am now 59 and I don't trust myself to take my hands off my hybrid. Like it or not, balance declines with age.

  9. #9
    Senior Member surgeonstone's Avatar
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    n+1 where n is whatever number of bikes you have starting at 1.

  10. #10
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    Training wheels help too
    You're just trying to start an argument to show how smart you are.

  11. #11
    Senior Member spdracr39's Avatar
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    Practice.

  12. #12
    Senior Member Shimagnolo's Avatar
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  13. #13
    Senior Member Jiggle's Avatar
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    The bike steers into the direction it's falling to adjust it's cg.

  14. #14
    Decrepit Member Scooper's Avatar
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    It's a serious question that deserves a scholarly answer.

    Historical Review of Thoughts on Bicycle Self-Stability

    Click the link "StableHistoryv32Arend.pdf" on the above linked web page to download the article.

    Quote Originally Posted by Article Summary
    Summary

    This paper is the historical motivation for the Science Magazine (April 15 2011) paper [1]
    “A bicycle can be self-stable without gyroscopic or caster effects”.

    The claim in that title is only interesting if people thought otherwise. Our main thesis, documented here, is that people did and do think otherwise. Most attempts to explain bicycle self-stability have appealed either to front wheel gyroscopic effects, or to caster effects, or both.

    After an introductory Chapter 1, Chapter 2 surveys 140 years of bicycle self-stability thoughts and explanations. The final three chapters discuss the three most-important references in detail. Chapter 3 concerns the gyroscope theories of Felix Klein and Arnold Sommerfeld (1910) [2]. Since they rely on numbers from Whipple (1899) [3], we also checked Whipple’s calculations. Chapter 5 describes and critiques the best known, by far, of the papers about trail, that by David E.H. Jones (1970,2006) [4].
    - Stan

  15. #15
    Senior Member Looigi's Avatar
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    Wheelbase has very little influence. Trying riding a tandem without a stoker. It may turn slower, but it's no more stable than a single bike with nearly half the wheelbase.
    Ride more. Fret less.

  16. #16
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    What makes a stable? The rider.
    Two things are infinite: the universe and human stupidity; and I'm not sure about the former."
    ― Albert Einstein

  17. #17
    Senior Member Shimagnolo's Avatar
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    Quote Originally Posted by Mvcrash View Post
    What makes a stable? The rider.
    I beg to differ: Motorcycle Is Determined To Win Race Even Without Rider - YouTube

  18. #18
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    Having a headset that isn't too tight.

  19. #19
    Decrepit Member Scooper's Avatar
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    Even with negative trail, short wheelbase and counter-rotating very small wheels to minimize gyroscopic effect of the wheels, this riderless bicycle analog is self-stable.

    Quicktime slow motion video

    (video clip from Science article referenced in my post above.)
    - Stan

  20. #20
    Quirky Grifter LesterOfPuppets's Avatar
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    Quote Originally Posted by Lazyass View Post
    Having a headset that isn't too tight.
    Then put a steering damper on it, for those rough road downhills.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Lemond Buenos Aires Triple

  21. #21
    blah blah blah milkbaby's Avatar
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    Quote Originally Posted by Lazyass View Post
    Having a headset that isn't too tight.
    ^This is important and often overlooked; you want a headset that is in good adjustment. You can balance because your bike can steer, but if the headset is too tight and the steering doesn't react quickly enough to your body's subtle inputs while riding no-handed, you'll feel that the bike is flighty and not stable.

    Also if you google around, there have been some discussions about tight cabling which inhibits free steering of the front wheel thus making riding no-hands difficult.

  22. #22
    Senior Member BlazingPedals's Avatar
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    Don't forget fork flop. That is, a very long stem would put more weight, further in front of the headset, affecting the speed the fork falls into the turns.

  23. #23
    rugged individualist wphamilton's Avatar
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    I love this question, because there are so many authoritative and utterly wrong answers floating around the interwebs. Present company excepted of course.

    There could still be a heated debate though, as controversial as the question can be. I'll just throw this out there: do counter-rotating gyroscopes really cancel each other out with respect to stability? If not, which physical property (if any) does get cancelled out? Just food for thought ... I don't think I'll be following up in the thread.

  24. #24
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    Quote Originally Posted by Jiggle View Post
    The bike steers into the direction it's falling to adjust it's cg.
    how do it know?

  25. #25
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    The right meds.

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