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Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

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Old 08-05-14, 10:19 PM   #1
dicktill
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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
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Old 08-05-14, 10:28 PM   #2
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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.
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Old 08-05-14, 10:48 PM   #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.
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Old 08-05-14, 10:49 PM   #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.
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Old 08-05-14, 10:54 PM   #5
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more trail .. until there is too much ..
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Old 08-06-14, 03:36 AM   #6
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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.

[HR][/HR]



[HR][/HR]

OK, back to your regularly scheduled programming.

Last edited by Machka; 08-06-14 at 06:32 AM.
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Old 08-06-14, 06:04 AM   #7
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a long wheel base
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Old 08-06-14, 06:28 AM   #8
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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.
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Old 08-06-14, 06:59 AM   #9
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n+1 where n is whatever number of bikes you have starting at 1.
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Old 08-06-14, 07:16 AM   #10
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Training wheels help too
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Old 08-06-14, 07:31 AM   #11
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Practice.
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Old 08-06-14, 07:33 AM   #12
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Dave Moulton's Blog - Dave Moulton's Bike Blog - The ideal handling*bicycle
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Old 08-06-14, 07:49 AM   #13
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The bike steers into the direction it's falling to adjust it's cg.
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Old 08-06-14, 08:41 AM   #14
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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].
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Old 08-06-14, 08:58 AM   #15
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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.
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Old 08-06-14, 09:18 AM   #16
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What makes a stable? The rider.
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Old 08-06-14, 09:27 AM   #17
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What makes a stable? The rider.
I beg to differ: Motorcycle Is Determined To Win Race Even Without Rider - YouTube
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Old 08-06-14, 10:00 AM   #18
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Having a headset that isn't too tight.
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Old 08-06-14, 12:33 PM   #19
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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.)
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Old 08-06-14, 01:38 PM   #20
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Having a headset that isn't too tight.
Then put a steering damper on it, for those rough road downhills.
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Old 08-06-14, 02:05 PM   #21
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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.
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Old 08-06-14, 02:18 PM   #22
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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.
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Old 08-06-14, 02:19 PM   #23
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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.
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Old 08-06-14, 03:14 PM   #24
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The bike steers into the direction it's falling to adjust it's cg.
how do it know?
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Old 08-06-14, 03:35 PM   #25
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The right meds.
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