Bike Forums (https://www.bikeforums.net/forum.php)
-   Folding Bikes (https://www.bikeforums.net/folding-bikes/)
-   -   A couple of observations (https://www.bikeforums.net/folding-bikes/1169791-couple-observations.html)

 Schwinnsta 04-03-19 06:52 PM

A couple of observations

These may or may not be true but I think they are.
Small wheel bikes have greater low speed stability.
Rear suspension is better than front suspension.

 rhenning 04-04-19 07:27 AM

The smaller the wheel the less stability. That is from physics. They are stronger also from physics. Roger

 Schwinnsta 04-04-19 09:51 AM

Originally Posted by rhenning (Post 20869102)
The smaller the wheel the less stability. That is from physics. They are stronger also from physics. Roger

My statement is my experience but I will offer this. As the wheel's, large or small, rotation slows down they become more unstable. Since small wheels rotate faster at same speed, they will be more stable. It becomes more noticeable at very slow speeds.

 rhenning 04-04-19 01:48 PM

If you ever took a science class and paid attention to the physics of centrifugal force the size makes a large difference in this case. Dream what you want but the science is against you on this one. Roger

 Schwinnsta 04-04-19 02:45 PM

Well could you provide a formula or something better than just take my word for it? Show me, please.

 rhenning 04-04-19 05:54 PM

Find a High School Physics or Science book and spend some time reading. For that matter just look up the science of centrifugal force on the net and educate yourself. It has been 20 years since I took a HS class but I have spent 35+ years teaching it. If you want to test it spin a bicycle front wheel holding the wheel by the axle ends, try to rotate the wheels axle quickly by moving your hand rocking the wheel and it will show you what happens. Roger

 Schwinnsta 04-04-19 07:19 PM

I don't think holding a wheel in your hand is a fair test. I have stated that this holds for slow speeds on the bike. In this case the small wheel spins faster.

It matters not what degree you hold if you can't explain your self or make a logical case. Your argument is take my word for it, very scientific.

 2manybikes 04-04-19 08:14 PM

My Dahon folder Handled great. It's because the weight of the (heavy) frame Is down lower giving a nice low center of gravity. I have been though this a few times with motorcycles. The most obvious difference was between a two stroke with no overhead weight, compared to the four stroke with two cams up high that I built. wrestling the four stroke back and forth was disappointing at first. But I finally learned that riding it a lot made me stronger, and eventually I could slam it around as good as the two strokes. Just as fast in the technical stuff as my friends two strokes, or a little faster.

 Roegmann 04-05-19 07:28 AM

Ah. A pub argument, albeit for geeks, but a good one nonetheless. Here's the definitive explanation/reference (I've had this drunken argument before with my friends), The Stability of Bicycles by Lowell and McKell: American Journal of Physics: Vol. 50, No. 1. Basically,
1. The angular momentum of the turning bicycle wheels makes them act like gyroscopes to help stabilize the bicycle. This gyroscopic action also helps to turn the bike.
2. The stability of the bike is also do to centrifugal force.
3. The stability is also effected by the mass and/or width of the wheel
4. The more important factor (not overriding) is the geometry, particularly the front
The equations are complex (not just a simple PV=nRT) type.

Bigger tire, more stable. Smaller tire, more responsive.

 fietsbob 04-05-19 09:38 AM

Formula? geometry of trail + Pneumatic trail , which is the shape & area of the tire contact patch

 Schwinnsta 04-05-19 10:03 AM

Yes things like trail and such come into this but if the wheels are not moving then bike or the wheel is unstable. If small wheels on a bike or off are moving at the same speed as a large wheel then there rotational speed is proportionally greater. Quite often in physics we find formulas for movement involve an mv^2 term, m for mass and v for velocity often squared. I think as the tires slow toward zero speed the greater rotational speed of the small wheels makes it more stable.

The observation came from riding my Brompton versus riding my larger tire bikes.

 Tamiya 04-05-19 10:37 AM

Originally Posted by Schwinnsta (Post 20870950)
The observation came from riding my Brompton versus riding my larger tire bikes.

Physics all you want but you should just try riding a Raleigh Chopper!

20" rear vs 16" front :D plus odd Arrow frame geometry too

 All times are GMT -6. The time now is 10:31 AM.