Go Back  Bike Forums > Bike Forums > Folding Bikes
Reload this Page >

A couple of observations

Folding Bikes Discuss the unique features and issues of folding bikes. Also a great place to learn what folding bike will work best for your needs.

A couple of observations

Old 04-03-19, 06:52 PM
  #1  
Schwinnsta
Schwinnasaur
Thread Starter
 
Schwinnsta's Avatar
 
Join Date: Dec 2006
Location: New Orleans, LA
Posts: 887
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 148 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
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.
Schwinnsta is offline  
Old 04-04-19, 07:27 AM
  #2  
rhenning
Senior Member
 
Join Date: Apr 2006
Posts: 3,245
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 252 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
The smaller the wheel the less stability. That is from physics. They are stronger also from physics. Roger
rhenning is offline  
Old 04-04-19, 09:51 AM
  #3  
Schwinnsta
Schwinnasaur
Thread Starter
 
Schwinnsta's Avatar
 
Join Date: Dec 2006
Location: New Orleans, LA
Posts: 887
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 148 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by rhenning View Post
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.
Schwinnsta is offline  
Old 04-04-19, 01:48 PM
  #4  
rhenning
Senior Member
 
Join Date: Apr 2006
Posts: 3,245
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 252 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
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
rhenning is offline  
Old 04-04-19, 02:45 PM
  #5  
Schwinnsta
Schwinnasaur
Thread Starter
 
Schwinnsta's Avatar
 
Join Date: Dec 2006
Location: New Orleans, LA
Posts: 887
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 148 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Well could you provide a formula or something better than just take my word for it? Show me, please.
Schwinnsta is offline  
Old 04-04-19, 05:54 PM
  #6  
rhenning
Senior Member
 
Join Date: Apr 2006
Posts: 3,245
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 252 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
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
rhenning is offline  
Old 04-04-19, 07:19 PM
  #7  
Schwinnsta
Schwinnasaur
Thread Starter
 
Schwinnsta's Avatar
 
Join Date: Dec 2006
Location: New Orleans, LA
Posts: 887
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 148 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
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.
Schwinnsta is offline  
Old 04-04-19, 08:14 PM
  #8  
2manybikes
Dog is my co-pilot
 
2manybikes's Avatar
 
Join Date: Jun 2003
Posts: 17,528

Bikes: 2 many

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 987 Post(s)
Liked 10 Times in 9 Posts
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.
2manybikes is offline  
Old 04-05-19, 07:28 AM
  #9  
Roegmann
Senior Member
 
Roegmann's Avatar
 
Join Date: Oct 2014
Location: Greater San Diego area
Posts: 81

Bikes: Pacific Cycles GT, Downtube Mini 2015 version, LitePro Crius 14"

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 32 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
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.
Roegmann is offline  
Old 04-05-19, 09:38 AM
  #10  
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 41,442

Bikes: 8

Mentioned: 183 Post(s)
Tagged: 0 Thread(s)
Quoted: 6713 Post(s)
Likes: 0
Liked 132 Times in 112 Posts
Formula? geometry of trail + Pneumatic trail , which is the shape & area of the tire contact patch
fietsbob is offline  
Old 04-05-19, 10:03 AM
  #11  
Schwinnsta
Schwinnasaur
Thread Starter
 
Schwinnsta's Avatar
 
Join Date: Dec 2006
Location: New Orleans, LA
Posts: 887
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 148 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
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.
Schwinnsta is offline  
Old 04-05-19, 10:37 AM
  #12  
Tamiya
Senior Member
 
Tamiya's Avatar
 
Join Date: May 2018
Location: AU, MY, SG & ZZZzzz...
Posts: 190
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 91 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Schwinnsta View Post
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 plus odd Arrow frame geometry too
Tamiya is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.