Theory, text, illustrations, and editing by Ken Sasaki
4-bar path analysis by Peter Ejvinsson
Spanish Version translated by Antonio Osuna
Additional translation and edition for the web y José Rubio
“Linkage” suspension simulation by Gergely Kovacs
© Kenneth M. Sasaki 2001, all rights reserved
{The authors welcome the reposting or reprinting of this page or any part of it, so long as full credit is given to the authors}
Read these sections if:
You wish to understand why the following theories regarding bicycle suspensions are complete nonsense.
Skip these sections if:
You already know that most marketing, including these theories, are B.S.
The “‘Brake Induced Shock Lockout’ (BISL).” section is not difficult.
The “‘Pivot at the Chain Line’ (PCL).” section is also not difficult, as one must simply consider the problem depicted in Figure 2.5) or accept the results in “An Intuitive Look at Forces and Torques.”.
Some of the “Ellsworth’s ‘Instant Center Tracking’ (ICT).” section gets involved, but the parts where we use the different suspensions from the “The Natural Mirror Bike.” section demonstrate some of the problems very simply.
The “‘i-Drive’ – a Perpetual Motion Machine?!?!” section is not difficult at all.
The “‘Chain line does not matter in a URT’.” section is moderately difficult.
The “Bogus Marketing.” section is flat out easy.
But beware; the “False Claims for Floating Brakes.” section is the most difficult in the work. An extremely strong physics background will be needed to tackle the last false theory in this section.
As far as we can determine, Mountain Bike Action magazine (MBA) espouses “Brake Induced Shock Lockout” (BISL)., “Special Point” Theories., and “Internal Force” Theories.
It is our purpose to educate the public on these matters and MBA reaches a fairly wide audience. We thus feel it important that MBA come to correctly understand bicycle rear suspensions. To this end, we have made numerous attempts to contact Richard Cunningham and MBA, as well as having sent them this work. We have met with no success.
If any readers are acquainted with these parties, we urge them to contact Cunningham or MBA to bring these issues to their attention.
We will now apply PA and its underlying “Some Important Concepts.” to examine some well accepted, but flawed, quantitative design theories and bogus marketing. One fundamental flaw in all of the pedaling theories is the misunderstanding or neglect of the wheel effects covered in the “Center of Mass” section. These theories treat the suspension as if the chain were directly connecting the frame members, rather then connecting through the rear cogs.