Idler bikes have been around for a while; it
would seem like a fairly obvious development that suspension designers
would experiment with the location of idler mounting.
The truth is, experimenting in suspension design is only worthwhile
if you can theoretically quantify the results. If you can’t
quantify the results theoretically, then you would have to build
and test hundreds of prototypes in order to end up with a finished
product that performs as intended. This option is just not practical.
Currently, suspension designers use a well-known graphical method
to quantify the pedalling characteristics of their proposed suspension
system. Using this method, the designer can immediately see the
effect of trying different pivot locations, link lengths, bottom
bracket location etc. This enables them to easily ‘tune’
their design so that they achieve certain design goals.
This currently known graphical method has its limitations, in
that it can only be applied to suspension systems with a ‘conventional’
drivetrain, or with a chassis mounted idler.
It is not applicable to the following systems:
- Unified Rear Triangle (Trek, Klein)
- Independent Drivetrain (GT i-Drive, Mongoose, Lapierre Pendbox)
- Swingarm Mounted Idler (Corsair, Balfa, Empire)
Until now, there has not been a suitable method for accurately
quantifying the pedalling characteristics of these systems. The
idea behind i-track suspension first originated when we devised
a graphical method that could be applied to a ‘swingarm
mounted idler’ suspension system, to quantify the Anti-Squat.
This allowed us to consider many possible configurations of this
type of system, and analyse their pedalling characteristics. We
concluded that a swingarm mounted idler suspension system didn’t
offer any great advantage over existing suspension systems.
We then took the idler concept a step further. What if the idler
was mounted on a dedicated mechanism that controlled its movement
throughout suspension travel?
In order to analyse such a concept, we devised yet another graphical
method that could be applied to this proposed system.
Using this new graphical method, we were able to analyse the pedalling
characteristics of numerous different configurations, with promising