Bicycle Suspension - Virtual Pivot Point

The VPP (or Virtual Pivot Point) is a linkage designed bike frame that is built to activate the suspension differently depending on what inputs the suspension has received. The "Virtual Pivot" system used in bikes by Santa Cruz and Intense use a specific type of Virtual Pivot design that was originally developed and patented by Outland Bicycles in the late 1990s. The patents cover a specific linkage configuration and rear wheel travel path that is designed to aid the pedalling performance of a rear suspension bike without negatively affecting the overall bump absorption capabilities of the suspension. Yeti Cycles has created a unique rail system to eliminate pedal jacking (aka "bob"). Giant's Maestro is yet another design that works well, and is considered by many to be an attempt to replicate aspects of the dw-link design. Patents have drawn definite lines among the manufacturers.
The VPP family of suspension systems fall into the four bar linkage category. They have short links instead of the longer links on a conventional four bar (chainstay and rocker).
The VPP (Virtual Pivot Point) system used by Santa Cruz and Intense, also claims to have reduced the problem of pedal bob. Soon after the VPP was introduced, the creation of the Progressive Suspension 5th Element rear shock (based on Currnut's platform damper) near the beginning of the Millennium allowed riders to adjust almost any frame, regardless of design, to be pedaled without the pedal bob that plagued earlier designs. Other companies have followed Progressive's lead (mainly Manitou with its SPV system based on the 5th Element and Fox's ProPedal which uses a shim stack rather than an air pressurized valve) and new designs in suspension design have come out. These 'intelligent' shocks always have to compromise between their resistance to bob and performance with smaller bumps. VPP designs typically use shocks that include some sort of platform damping.
However, the four bar linkage may cause pedal bobbing, lockout, and brake jack. With the rise of more complicated shocks and a larger market share for full suspension bikes, mountain bike suspension tuners have now arrived. It is now possible to have shocks tuned to each individual rider's desires.


Source: http://en.wikipedia.org/wiki/Bicycle_suspension#VPP