Figure 4.5)
Figure 4.6)
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| Figure 4.5) |
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| Figure 4.6) |
Figures 4.5) depicts the virtual pivot, while Figure 4.6) shows the centers of curvature and lines perpendicular to the wheel path for the Giant NRS.
Note that the “virtual pivot” on the NRS is well within the rear wheel radius and relatively high above the bottom bracket. This design will behave very much like a “split-pivot mono”, described above. The idea behind this suspension, as explained on the Giant web site, is to have the suspension run just at no sag, with the rider's weight exactly countering the force from the shock. The wheel path is tilted well back relative to the frame, so that the chain force will want to extend the suspension. In this way, the NRS eliminates suspension activation through pedaling. The effect of a pedal stroke on the suspension is like a momentary increase in force from the shock. Force from a bump must overcome this additional force before the shock will activate during pedaling.
The small radius of the wheel path reduces what will probably be considerable bump feedback. These bikes should accelerate very well, but will probably not handle pedaling through technical obstacles as well as lower-pivot designs.
Tight curvature generally reduces suspension performance over large bumps to some degree, however, in the NRS, this is largely mitigated due to the high and rearward virtual pivot.
In addition, the configuration of links will probably induce some locking effect of the suspension, under braking (see the “Braking.” section for a full analysis).
We have no idea of precisely how Giant arrived at their geometry, or if the ideas behind any quantitative force theory they are using are completely sound. But as far as the information that they do provide goes, there is no overt error.