The Active Spoke Concept
High performance bicycle wheels typically have a low wheel rim mass (or weight). This provides
responsive acceleration especially while climbing. Conversely, a heavy mass rim has more momentum
coming out of a downhill - causing the rider to maintain higher speeds for longer.
So, it could be said that:
A wheel using Active-Spoke technology combines the best of all situations. As the speed of the rider
varies, so does the movement of mass to and from the rim.
In practice, how does it work?
Consider a 1.5oz (42g) weight that slides along a wheel spoke. Attached to this weight, is a spring that
is attached to the hub. As the speed of the wheel increases, centrifugal force will cause the weight to
move outward – to the rim. If the spring’s tension is such that the weight moves out above 20mph and
returns to the hub below 20mph, a rider climbing at say 17mph, would have a wheel with low rim
weight/inertia and responsive acceleration. Conversely, during a descent of greater than 20mph, the
weight would move out – creating a heavy rim with high inertia and added momentum to maintain higher
speeds for longer. Extend this idea to six, 1.5oz weights (~255g) and an Active -Spoke wheel is born!
The effect is significant: angular momentum increases 4 fold as the radial distance of weight from the
hub increases from 3” to 12”.
High performance bicycle wheels typically have a low wheel rim mass (or weight). This provides
responsive acceleration especially while climbing. Conversely, a heavy mass rim has more momentum
coming out of a downhill - causing the rider to maintain higher speeds for longer.
So, it could be said that:
A wheel using Active-Spoke technology combines the best of all situations. As the speed of the rider
varies, so does the movement of mass to and from the rim.
In practice, how does it work?
Consider a 1.5oz (42g) weight that slides along a wheel spoke. Attached to this weight, is a spring that
is attached to the hub. As the speed of the wheel increases, centrifugal force will cause the weight to
move outward – to the rim. If the spring’s tension is such that the weight moves out above 20mph and
returns to the hub below 20mph, a rider climbing at say 17mph, would have a wheel with low rim
weight/inertia and responsive acceleration. Conversely, during a descent of greater than 20mph, the
weight would move out – creating a heavy rim with high inertia and added momentum to maintain higher
speeds for longer. Extend this idea to six, 1.5oz weights (~255g) and an Active -Spoke wheel is born!
The effect is significant: angular momentum increases 4 fold as the radial distance of weight from the
hub increases from 3” to 12”.
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| Click Here for an animated chart of a field trial run |
| Click Here for the Roll Down Study Abstract on the Download page |
| Why does Active Spoke make sense...? |
| Active-Spoke uses centrifugal force to shift mass to and from the rim based on the rotational speed of your wheel. You’re able to install it on your existing rear wheel and it’s ideal for an out and back or any rolling course with a zero net elevation. Field trial results showed a 5 second / mile advantage over an equivalent standard wheel. |
