stiffness Is a funny word - Why we test it
There are multiple aspects to stiffness and to best simulate the real world, we test them in isolation and combination. We test the lateral and radial stiffness of rims to get a picture of the expected performance and ride characteristics before we build them into a wheel. Tensioned spokes behave differently depending on loading and in real life the lateral and radial loads occur in combination. This means stiffness needs to be tested in more complicated ways to understand how the wheel will react. This is not straightforward (or linear) but it is important to the overall performance of our wheels.
In a perfect world of smooth pavement, any wheel build could work. However, in the real world of poor roads, potholes, surprise rocks and curbs, the resilience of a wheel is important.
things that go bump in the night
Our impact tester is designed to simulate the extremes of riding in the real world, using a weight calibrated steel anvil to impact the wheel. Using adjustable height and weight, we can develop different impact energies to evaluate the impact resistance of the wheel at different points. We then measure at spokes, in between spokes and at the valve hole to ensure all parts of the wheel meets expectation.
One of the benefits of the paired spoke design is evident in this impact test. Since the spokes meet at the rim in pairs, the wheel stays true when the wheel is impacted. Spokes momentarily de-tension under the load of the impact but not cause the wheel to go out of true. In a conventionally laced wheel where the spokes alternate side to side where they meet the rim, the impact de-tensions only one spoke pulling from one side of the hub. This makes the wheel go momentarily out of true. In a single impact, this is less important but on a bumpy road of thousands of smaller impacts, the handling of the paired spoke design excels where other wheels feel less stable.
test but verify
As has been said by politicians in the past and holds true for product development. Trust but verify. This is at the heart of our testing program. Good design begets good wheels and good testing helps confirm it was indeed good design.