Paul Lew gives masterclass in carbon wheel dynamics

Everything You Always Wanted to Ask About Carbon Wheel Dynamics, by Paul Lew, Reynolds Cycling's director of technology.
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Paul Lew, director of technology and innovation at Reynolds Cycling of Utah, has delivered a three-part masterclass in understanding wheel dynamics on the company's website. It's accompanied by a tasty photo of the carbon guru "attacking" Empire Pass, a stiff climb in Deer Valley, near Park City in Utah, up the hill from Reynolds' Salt Lake City HQ.

"In the world of wheel dynamics, the qualifications for a 'good' wheel always incorporate stiffness and compliance, or more specifically, wheels that are laterally stiff and vertically compliant," starts Lew.

"In engineering terms, this means that the wheel has minimal deflection side-to-side and at the same time moderate to large deflection in the [up-and-] down direction."

In part one of his masterclass, the carbon wheel expert discusses the relationship of these dynamic variations and the contribution of the hub, spokes, and rim as influencers of wheel characteristics.

Part two of the masterclass involves spoke crossing and rider comfort, including spoke count, spoke tension, and the influence of different types of carbon fibre angles on wheel stiffness.

"There are many conflicting opinions about how crossing spokes in a bicycle wheel influences its vertical stiffness," said Lew.

"As an engineer who’s invested nearly thirty years’ in designing and hand-building wheels, I have the experience - and data - to definitively answer the question, “How much difference does a crossing pattern make when it comes to wheel comfort?”

Testing revealed that a radial spoke pattern results in a less vertically compliant wheel than a crossing spoke pattern, but only by a very negligible amount, said Lew.

"I think most people would be surprised to see how little influence a crossing pattern has on vertical compliance and rider comfort."

He concludes: "Rider comfort and vertical deflection is best controlled by tyre pressure, not the spoke lacing pattern."

Lew also discusses the variability of carbon fibre as it pertains to bicycle wheel dynamics.

"It can be difficult to understand the material science of carbon fibre," said Lew.

"Unlike metal that is produced as a standard alloy such as 6000 series or 7000 series, carbon fibre lacks a common standard. This presents challenges, but allows a tremendous amount of customization. Reynolds embraces the infinite combinations of carbon fiber lay-up and resin combinations, and assigns different formulas to each unique area of the rim – our MR5, CR6, and PR3 technologies.

"Another complexity and another way in which metal and carbon fibre differ is that carbon fibre requires a 'system' of both carbon and resin to bind it. Here’s more detail about the two elements."

There's more on Lew - and Reyolds Cycling - from this BikeBiz tour of the Utah facility from last year.

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