On Bicycles, and.... what else is there?

I got a new wheel for Cara, a virtual copy (except for hub color) of the wheels for the new bike. Here's a photo: The spec: H Son Plus 23 mm wide rim, White Industries T-11 hub (purple anodized), 28 black DT butted spokes, silver brass nipples. To be added: Veloplugs with electrical tape to help keep them in place. I'm done with 19 mm rims, except the ones I already have, except for time trial or climbing wheels. 23 mm matches up better with tires 25 mm and wider. Better rolling resistance, better puncture resistance, easier flat replacement, and likely better aerodynamics. The only minus is weight: 23 mm rims are a bit heavier, perhaps 50 grams. Total mass: 787.5 grams, no Veloplugs, no skewer. The weight weenie in me cringes, but the wheel's designed to be bomb-proof. 28 spokes and if you break one, you have effectively 14, and can re-true it and still ride. And 2-cross instead of radial means the spokes are pulling against more metal on the hub flange instead of ...

One issue with wheelsize is angular momentum. Jan Heine claims that 622 mm rims (700C) are best for up to 32 mm tire width, then 650B are good up to 42 mm, then "26-inch" are best for larger size. The idea is the wider tires yield larger mass and also yield a larger rolling radius relative to narrower tires at the same rim radius. This results in more angular momentum. Turning requires changing angular momentum, so more angular momentum creates more stability: more reluctance of the bike to change direction. It's been commonly asserted that trail is what controls bike stability, not angular momentum of the wheels (the "gyroscopic effect"). Trail's important, for sure, and you can make bikes where trail is the only contributor to stability (for example, ski-bikes), but the detailed analysis by Andy Ruina at Cornell has shown that angular momentum and trail both contribute, as well as center of mass. Bikes are a complex dynamic system. Angular momentu...

In the September 2010 VeloNews Magazine , which I just got in the mail today, there's a review by Zack Vestal of six aero wheel pairs Check out the magazine for all the numbers. The topic of this blog post is the rating system. That system is to rank each of the six wheels from 1 to 6 in the following categories, then to average those rankings to get a final score: Aerodynamic drag weight front wheel stiffness rear wheel stiffness rear wheel rotational inertia front wheel rotational inertia Rotational inertia describes how hard it is to change the rotation rate of an otherwise stationary wheel. For a given unit mass, its contribution to weight is obviously proportional to the mass, while the contribution to rotational inertia is proportional to the mass multiplied by the square of the distance of that mass from the axis of rotation. So mass at the rim contributes more to rotational inertia than mass at the hub. First, note that three of these rankings depend on mas...