Old 07-17-10, 07:48 AM
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TandemGeek
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Originally Posted by WebsterBikeMan
deforming it so that it bulges (slightly) more on the inside of the curve and stretches (slightly) on the outside of the curve. And this deformation can happen to the entire wheel to a greater or lesser extent.
Actually, it's a bit more complex than that, but doesn't really matter outside the classroom. Without going too far down the dirt road of wheel physics, remember that your wheel is still dealing with radial loads in a corner... higher radial loads than it must deal with when you're just riding in a straight line on a level road. The more speed you carry through turns adds to the equation and when you throw in a turn at the bottom of a sharp valley with an off-camber twisting uphill follow-through you no longer have that nice linear turn that's typically modeled. Instead, you find that throughout the entire complex turn you begin a maneuver where you're continually moving the bike in and out of balance by countersteering, leaning and shifting your weight to follow an unnatural line... and that seems to suggest that the wheels are under all kinds of fairly heavy radial and lateral loads where spoke tension becomes very dynamic.

As Hermes points out from his bicycle handling seminar and training, there's also more than one way to position your body and weight over a bicycle as you corner and that too skews the equation and brings different forces into play. I've been a "weight the outside pedal and torque the handlebar" rider for most of my adult life, and it really does change how a bike or tandem corner and how they "feel" in a corner. In fact, if you want to make your stoker feel more confident in corners teach them this technique... as it eliminates the 'roller coaster' effect that often times makes them feel uncomfortable as cornering forces want to push them away from the apex of the curve and throw them off into space.

Again, my cited example was used because it is an extreme condition that really tests the stability of a tandem and it's wheels. Not even negotiating a series of tight esses on a steep descent are this dynamic since they lack the G-loading at the bottom of the valley coupled with the off-camber twist in the road surface. I only introduced it in response to my personal impressions of Rolf wheels as it pertains to this thread, since it demonstrated some type of inherent stability difference between how a Rolf wheel is designed vs. a conventionally spoked 36h wheel. Frankly, I suspect it's the somewhat narrow flange spacing (50mm) & heavy right-side dishing used on Rolfs vs. the wider flange spacing (60mm) and nearly symmetrical shape and spoke tension of our conventionally spoked wheels that is coming into play more than anything else.

Bottom Line: Forget the text books for a moment, this is simply subjective impressions from real-world riding experiences. If someone doesn't find themselves riding in these types of situations and/or are more cautious and don't push the limits of their equipment, bike handling skills and judgement all that far there's a pretty good chance they won't have similar experiences to draw on. The same is true for folks who do unsupported touring and ride with heavily laden tandems; their experiences and subjective impressions of how their tandems handle under the conditions they encounter may only resonate with other teams who have "been there and done that".

Last edited by TandemGeek; 07-17-10 at 10:12 AM. Reason: grammar & a tweak to my thesis
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