René, Thanks for the comments.
However, I doubt that brake design has much of an effect on shimmy. By the way, here I define “shimmy” as a mind-numbing terror at an oscillation of maybe 120 cycles per second and an imminent crash. “Shimmy” sounds like a silly dance that they did in the 1920s, but that’s what we call it. My eight or more bikes have cantis, center-pulls and side-pulls. It’s just that it’s tricky to apply the brakes without also tensioning the arms and upper body just a little. (At least until Campy comes out with that new, mind-controlled braking system, which I hear is slated for the new, fourteen-speed group.) Jobst is the only person who has shed enough light on this problem of mine that, when I actually apply his advise, it has an effect. All praise to Jobst for that post to the FAQ all those years ago. http://sheldonbrown.com/brandt/shimmy.html Essentially what he says is that, unless there is an egregious problem with the bike, for example, loaded heavily and improperly, broken frame member, wheel an inch out of true, et cetera, it’s the rider who propagates a shimmy that was initiated by a gust of wind, a bump, or such. Jobst: “...steering action twists the top tube and down tube, storing energy...” He didn’t use this analogy, but one way to think about it is as if the frame were a guitar string that has been plucked. The string vibrates, because the energy provided by the guitarist is alternately stored and released as the metal, gut or nylon string alternately pulls against the two anchor points. A string lying flaccid on the neck of the guitar, loosened at one end, will not vibrate harmonically. Without two anchor points, a guitar string has no method for storing and releasing energy -- vibrating. Rider skill and confidence are the key to solving this. When I am already going 50 mph on a strange road, and when I look ahead and see a drop (the gradient increases precipitously), I tend to grab for the brakes. That grab, in a sense, tightens the guitar string. Last month I descended a hill only to see a hairpin turn completely covered from grass to grass with fine sand. (Et cetera. Fill in your own emergency scenario.) Tense up. Apply Brakes. Shimmy. My pals, who went through the same turn much faster, I’m sure, and half an hour earlier, didn’t even remember it. After some prodding, one of them seemed to recall what I meant and then mumbled something about mountain biking. It’s the rider. Hope this helps, Bob -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
