on 4/5/09 7:11 AM, Mike at [email protected] wrote: > My Rambouillet has DT Silver shifters and ghost shifts now and then. > Is it frame flex or a just a slightly miss aligned shift? I don't > know. It happens. I have cranked down on the d-rings. I have > absolutely no problems with ghost shifts on my Hilsen which has BE > Silver shifters. Still, I like friction shifting and I'm going to keep > it that way.
The whole "ghost shifting" issue is an interesting one to me, and probably a bit off the initial thread topic. I thought this topic cropped up before, but it may have been an iBob thread. There are a number of variables in the equation, to be sure: - Modern 8/9/etc casettes are designed to be easy to shift. The individual sprockets are designed to transfer the chain easily up and down under load. Simply put, they _like_ to shift. Like some of you, I learned to shift on 5 speed freewheels, which generally took learning the technique of easing up during the shift (sometimes stomping hard before shifting, so you could ease up on a climb for a revolution or two), and applying smooth pressure after the shift. - There is a load of info on "early shifting" systems in _The Dancing Chain_ by Frank Berto and on the web as well. A major component of this type of system is an upper pulley with lateral float. There has to be play in the system for it to work properly. I believe that every rear derailleur made recently has this. - Any rear sprocket set that has eight speeds or higher is spread pretty "wide", if you look at it from the top down. That means that the chain must deflect more significantly with the higher gear systems. If the chainstay is shorter, the angle of deflection will be greater. - In order to shift, you must shorten or lengthen the cable. I'm not sure how the rider input could torque the bicycle frame in a manner which would cause this to happen. - Slightly loose hubs, cassettes, freehub (where it attaches to the hub), shifting of the wheel in the dropouts (such as the QR not fully engaged or slipping on thick paint), even loose cranks or bottom bracket would be more likely to cause movement of the sprockets, and could induce the chain to "find the ramp". - A bent derailleur hanger is usually more of an issue with indexed systems, but it's worth looking at this. Occasionally, you will see one with a slight twist, which will cause some oddness and places where (combined with the floating pulley) the chain just doesn't want to stay put. - The loop at the rear derailleur is also a variable to watch. It's easy to not seat either end of the housing. Gunk tends to get into that section of cable pretty readily. It tends to be the part that restricts free cable movement, which can be an issue of non-shifting in indexed systems and imprecise shifting in friction. My Hilsen had a hiccup or two. I wasn't sure if it was user innaccuracy, so I've swapped pulleys on my rear derailleur so the fixed one is on the top, dropped a link set to run a slightly shorter chain. Hasn't done it since, even in pretty nasty conditions. http://www.flickr.com/photos/gzahnd/3285966758 I also think there's a vestigial technique from the freewheel days, which seems to help a bit. But, there definitely isn't much audible feedback from a "non-trimmed" shift. Some of that may be the rock and roll over the years, but the whole dang thing is quieter to the rider. Unlike the older freewheel systems where you had to "overshift" and trim, the current drivetrains like to be "teased" into gear. I find undershifting and smidge seems to work best. - Jim "who rode his Quickbeam fixed Saturday and his MB singlespeed today, so really has no business talking about shifting systems until he stops doing house projects and gets his Hilsen rigged back up." -- Jim Edgar [email protected] Cyclofiend Bicycle Photo Galleries - http://www.cyclofiend.com Current Classics - Cross Bikes Singlespeed - Working Bikes --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en -~----------~----~----~----~------~----~------~--~---
