Hugh: I've had shimmies with my 58cm Atlantis. Oddly enough, and contrary to accepted wisdom, mine was induced by a moderate rear load. I used to use a Rivendell Hobo bag as a saddle bag. On a gradual downhill near where I live, with a modest amount of weight (a few pounds) in the saddlebag, coasting and sitting upright the bike would shimmy predictably at about 12 mph. Switching the bag to the handlebars (it's designed to mount either way eliminated the shimmy. This is with the stock Ultegra headset. To shimmy, I had to sit bolt upright without touching the bars. Even leaning forward would eliminate it and holding the bars anywhere would stop it.
With panniers I found that more weight on the rear than front would lead to shimmy. With more weight on the front, even shaking the bars would not start a shimmy. So I just rode the bike front loaded for a few years and only experienced one shimmy and that involved a lot of wind and long downhill. A couple of years ago I changed to the Tange headset, but it was at the same time I changed to the lower trail fork, so it's not clear what impact each of those may have had on the shimmy issue. I have not experienced any shimmy since then but then I hadn't had much of a problem as long as I was front loaded either. Of course that's entirely at odds with your experience with front loading. The Tange headset could certainly be helpful by adding some friction. Jan Heine / Bicycle Quarterly has written a lot about the shimmy issue but concluded it's pretty unpredictable, although they also recommend roller bearing headsets as one thing to try. If you have a shimmy inducing amount of weight in your basket, what happens if you take that same weight in low riding panniers on the front? Personally I think weight high up has more effect on handling than weight down low. When you think about it, the bicycle rotates about the steering axis so the closer the weight to that plane the better for handling. The opposite would be to place a lot of weight way back on the rear of the bike, a long way from the pivot point. The Tange headset is a pretty cost effective experiment. I had mine installed at my LBS & I think it was in the $100 range for parts & labor. The original one was probably OK but it was 10 years old. dougP On Saturday, February 7, 2015 at 4:22:10 PM UTC-8, hsmitham wrote: > > I'm on a roll here with another question!! > > On my Atlantis with about 5 to 6 lb load up front I have noticed the front > end shimmy with no hands (I realize that Riv say's or thinks I'm a knuckle > head for this practice) which is for only a brief time period, even with > one hand I can feel the and see the shimmy which is pretty violent above > 19-20 MPH so much so that lister Mike S. commented on it. Mike and Riv > claim that others have experienced the same and switched to the Tange > needle bearing headset resolving the issue. > > My question, has anyone out there experienced this phenomenon? And if so > did you switch to the Tange needle bearing headset and did it resolve the > shimmy or at the least reduce it. What Riv say's about more friction at the > lower race where all the force is received makes sense? I'd just like some > real world application confirmation. 'nough said. > > Thanks in advance for you experiences and feedback. > > ~Hugh > Los Angeles, CA > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To post to this group, send email to rbw-owners-bunch@googlegroups.com. Visit this group at http://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/d/optout.
