So it's not the bike, it's how the load was distributed.
On 08/23/2016 01:30 PM, Sky Coulter wrote:
Tony,
Don't know how helpful this might be but I was experiencing shimmy on
my 60cm saluki, I tried a number of things to fix it, including a
needlebearing headset (which helped i think). But the biggest change
was when i swapped out the cockpit from a 90mm stem to a 100mm stem.
Shifting a bit of my weight (240lbs) forward over the front wheel
reduced the hands on shimmy more than anything else. With a load in
the front basket and hands off, there is still a bit of wagging from
the handlebars, but more like the wagging of a dog getting petted,
than oone being taken outside for a walk.
Sky in New west
On Tuesday, August 23, 2016 at 9:46:05 AM UTC-7, Trenker wrote:
Last summer I was on a short bike trip thinking to myself, during
that time on the bike when you have lots of time to think, that I
have never been bothered by shimmy on any bike that I could
remember. The same morning I kept hearing a knocking sound while
pedaling or gliding at low speed, which went away when I put both
hands lightly on the handlebar. I gradually figured out it was the
fender knocking against the tire, and I realized that I had always
experienced shimmy, but never realized it or been bothered much by
it. This is on a 66 cm Toyo Atlantis with rear panniers and a
front basket. The same morning I was having the prolonged
impression of how much I liked this bike for touring.
During that trip I had enough time to experiment and ponder the
shimmy, and I realized that it only happened at low speed, and
that at higher speeds, eg. descending on asphalt or gravel, the
bike was rock solid. Which is a nice concession.
I think shimmy can be finely tuned in or out of a bike. Going to a
slightly narrower tire can improve things, as can pumping up the
front tire to the same adequate pressure as the back; it isn’t
written in stone that the front tire has to be at a lower pressure.
Even the road surface can affect or initiate shimmy: it looks flat
but there are subtle undulations caused by car tires; they are a
lot more obvious on gravel roads, before or after intersections.
If you are tweaking your setup to reduce shimmy, you can test it
at home by standing beside the bike and rapping the side of the
handlebar with the heel of your hand: you will be able to see if
the vibrations focus on the front end ( shimmy ) or condense
around the back end of the bike ( ideal, which I now have with a
small basket on front and saddlebag tied to a small home-made rear
rack.) Tomorrow morning I head out on another short trip and I’ll
have plenty of time to see how I like this setup.
I suspect that tall riders on big bikes probably always experience
a certain amount of shimmy, as well as a certain amount of frame
flex, but we are used to it and don’t know any different. I wonder
what size your Atlantis is?
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