Mike
This is part of the voodoo feel to the whole thing. You can find an
article that says knobbies damp out shimmy. You can find another that
says knobbies supply the excitation force for shimmy. You can find
another article that states that wide tires like knobbies are
typically more compliant and therefore enable low frequency
oscillations to be amplified by the system.
My first few experiments are going to be:
1. Baseline the bike. Log initial condition of all independent
variables that I might change. Attempt to measure the frequency and
amplitude of the shimmy
2. Vary front tire pressure and ride. Note changes
3. Vary rear tire pressure and ride. Note changes
4. take reference weight (like maybe two full water bottles) and put
them at various locations on the system and note any changes
A. On front rack
B. In H2O cages
C. In jersey pocket
D. On rear rack
E. maybe elsewhere
5. Change tires
6. Change front wheel
7. Change rear wheel
8. Tighten headset or similarly damp steering
9. Load rear end heavily
10. Load front end heavily
On Dec 10, 11:44 am, Michael_S <mikeybi...@rocketmail.com> wrote:
> Funny, Bill, that you say your Hillborne shimmied. The one I had (now
> sold) was the most stable bike I've ever ridden with no hands in my
> life. I could have had a 3 course dinner while riding and not even
> think about touching the bars. I had the standard Riv supplied Tange
> headset and even with Schwalbe Smart Sams ( a knobbie tire) it was
> smooth as glass. The replacement bike, a used Ram, is not as stable,
> but is more like other bikes I've had. Neither bike has any shimmy at
> all. I did own, for a while, a Cotic Roadrat , but that baby was
> shimmy city and was sold quickly. On that bike a headset change
> quieted it as did a tire switch. But I could not get rid of it.
>
> I even think the size and shape of the rider could influence it
> dynamically as much as bike geometry and even things like tire tread
> pattern.
> As others have mentioned above, shimmy is a complex set of factors,
> and due to system (bike/rider) to system variation it can affect one
> of identical bikes and not the other.
>
> ~Mike~
>
> On Dec 10, 11:18 am, William <tapebu...@gmail.com> wrote:
>
> > Allan, thanks for that suggestion.
>
> > On Dec 10, 11:10 am, Allan in Portland <allan_f...@aracnet.com> wrote:
>
> > > BTW, there's the Bicycle Quarterly Reader's Review
> > > list,http://groups.google.com/group/bqrr, that was created as a venue for
> > > precisely these types of discussions.
>
> > > Not saying you can't discuss the mag anywhere you please, just saying
> > > we'd really appreciate the discussion there. :-)
>
> > > Carry on,
> > > -Allan- Hide quoted text -
>
> > - Show quoted text -
>
>
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