Front steering ratio versus rear affecting speed wobbles

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recumpence   100 GW

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Front steering ratio versus rear affecting speed wobbles

Post by recumpence » Sep 27 2018 4:28pm

Hey guys,

I am sure this will sound like a newbie question, but, am I correct in assuming speed wobbles (weaving) can be reduced or eliminated by decreasing rear steering and increasing front steering? I am encountering this and I want to know if decreasing the rear steering amount will help?

Matt
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macribs   1 GW

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Re: Front steering ratio versus rear affecting speed wobbles

Post by macribs » Sep 28 2018 2:12am

Weave and wobbles was more a thing of the past and early bikes then of today. Don't know why that is. Better frames, suspension and tires probably? Or did we push harder young at heart? I remember they used to mention rake and contact point of front tire as one possible source, as well as non matching tire profiles or worn tires. Like a different type of tire between front and rear, like street and dual sport, or worn down tire at the rear that is flatten in profile then a new "rounded" tire profile on the front would make weaves and wobbles worse. Then o/c stress could cause wobble, like pot hole impact. But it could also be kind of like the whole bike whould start resonating and hit a magic hertz that put it all at vibration.

I remember there was two fixes commonly talked abut for solving this. One was to duck down and lay flat on the tank the other was to "stretch out the bike" with a gently roll on the throttle while hugging the tank. The roll on with the throttle I never tried because hugging the tank corrected the weaves and wobbles so then slowly reducing speed to lower then then speed when it occur'd would put you back in the safe spot.

What have changed since the less advanced bike we rode in 80's? Well frames are stiffer, often with engine as stress member. Swing arms are more often then not mono shocked and a lot stiffer in structural design. Other then that suspension has improved. Maybe improvements to geometry I don't know.

Maybe you need to talk with someone with in depth know how of frame geometry and suspension setup?

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Re: Front steering ratio versus rear affecting speed wobbles

Post by recumpence » Sep 28 2018 6:40am

This is a 4 wheel steering stand up skateboard......
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Re: Front steering ratio versus rear affecting speed wobbles

Post by macribs » Sep 28 2018 1:02pm

Oh OK now my last post made even less sense :D

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Re: Front steering ratio versus rear affecting speed wobbles

Post by www.recumbents.com » Sep 28 2018 2:15pm

I see a lot of good info if you google "skateboard steering geometry".

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