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  #1  
Old 10-25-2016, 09:18 AM
motorbike57 motorbike57 is offline
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Default built a low rider, but bike is unstable. anyone know why ?

I built a 20" low rider bicycle that I had intended to give to my daughter for christmas, however, once completed, I took it out for a ride and it's pretty wobbly / unstable. Can anyone tell me why? is it just the geometry of the bike ? Even just pedaling the bike, it's sort of unstable. if you dont hold the handlebars dead straight, it's wobbly. when you try to turn, it's like "whoa"...feels very unstable. Everything on the bike is tight. maybe its just that the 20" tires and the springer front end make it that way ??? I've probably built 20 or so motorized bikes so far, including a micargi puma stretch that has a springer front end, and I've never had this problem. please let me know if you know what is going on here, before I have to completely abandon the project !

cheers
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Old 10-25-2016, 11:19 AM
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azbill azbill is offline
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Default Re: built a low rider, but bike is unstable. anyone know why ?

pics would help us help you
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  #3  
Old 10-25-2016, 11:42 AM
dgm099 dgm099 is offline
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Default Re: built a low rider, but bike is unstable. anyone know why ?

I've built a few recumbents in the past. Had that type of problem on the first one, very wobbly feeling to it. Come to find out, it was the rake and trail of the front end. A couple of changes made it a very useful bike, so maybe that's it?

Good luck.
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Old 10-25-2016, 01:36 PM
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bairdco bairdco is offline
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Default Re: built a low rider, but bike is unstable. anyone know why ?

Smaller bikes are usually "twitchy," and if the front is raked out with those bent springer forks, it's going to want to "lay over" when turning or going slower, as the rake angle naturally pushes it sideways.

Not a good setup for motors, and why you don't see many lowrider bikes out for a long cruise.
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Old 10-25-2016, 03:21 PM
motorbike57 motorbike57 is offline
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Default Re: built a low rider, but bike is unstable. anyone know why ?

Quote:
Originally Posted by dgm099 View Post
I've built a few recumbents in the past. Had that type of problem on the first one, very wobbly feeling to it. Come to find out, it was the rake and trail of the front end. A couple of changes made it a very useful bike, so maybe that's it?

Good luck.
What exactly did you change that fixed the problem ?
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Old 10-26-2016, 03:25 PM
dgm099 dgm099 is offline
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Default Re: built a low rider, but bike is unstable. anyone know why ?

I read a bunch about rake and trail. I then went to a standard bike that was stock and measured out the rake and trail of it and compared it to what I had read about so I knew that I was figuring things out correctly and I had the measurements of a bike that worked well. I ended up changing the front forks out to one that wasn't quite as curved as the ones I started with. Made all the difference in the world.

https://en.wikipedia.org/wiki/Bicycl...cycle_geometry

This is a good starting point. Good Luck
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Old 10-26-2016, 03:33 PM
dgm099 dgm099 is offline
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Default Re: built a low rider, but bike is unstable. anyone know why ?

That answer isn't really very good is it?

Once you know a bit about rake and trail, there are a number of things you can change that will change the rake and trail. The angle of the head tube, the curve of the forks, adding a spacer to move the tire forward or backward (kinda like a springer does) to change the geometry, the angle that the forks exit out of the head tube. That's just a few things you can do and you can combine them together to help save the overall look of your bike and to get the actual geometry to work for ya.
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Old 10-27-2016, 08:22 AM
motorbike57 motorbike57 is offline
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Default Re: built a low rider, but bike is unstable. anyone know why ?

Quote:
Originally Posted by dgm099 View Post
That answer isn't really very good is it?

Once you know a bit about rake and trail, there are a number of things you can change that will change the rake and trail. The angle of the head tube, the curve of the forks, adding a spacer to move the tire forward or backward (kinda like a springer does) to change the geometry, the angle that the forks exit out of the head tube. That's just a few things you can do and you can combine them together to help save the overall look of your bike and to get the actual geometry to work for ya.
Good info.. thanks. I ordered a more 'straight' springer fork and hopefully that will help a bit with stability.

cheers
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Old 10-27-2016, 09:44 AM
curtisfox curtisfox is offline
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Default Re: built a low rider, but bike is unstable. anyone know why ?

Study this one also ..................Curt

http://www.chopperhandbook.com/rake.htm
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Old 11-04-2016, 11:56 AM
dgm099 dgm099 is offline
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Default Re: built a low rider, but bike is unstable. anyone know why ?

@motorbike57,
So how did it go? Is the problem solved?
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