[Fot] bumpstear

[Bill Babcock]

The best way to understand bump steer is to play with some software  
that simulates roll/bump. Other than that, just do some google  
searches and read online stuff. Most of the books I've read don't do a  
good job--no idea why.

The most important thing to understand is that you have zero bump  
steer when the upper and lower inner suspension pivots line up with  
the inner steering pivot, the upper and lower outer suspension pivots  
line up with the outer steering pivot, and the instant centers of the  
upper, lower, and steering arms all intersect at the same point.

Instant center is an imaginary line drawn through the center of each  
link. They usually intersect about twenty feet from the car. what you  
want is for all of them to come together. If you think about it, it's  
clear why this recipe would deliver zero bump steer.

The only way to achieve that is to design the suspension that way, but  
you can get in the ballpark by moving the rack up and down--at least  
you can reduce bump steer within the limited stroke of your suspension  
system.


On Sep 29, 2008, at 5:48 PM, rob wrote:

> had  a little trouble under bracking this weekend and decided its  
> time to try and understand and messure its presant bumpstear.  This  
> weekends issue was caused buy unequal caster.
>
> I have had good results with setting camber,toe and caster  and had  
> the set ups varified on a local laser machine.Funny a level floor  
> some string and a plumbob can compete with an exspensive alignment  
> machine
>
> I would like to get a list of books for info on calculating  
> bumpstear and figureing rollcenter.         thanks   rob          Ps  
> thanks for the feed back re: phones at lime rock. Seems ATT was good  
> but most of the others were not working or spotty
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Bill Babcock
Babcock & Jenkins
Billb at bnj.com
503.936.7660
www.bnj.com

Editor
Ke Nalu e-Magazine
Paddlesurfing's Web Journal

Bill at kenalu.com
www.kenalu.com
blog: www.ponohouse.com/ponoblog

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