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Old 01-05-2009, 03:31 PM   #23
Luke's Avatar
Joined: Aug 2004
Location: Idiotville, OR
Oddometer: 4,228
Originally Posted by warewolf
Gory details, please! PM/email if you like.
I measured the geometry of the swingarm parts, and wrote some Octave (Matlab) code to analyze it. The results were close to what Bill measured here:

Here's the results:

Paint f'd the colors up. And speaking of colour, the units are mixed in kg, lbs, and mm; N are kicking around in the code too.

Look at the left graph. That's force vs. the height of the axle compared to the swingarm pivot. - is below, + is above. +150mm is about where the tire hits the fender. The greenish marks are bracketing where the sag should be with the stock link.

So the suspension feels the same -just lower- when the rider sits on it. Up to 0 mm the progression is about the same- look at the leverage lines. From 0 to 100mm, the lowering link doesn't keep up, then from 100 to 150mm totally loses. In the end, it takes 1800lbs to bottom the stock suspension, but only 1000 to bottom it with the lowering link.

So the benefit of the link is that you can lower the bike and the leverage doesn't change at the laden sag position -so the road handling doesn't get really bad when keeping the stock springs- but the bottoming resistance is terrible.
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