BOTM & BOTY Winner
Join Date: Aug 2007
Location: Melbourne, Australia
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Thanks for that Tim. Am not really interested in anything that raises or lowers the ride height though.
For purposes of clarification, let's apply some labels to the triangle distances we're talking about here. All distances are center-of-hole distances.
A = distance between shock pivot and swingarm pivot.
B = distance between shock pivot, and dogbone pivot
C = distance between dogbone pivot, and swingarm pivot
The stock distances are: A = 69mm, B = 66mm, C = 72mm
Assuming that we leave the dogbone length alone.
If we want to lower the ride height but leave the spring rate alone, we would decrease B and lengthen A to compensate. C is left alone.
If we want to increase the ride height, but keep the same spring rate, we would increase B, and decrease A minorly to compensate (to keep the shock moving along the same path)
If we want to decrease the rising rate, but keep the same ride height, we keep A constant, and increase C. B is increased too, by as much as is required to ensure that the shock remains at the same height. Due to the decreased spring rate though, some preload may need to be added to compensate, but the overall spring rate will be more supple.
Thinking on it more, and analysing the rate ratios, it looks to me like an ideal sort of linkage plate would be:
A = 69mm
B = 73mm
C = 79mm
That should keep the ride height about the same, without needing to add more preload (or maybe just a small amount). That will also give about an extra 15mm of swingarm travel before the action starts to rise rapidly again, with the action in the main working range being more supple.
I reckon that'd go a long, long way to fixing the rear action issues for most users, and heck, even for the race-track. Racers will just choose rear spring rates as they require, but even they would still appreciate a more supple rising rate response, rather than being kicked off bumps.