Originally Posted by cyclesailor955
Minor suspension changes can make a handling difference.
2.5 mm change?Hmmm possibly. Riding the motorcycle is the only way to make that determination.
Tom Sykes,Jonathon Rea, Valentino would probably feel a difference.
Myself,let me ride before and after before I make my Guess.
When we talk about a average (s1k) rider, 99(?)% of them does not understand the basics of suspension. And that is why they do not know how the suspension actually works and which behaviour is connected to which part (spring, damping, geometry, etc).
I agree that "Minor suspension changes can make a handling difference.", it always does. But the real question is does it make any real noticeable difference for the (99%) rider, or were there originally any need to make any changes?
Then there is also this thing that bike is a hobby. And that creates a need to make changes, just because it makes the owner more happy. So for example if you change springs one step softer, that is 5% (that is 5/100) softer (and rider sag is 2.5 mm smaller), and owner is really happy! Because now the rider sag is perfect!
It does not matter if the rider notices any change in handling (he does not) because the money he spent makes him more happy every time he rides the bike, and that is a very good reason (not rational) to change the springs.
If we think the tehnikal side of the suspension; bike weight is 440(?) lbs and spec rider 187 lbs, so rider is only 30% of the total mass (I'll skip the sprung vs unsprung mass). And if rider mass changes +-27 lbs (160...214 lbs), that is only +-4% of the total mass. That is why you do not need to change springs/ stock springs are good for wide variety of rider mass.
And if you want to keep the OEM factory stock settings, but fine tune preloads to be more suitable for a 160 lbs rider. Take out 2.5 turns (1 turn is 1 mm) of preload from front. And 1.25 mm preload away from rear shock (rear linkage is about 2:1, that is why 1.25 mm at rear shock is about 2.5 mm at rear axle).