Interesting thought on spring weight...

[Tony.OK]

So you have made some changes to your bike................
My example:
I've taken OEM exhaust off and replaced with race system saving a couple of kgs,
Replaced fairings with lighter race fairings,no headlights,blinkers etc,
Other parts replaced also save weight over OEM parts.

My question is at what point does it start to affect the spring weight from a stock bike,or does it not matter too much as long as you can set your sags within an acceptable range.

I had my susp replaced with Ohlins and Traxxion while my bike was still a road bike but have since converted to racing and in the process have dumped a fair amount of weight from my bike.
Is it better to have the preload 'in the middle' of required settings or at the beginning of the springs compression?.......if ya get what I mean.

[HDTboy]

The counter question to this is: Because you're going faster now without all those heavy/ expensive parts, do you need to increase your spring rate?

[Tony.OK]

The counter question to this is: Because you're going faster now without all those heavy/ expensive parts, do you need to increase your spring rate?

Mmmm.................blardy good point

[Robert Taylor]

So you have made some changes to your bike................
My example:
I've taken OEM exhaust off and replaced with race system saving a couple of kgs,
Replaced fairings with lighter race fairings,no headlights,blinkers etc,
Other parts replaced also save weight over OEM parts.

My question is at what point does it start to affect the spring weight from a stock bike,or does it not matter too much as long as you can set your sags within an acceptable range.

I had my susp replaced with Ohlins and Traxxion while my bike was still a road bike but have since converted to racing and in the process have dumped a fair amount of weight from my bike.
Is it better to have the preload 'in the middle' of required settings or at the beginning of the springs compression?.......if ya get what I mean.

In the end event you need to very pedantically measure the rider sag and static sag to see what the correlation is, that will tell you whether the spring rates are ''in the window''. Lightening bikes requires lighter springs but there are many other factors that come into play, for example how early you are on the throttle and how long you keep the throttle pinned!!!!
In a GSXR1000 for example the difference between having the rear axle fully forward and fully back is 1/2 a spring rate, simply because you are altering the leverage on the shock.
As another example compare Dunlop N-Tecs to Pirelli / Metzeler. N-Tecs require a relatively weaker low speed damping curve combined with a heavier spring with relatively minimal preload. All because the stiff tyre carcass applies different loadings and ''energy'' into the suspension. Pirelli / Metzeler have a softer carcass that moves more and in turn the low speed compression shimming and internal by pass bleed needs to be a lot firmer, combined with a softer spring with lots of preload.
Sag correlation is an indicator rather than a hard and fast ruling. If anyone tells you ''these are the magic numbers'' well maybe so for him and his tyre and his linkage and his riding style, get the picture?
As a general rule though if the rear spring is preloaded much more than 18mm the spring is either too soft or you are trying to compensate for weak hydraulic squat control. Cheap shocks though have very little or no low speed compression damping ( e.g Hyosung 650 ) and in a futile attempt to afford some form of dynamic ride height control will use either a very heavily preloaded soft spring ( sometimes 40-50mm! ) or a spring that may as well be a solid block of steel
Different cicuits and different temperatures require different spring rates. When we go to meetings with top riders such as Bugden, Stroud etc sure we measure but dont get totally preoccupied with the numbers. We will test alternative spring rates, the rider, the tyres and the stopwatch will tell us what works best at that track on that day.
The variables are endless.

[Robert Taylor]

Add to my preceding post the following oversimplified statement;

Springs are about position, damping is about controlling the rate of change of position.

[Sensei]

Some good stuff in there Rob