If you dont really ride your bike on dirt much at all you could lower it an inch or two by tradeing it in on a sf.

 

It may not change spring rate, but increasing preload does take care of softness by increasing the amount of weight it takes to start compressing the rear suspension and makes it take more force to compress the rear suspension relative to the initial setting. The spring rate has remained the same, but it has the initial force increased by the preload before any wheel travel has been initiated. Thus though the spring rate has remained the same the suspension will take more total force per inch travel at the axle based on that preload. Where it may have taken 150 lb to compress the first inch it may now take 200 lb., 200 lb for the next inch might now take 250 lb., or whatever the linkage rate might work out to be.

 

Preload changes ONLY the amount of force it takes to start compressing a fully extended shock.

The rear suspension must have little sag just under the weight of the bike, that's called the static sag. Adjusting preload only changes the static sag.
From there on the bike sags always by same amount, no matter how much or little preload you have.
If bike used to sag an additional 2" when you sit on it (compared to static sag) it will still sag the same 2" under your weight after you added more preload.

Preload changes ONLY the amount of force it takes to start compressing a fully extended shock.

So basically it just adjust the ride height of the bike.


And going back to the original thread.
To add lowering links and then add preload to compensate for the softer spring rate is really almost the same as doing nothing.
First you lower the the rear end and you jack it up again with the preload.

Example of sag measurements.
You measure the distance from the center of the rear axle to a fixed point on the bike, say to a point on the luggage rack.
With bike lifted off the ground (fully extended shock) that measurement is say 850mm.
The you lower the bike off the stand and let it stand upright on its tires while holding the bike with the lightest touch. Now the distance between the same points is say 820mm.
Your static sag is 850mm - 820mm = 30mm.

Now gear up and sit on the bike, feet up and in normal riding position.
The suspension squatted more and now the distance between the points is 750mm.
Your race sag is 850mm - 750mm = 100mm.

If you add preload you decrease the static sag, maybe it's now only 10mm.
But when you sit on the bike it still sinks down by the same amount as before (70mm) making the race sag 80mm.

If you add a 15lb bag on the rack the bike will sink down by the same amount regardless of the preload setting.

Preload really just changes the ride height. It does not make the suspension any softer or harder.

--
Mikko

 

Would it be correct to caveat this by saying "as long as it is not a progressive spring"? If you have a progressive spring, then changing the preload will affect the sag - though I cannot say how much it will affect it. Possibly not by much?

OK, I just learned something here. I though race sag was measured by the difference between the "post static sag" height minus fully loaded weight (so in your example I thought it would be 820mm - 750mm = 70mm).

Thanks for that.

 

And that's what I meant when I said I put a little more preload on the spring. I had the sag set up perfectly for me before lowering. But once I lowered it, the bike seemed to sag too much under it's own weight. So I increased the preload. Now the bike doesn't sag too much under it's own weight, and I also have proper sag for me.

 

That will happen, as the bike will both be lowered, and the wheel rate will be lessened, causing it to sit even lower still.

Thanks to those who helped prove my first point, that most still don't understand how they work, and what exactly they do.