When you increase preload you are compressing the spring (slightly) to compensate for the weight placed on it. What is comfortable with 350Lbs 2-up will feel stiff with 220lbs solo. That's why many people adjust between solo and 2-up.

 

I totally agree with you because that is what I experience when I experiment with the pre-load on my coil over's.

 

Are ALL of the experts wrong? All of them? How about some sources? Can you find any expert that agrees with you?

Are the makers of Sonic Springs wrong when they said this:
http://sonicsprings.com/catalog/prel...ch_article.php
Read that link

A spring with a lot of weight will be under more tension. The only thing affecting how much tension and how compressed it will be is how much weight is on it. What you are both failing to realize is that after you adjust the preload the spring is still just as compressed as before. Why? Because there is still just as much weight on the spring. In post 88 all the weight of the rear of the cycle is on the shocks. That is true before AND after you adjust the preload.

You seem to be thinking that after adjusting the preload the spring is under more tension. That's not true. The ONLY thing affecting how much tension the spring is under is the amount of weight on the spring. Putting more weight on the cycle put the spring under more tension. The preload does not compress the spring the way a C clamp would if you pressed on both ends of the spring. Look at the picture in post 88. Read post 88. The preload only pushes down on one end of the spring. The amount the spring is compressed is due to the weight on the springs. This is where your misunderstanding comes from.

If you disagree with ALL of the experts then someone must be misunderstanding the issue. I wonder who that might be?
When you disagree with the experts you need to try to understand what they have to say. This is true of science and any technology.

 

It make sense what are you saying but what you are missing (I think, I'm just thinking loud and listening everyone on this thread) looking at your post #88 is that the shaft is all the time full extended so when you turn the top ring down you are increasing the tension on the spring, the shaft is preventing to raise the bike. Not sure what I'm saying is right but would explain why when you set the shocks for 2 up and you ride solo the ride is stiffer.
Not sure that what I'm trying to say make sense, english is my second language, but if the shaft is full extended and you do the preload at for example 200 pound, the shaft is keeping at this point the shock the same length, the ring is just compressing the spring down 2" and when 300 pound sit on it the spring would compress another inch and that would be your sag.

 

If you are adjusting the preload when there is no weight on the bike then yes the shaft is fully extended. But what matters is what the shock is like when you ride. When you ride a cycle with the preload high the spring is not more compressed than when the preload is set low. That is what some people do not understand.

When you set the preload on a shock when there is no weight on it, the shaft is fully extended. Then you do compress the spring and think that since there is more tension on the spring there will be more tension when you ride. That's not true.

Reread post #88 and imagine changing the preload when the bike is loaded down. It's hard to change preload when the bike is loaded but if you imagine it that way you can see the shock never fully extends nor does it fully compress. It only changes the ride height. But if you get too close to either extreme it may top out or bottom out when you ride.

This is worth repeating: When you ride a cycle with the preload high the spring is not more compressed than when the preload is set low. When you ride, the weight on the cycle is what determines how much the spring is compressed.
Once you realize that then all the quotes from the experts make sense. People think that if you increase the preload you will ride around with the spring more compressed. That is wrong.

 

Dave , I agree preload is not going to change how much the shock is compressed when you sit on or ride it , nor will it change the spring rate , the rate is what it is , also adding preload technically does not stiffen the spring , it can't that would be changing the spring rate , however because you have put the spring under tension it will take more initial force to start it compressing further , thus the initial stroke to get it compressing will feel stiffer , once it starts to compress it will compress at the rate of the spring

 

Here's the crux of your problem. You do not understand that when you ride with the preload set high the spring is not compressed further than when the preload is set low. The only thing that affects how compressed the spring is is how much weight is on it. If you understand that you will understand this issue.

Preload means compressing the spring before there is a load on it. When a shock is setting on a bench the spring is under tension. When no one is sitting on a cycle and you adjust the preload you compress the spring. When you set the preload like this you assume the spring will be more compressed when you ride. That is completely wrong and the reason for your confusion. PRELOAD DOES NOT AFFECT HOW COMPRESSED A SPRING IS WHEN YOU RIDE. Understand that and you will understand what the experts say.

As the experts say"

 

Lets say we have a 6 inch spring that takes 100 pounds to compress it each inch. If you apply 200 pounds to compress it the spring will compress 2 inches (it's now compressed down to 4 inches). Now lets preload the spring one inch. It is now 5 inches long because you applied preload. If you apply 90 pounds to the spring it will not compress. It is topped out. What happens if you apply 200 pounds? It will compress down to 4 inches. That's the same as if you did not apply any preload. Understand? The spring compresses ONLY as much as the weight you apply. The preload does not affect how compressed the spring is under load (when you are riding).
Bmusg is making this same mistake.

 

As the experts say" Quote:
All preload does is change your ride height and your sag.

Which is important because that determines how much compression and extension you have available. Too much preload and you have shortened the amount of extension available, too little preload and you reduce the amount of cmpression. Your static sag is an important step.

 

It will not compress down to 4 inches if there is an inch (100lbs) of pre-load applied. If you apply 200lbs, 100 will be required to overcome the preload and the other 100 will compress the spring 1 inch. If the spring is the same length, it is not pre-loaded. What exactly do you think the term PRE-LOAD means?

So I guess you're saying the motorcycle suspension will feel exactly the same to the solo rider when it has been sag adjusted for 2 up as it did when adjusted for solo. It's just higher. That's not my experience.

Your links are all saying that preload doesn't change the spring rate, everyone agrees. Further they're saying that pre-load is used to set sag, everyone agrees here. So, if you set sag and are still bottoming out the correct solution is to change springs not crank in more preload. Mostly correct, if your shocks have alternate springs available. If they don't, you will need to figure out some means of increasing the starting force before the springs deflect to prevent bottoming. I wonder what this could be??