Wavey front end on a K6

[TSM]

Originally Posted by Baph

This begs the question; if by adjusting preload you are adjusting fork height, but not affecting spring compression, how is this possible?

The only way I could see, is that with no preload applied, there is a spacer that rests at "0" height (for sake of argument). When preload is applied, this spacers height is changed.

In theory, that wouldn't change spring compression, but in reality, it probably would. Very slightly mind.

The only time your "spring compression" would work, is when the forks are fully unloaded and you twiddle the "preload" because the fork is at full extention but is still under compression then under that senario it would be compressing the spring even more.

But that is not a normal situation, look at how a fork innards are then work out the forces applied when its getting compress/under standard bike load/ when you adjust the "preload", but remember the idea that a spring compresses a predefined ammount under a given loading.

Work on the normal idea that the forks are not always at full extention.

Taken from SportRider.com:

Preload: This adjuster bears down on the shock or fork spring and shortens or extends the spring accordingly. Many people think that changing preload affects spring stiffness, and while you can compensate to a certain extent for a too-soft or too-stiff spring by using preload, the right move in that situation is to change the spring itself.

If you shorten/extend the spring, for any given weight, you are in effect compressing/uncompressing. As the article states, you can affect spring stiffness, although preload isn't really what you want to be looking at if stiffness is your aim.

EDIT: The only way to not affect compression of the spring by preload adjusters, would be to physically move up/down the spring itself.

[TSM]

Originally Posted by Baph

Taken from SportRider.com:


If you shorten/extend the spring, for any given weight, you are in effect compressing/uncompressing. As the article states, you can affect spring stiffness, although preload isn't really what you want to be looking at if stiffness is your aim.

No No, its saying compensate, not affect. Its correct in that if there is no weight already on the spring (as in front forks) then you will compress the spring.

[fizzwheel]

Did you check the tyre pressures ?

Originally Posted by TSM

No No, its saying compensate, not affect.

OK, so pedantic you want to be huh?

Read the sentence. "Many people think that changing preload affects spring stiffness, and while you can compensate to a certain extent..."

Meaning that the adjustment does affect (in a small, limited way) the compression of the spring.

The effect, regardless of this conversation, is that of handling, because of a multitude of different things to do with suspension adjustment (for example, ride height, trail etc).

[the_lone_wolf]

surely it only affects the spring stiffness in that by screwing down the preload you compress the spring, and by the very definition of a spring the more you compress it the more force it exerts back.

you haven't actually changed the spring rate, which remains constant, all you've done is move the equilibrium point somewhere further down the range of possible values

i think the article on sport rider is trying to say that if you have a spring that is too soft, by setting the preload fairly hard you can compensate somewhat, as when the heavy rider sits on the bike the additional preload allows him to have the suspension somewhere near the middle of the travel (or whatever optimum point he wants). but you cannot change the spring rate without changing the spring, so the suspension will always have a tendency to top/bottom out because preload only affects the suspension when static, the spring rate and damping will define how the forks respond to bumps and dips etc

i think anyway

[TSM]

Originally Posted by Baph

OK, so pedantic you want to be huh?

Read the sentence. "Many people think that changing preload affects spring stiffness, and while you can compensate to a certain extent..."

Meaning that the adjustment does affect (in a small, limited way) the compression of the spring.

The effect, regardless of this conversation, is that of handling, because of a multitude of different things to do with suspension adjustment (for example, ride height, trail etc).

This affect is limited and due to changing the knock on adjustments, but on the pure basis from the original post where the preload makes the spring stiffer or softer, it does not. It changes where the fork is in a compression/rebound stroke and because of that the air gap may change and give damping characteristics of a stiffer or softer spring etc etc so on and so forth we can keep on going at this all day and its a discussion you’ve had with other way way way more knowledgeable people on this forum.

[TSM]

Originally Posted by the_lone_wolf

surely it only affects the spring stiffness in that by screwing down the preload you compress the spring, and by the very definition of a spring the more you compress it the more force it exerts back.

you haven't actually changed the spring rate, which remains constant, all you've done is move the equilibrium point somewhere further down the range of possible values

i think the article on sport rider is trying to say that if you have a spring that is too soft, by setting the preload fairly hard you can compensate somewhat, as when the heavy rider sits on the bike the additional preload allows him to have the suspension somewhere near the middle of the travel (or whatever optimum point he wants). but you cannot change the spring rate without changing the spring, so the suspension will always have a tendency to top/bottom out because preload only affects the suspension when static, the spring rate and damping will define how the forks respond to bumps and dips etc

i think anyway

your words are way better than mine, your background lets you understand how forks work and that preload actualy is a 'sort' of ride height adjuster.

Originally Posted by Daimo

Tried riding Courtys SV650S this weekend and was shocked. It scared the hell out of me.

Front end feals very light, very wavey and not under control. When cornering at higher speeds, the front end is trying to go everywhere but where you want his.

His front suspension is set to the softest setting

...so should tinkering with the above and changing the setting help sort this? He'll be in for such a shock when its sorted.

Sorry Daimo but am I missing something? Are you going to set up your mates suspension based on what you feel? The preload should be set up for his weight not yours.

Originally Posted by Daimo

Going round a long easy right hander on a dual carragewayt at 80, the front just wanted to go left, then right, then left, then right.

I'm totally confused by this. Does your mate experience this too? Again...this should all be input from your mate - not you.

However, even with the preload wound off completely it should not do feel like that on a steady throttle.

Are you hitting bumps, on a steady throttle, feeling crosswinds?

Originally Posted by TSM

From all discussions had the term "preload" is flawed as is CDI to a curvey. In my mind "preload" should be called "sag adjustment" or.... "preload" is not compression of the spring.

In my mind preload should be called precompression. IMO sag is a term that should never have been used in the first place. It's very misleading. It's like saying the front end sags under braking. Stomach's and breasts sag.

When forks extend or compress, the springs inside them are under either tension or compression.

Preload is an 'additional' compression force the springs experience when the forks are at a given position. When you adjust the preload, you are either increasing or decreasing that force.

When you increase the preload, you increase the 'additional' force at any given position of the forks under compression.

Originally Posted by the_lone_wolf

...damping will define how the forks respond to bumps and dips etc

SV's don't have damping.

[TSM]

Originally Posted by stuartyboy

SV's don't have damping.

Yes they do, but not adjustment as we know it to be on forks which have adjusters. There is a damping rod in the bottom of the SV fork that does the job.

Originally Posted by stuartyboy

In my mind preload should be called precompression. IMO sag is a term that should never have been used in the first place. It's very misleading. It's like saying the front end sags under braking. Stomach's and breasts sag.

When forks extend or compress, the springs inside them are under either tension or compression.

Preload is an 'additional' compression force the springs experience when the forks are at a given position. When you adjust the preload, you are either increasing or decreasing that force.

When you increase the preload, you increase the 'additional' force at any given position of the forks under compression.


SV's don't have damping.

At a given position its going to be 'additional' compression, but because the forks are free to extend etc this additional compression will only realy do anything when fully extended or fully compressed, two of which are not the best place to have the suspention for control of the bike, if inbetweeen these to extreams the adjuster will only raise or lower the forks travel.

I think everyones understanding of preload/sag adjustment/precompression is slightly diffrent.