Article [13] ST1300 - Rear suspension / Resetting the pre-load adjustor [Video]

[Maciejst1300]

That "might" be a project, check out posts on this forum on the subject and relationship to SMC (Secondary Master Cylinder). Depending on the state of your bike maintenance (unknown to us) it may be as simple as cleaning/overhauling rear caliper and rear master cylinder, or cleaning/overhauling the SMC, or replacing SMC. Good articles on this forum on the subject.

Yes it is project, has been in a garage for over two years when I bought has sleaze real caliper middle cylinder and abs light is on. I've changed all calipers seals new proportion valve. I've bought vacuum pump and watched your YouTube how to bleeding and still the same.
Now I'm awaiting new abs pump.

 

[meta]

Top of the mornin to ya'll

what does this preload adjuster actually do?
what is connected to the other end of the pipe?
On the bike I bought, the guy said something about changing the bike spring thing just behind this and I think said this adjuster was disconnected now. Not sure at all about this whole area, what going on around there.
maybe someone can explain it. Ta!

 

[dduelin]

Top of the mornin to ya'll

what does this preload adjuster actually do?
what is connected to the other end of the pipe?
On the bike I bought, the guy said something about changing the bike spring thing just behind this and I think said this adjuster was disconnected now. Not sure at all about this whole area, what going on around there.
maybe someone can explain it. Ta!

If the preloader is working correctly turning it clockwise pressurizes a cylinder and forces fluid thru the hose to a collar mounted on top of the shock. Pressurizing the collar pushes it down on the shock body. The down force presses on the shock spring. The shock is fixed to the frame and to the swing arm but allowed to expand and compress. The distance the collar presses down in response to the adjuster being turned clockwise increases the length of the shock, thus raising the height of the seat from the ground. This is a static measurement.

This is the practical explanation of what the preload adjuster does. Many bikes suffer from a loss of adjuster effectiveness due to loss of fluid in the preloader mechanism or an increase in hose volume from swelling. The additional volume in the hose reduces the amount of pressure the adjuster can place on the spring....... unless the adjuster is refilled to the top to make up the additional volume. As soon as the preload cylinder applies pressure to the collar the resistance to turning the knob increases significantly. If you can turn the adjuster knob without resistance the adjuster is not applying pressure to the preload collar on the shock. The ST1300 OEM shock has 18 turns of travel which can apply up to about 10 mm of preload to the shock spring.

Lots to read in the ST1300 Suspension subform: https://www.st-owners.com/forums/forums/st1300-suspension.479/

 

[MidLife]

Top of the mornin to ya'll

what does this preload adjuster actually do?

The adjuster is to compress the spring when you carry more load on the bike, to stiffen up the suspension, to bring the back of the bike back up so your shock doesn't bottom down under the load when hitting bumps.

what is connected to the other end of the pipe?

This vid will show you more than you want to know about the shock. But if you go straight to 47:40, you'll see the remote preloader in action and how it moves the piston that compresses the spring.

On the bike I bought, the guy said something about changing the bike spring thing just behind this and I think said this adjuster was disconnected now. Not sure at all about this whole area, what going on around there.

The easy way to verify if disconnected or not is to crank the preload all the way in. If there is no resistance at all, it is "disconnected", or empty of oil.

You can also remove the bike side cover and verify if the piston, as you can see on the vid, is moving or not when cranking your adjuster.

When the preloader is connected and full, the piston should move about 9.7 mm.

Not unusual to change the spring, the OEM is on the light/soft side. But it is still better to be able to adjust the preload for carrying more weight, even with a stiffer spring.

The wire diameter of the OEM spring is about 13.15 mm (and is black). If the dia is larger than that, you have an aftermarket spring.

You may want to take a quick sag measurement with your current unadjusted preload to see how close you are from a sound ride height setting.,

 

[meta]

Excellent stuff, I have it figured out now, thanks guys