Easiest method to adjust preload on a rear multi-link suspension.

Hella JDM

Hella JDM

Well-Known Member
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I have not been able to find a real explanation that makes sense on adjusting rear preload. Most talk about how much of the piston shaft needs to be exposed or recessed into the shock body, but this video that BC has explains it a different way, and I feel that it is way easier to understand. BC was nice enough to send me the video as I emailed them about adjusting the rear on my 2014 Civic Si. It is very simple and very easy to understand now for me, so hopefully this helps, and maybe it can be made a sticky. Here is what you do:

1. Install the rear coilover setup, put the wheel back on and set desired ride height.
2. Jack up the rear and remove wheel, then remove lower shock mount bolt.
3. Compress spring 7-10mm (1/4 to 1/2 inch basically) by jacking up the rear LCA.
4. Loosen shock body ring, and screw the shock body into or out of the base until the lower shock mount hole aligns with the LCA shock mount.
5. Reinstall lower shock bolt, put wheel back on and lower the car. Congratulations, you have just set rear preload on your multi-link rear equipped Honda (or any other multi-link car for that matter)!

Video for a graphical representation:


View: https://www.youtube.com/watch?v=tWgQ-BPd6ck


Email response from BC regarding preload adjustment:

Basically what you are doing is adjusting the shock length so that the spring is still compressed about 1/4-1/2" when the shock is fully extended. Set the ride height first and then adjust the length of the shock. You may need to readjust the shock length each time you change the ride height.
 
Question, I already adjusted everything and had my alignment done. Turns out my pre-load in the rear is a no-go. Basically, the spring is wobbling and clunks when i go on driveways and speed bumps. All I have to do is adjust my strut? so there's tension on the springs at all times? So that it doesn't wobble/clunk?

If so and all i have to do is adjust my struts, do i have to get my rears aligned again? It shouldn't affect it...
 
If your ride height is set to where you desire, you shouldn't have any alignment issues. It's actually quite easy:

Jack your car up and remove the rear wheel. I use a jack stand for the rear and keep the jack handy to actually jack up the rear suspension.

With the wheel off, put the jack under the LCA and jack it up so it doesn't fall when you take the bolt out.

Loosen the lower strut bolt (before you loosen it fully, make sure you break the collar free to adjust your preload first, it's easier this way). Play with the jack height by going up and down so you can get the bolt out easily.

Now, with the bolt out, lower the Jack so the LCA hangs free.

Grab the spring and you'll probably hear and feel the jiggling and looseness.

Now Jack up the LCA until the spring is not loose or jiggling (you'll be able to spin the spring on the perch but it won't jiggle). Basically you're taking the play out by compressing just enough to not compress the spring yet, but to have it seated properly. This is zero preload.

NOW with the spring untensioned but with no play or wiggling (zero preload), Jack up the LCA so it compresses the spring 1/4 to 1/2 inch.

With the spring set, loosen or tighten the lower strut until you can slide the bolt in the mount by hand. Your preload is set.

Now just tighten it back up, lower the Jack and you'll notice that the spring will be under tension.

Put back together and enjoy!
 
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