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Coilover tuning help

Waternut

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Macon, GA
I built a rear triangulated 4 link setup on my YJ about a year ago. For the most part it's been great off-road but on road is no better than leaf springs. I can live with that but what I can't understand is why the Jeep will sit at a certain height in the garage but after hitting a bump it stepping on the bumper, the shocks don't want to come all the way back up to ride height.

I've got 14" Fox coilovers with the remote reservoir. At ride height, I'm sitting 9" in the travel of the shock. My Jeep is pretty light and my springs were initially 95lb and 80lb springs and it rode level. I bumped that up to 110/80 and then 110/95 but it still won't come back up if fully compressed. I've played with the dual rate nuts so that the Jeep would sit on the lower spring at ride height but still nothing. The shocks are pumped up to 200psi as per Fox's recommendation.

Should I be trying stiffer springs still or try playing with the rebound washer stack? I've got the compression settings off the scale on the low end and it's still harsh hitting a bump.

It starts at normal ride height and will sit there until any forces act on it. When I push it down, it will stay there as well until something acts on it. You may have to pick a spot on the wall to reference the bumper height when I push/pull it.

https://www.youtube.com/watch?v=WThV...ture=emb_title
 

bdkw1

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Do you know what the current valving is?
 

Waternut

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Macon, GA
Do you know what the current valving is?

Here is a picture of standard valving chart (ignore the boxes). Stock valving when I got the shocks was #70 on rebound and #50 on compression and it was soul crushing to ride around on the street. After a couple iterations, I'm at #55 on rebound and off the scale on the light side of compression but it's still as stiff as a stock YJ with leaf springs and over inflated tires. I tried #40 compression and #35 before trying out a flutter stack. Compression is now set up with a flutter and is listed below:

1.60 - .006
1.10 - .010
1.42 - .006
1.35 - .008
.950 - .010
.800 - .020


Fox 2.0 Series Valving.png
 

SLOWPOKE693

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I think you need to run stiffer springs, they seem on the light side. How much preload do you apply to achieve ride height?
 

bdkw1

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Way to much rebound. Go to a 30 stack. How many bleed holes open?
 

Waternut

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Macon, GA
I think you need to run stiffer springs, they seem on the light side. How much preload do you apply to achieve ride height?

Well...that's the tricky part considering ride height is where it last decided to rest. Doesn't matter whether I dial in a couple inches of preload or leave them snugged up. The ride height kind of settles where it feels like it. My first set of springs were 175/130 and the Jeep sat about 5" too high in the rear. I mean... it wouldn't break the bank the step up to a 125 or 130 spring on the bottom. However, given how stiff it already feels, it might break my back. haha
 

Waternut

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Way to much rebound. Go to a 30 stack. How many bleed holes open?

I can certainly try a lower rebound before buying new springs. I'm not familiar with bleed holes. Is that just something with the internal piston? If so, it's unchanged from stock.
 

bdkw1

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Bleed holes are to let fluid bypass the shim stacks. They effect your low speed damping. Little chattery bumps. You will see them in the Piston. There will be spots for 3 or 4 of them depending on the Piston. Not all are drilled through. A standard Piston usually just has 1 drilled.
 

ThePanzerFuhrer

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I can certainly try a lower rebound before buying new springs. I'm not familiar with bleed holes. Is that just something with the internal piston? If so, it's unchanged from stock.

It should have a small bypass hole to let the shock fully rebound at rest.

I think you have 4 options.

increase spring rate which will make it ride like a lumber wagon

increase preload by 2-3”

move the shock mounts to reflect the tide height you want

stop taking your mom out on wheeling trips :flipoff2:

how I would fix this is buy a set of longer shocks to account for the droop to give you the correct ride height but also have a lower spring rate to improve ride quality. I like droop it keeps the tire on the ground.
 

Waternut

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Macon, GA
Well when I change the rebound stack, I can look at the bleed holes. The chattery bumps are the ones that kill me the most. If I go full steam at some large bumps, it doesn't seem to care. If there is only 1 bleed hole, should I drill 1-3 more?

If I go to a 16" shock, I'd be forced to cut into the tub and/or drop the shock mounts several inches below the axle tube. Considering the 14" shocks in the rear are fully flexed before the front leaf springs really start to articulate, more rear travel may not be the best thing.
 

ThePanzerFuhrer

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Well when I change the rebound stack, I can look at the bleed holes. The chattery bumps are the ones that kill me the most. If I go full steam at some large bumps, it doesn't seem to care. If there is only 1 bleed hole, should I drill 1-3 more?

If I go to a 16" shock, I'd be forced to cut into the tub and/or drop the shock mounts several inches below the axle tube. Considering the 14" shocks in the rear are fully flexed before the front leaf springs really start to articulate, more rear travel may not be the best thing.

In my experience the chattering bumps are controlled by the low speed holes. When I built the shocks for our minibaja cars we would test for this problem. We called it stack up when the shock did not have enough time to rebound and progressively got worse the more bumps you hit.

what we did was drill a larger 3/16 in hole down the shaft and then cross drilled below piston. We drilled and tapped the end to alow us to screw in set screws with various size orfice holes.
 

bdkw1

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Change the reb stack and drill 1 more hole. Don't get to carried away.
 

bdkw1

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My feelings are to much reb is sucking the rear down making it harsh. The softer comp stack and flutter made this worse.
 

Mac5005

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Need to get some preload if you don’t have any. Shoot for 2”. This gets some decent spring pressure all the way to droop. Otherwise the spring force is far to digressive.

light rebound valving, and I agree with drilling another bleed hole.

I have drill/tap/screws for #4, #6, #8 set screws. This way I already drill it to correct size, if I need to plug it it, I just run the tap in and install the set screw as block off.
 

Waternut

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Thanks everyone. I'll try to knock this out in a the next few days and report back.
 

Waternut

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This is what my damping piston looks like. Are those tiny little holes the bleed holes?

I'm going to have to order new shims since I don't have anything thin enough to get my rebound down low enough.

IMG_20200611_192220.jpg


IMG_20200611_192206.jpg
 

Waternut

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Small holes are the bleeds. Hard to tell in your pictures... Are there set screws in the holes or are they solid?

No set screws and only 2 holes are actually drilled through. The holes are roughly 3/32" and step down to 1/16".

Should I open up those 1/16" holes up to 3/32" or drill 1-2 more 1/16" holes in the existing 3/32" holes that aren't drilled all the way through?



On a side note... I'm ordering shims and the shocks are apart so maybe now is a good time to refresh the oil. The red oil is starting to get a bit blackish. I'm guessing the red oil is 7w. Think it'd be worth going down to a 5w oil considering the light level of valving in these shocks?
 

Beat95yj

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Fox does not use set screws in there 2.0’s. Drill one additional 1/16 hole and try it.
 

Waternut

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Just waiting on my shims at this point. However, I may have lost track of which way the damping piston is supposed to go. Anyone know which way is up/down?
 

bdkw1

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The side with the pre-drilled bleed holes is the rebound side.
 

Waternut

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Macon, GA
Ok so the parts finally came in and I got everything installed. Drilled one extra 1/16" hole in each damping piston. I also changed the fluid from the red 7w to the blue 5w. The rebound stack is a #30 and the compression stack would be a #20 if the chart kept going (from largest dia to smallest - .006, .006, .008, .008, .008, .020). Without the springs and low pressure, I confirmed that both shocks have smooth travel throughout the stroke. Pumped up both shocks to the required 200psi and I have 1.6" of preload on the springs.

After all of this, the ride seems be better but the shocks still have that weird zone of not wanting to return to a single position. If I lift it up, it stays there. If I push it down, it stays there. I guess it's only a couple inches of ride height change but a little weird nevertheless. I'm beginning to think that maybe this is normal but most people just have a heavier rig and they can't (or don't) lift it up like I'm doing.

I'd like to get another .75"-1.0" of ride height and since it seems to want to stay in the lower position, it seems like the real fix is between more preload and stiffer springs. I kind of feel like anything past 2" of preload is too much so please correct me if I'm wrong. If that's too much preload, that would lead me into new springs.
 
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